update

Reviewed-on: #7

Project.toml

@@ -1,6 +1,6 @@
 name = "NATSBridge"
 uuid = "f2724d33-f338-4a57-b9f8-1be882570d10"
-version = "0.4.2"
+version = "0.4.3"
 authors = ["narawat <narawat@gmail.com>"]
 
 [deps]

README.md

@@ -0,0 +1,968 @@
+# NATSBridge
+
+A high-performance, bi-directional data bridge between **Julia**, **JavaScript**, and **Python/Micropython** applications using NATS (Core & JetStream), implementing the Claim-Check pattern for large payloads.
+
+[![License: MIT](https://img.shields.io/badge/License-MIT-blue.svg)](https://opensource.org/licenses/MIT)
+[![NATS](https://img.shields.io/badge/NATS-Enabled-green.svg)](https://nats.io)
+
+---
+
+## Table of Contents
+
+- [Overview](#overview)
+- [Features](#features)
+- [Architecture](#architecture)
+- [Installation](#installation)
+- [Quick Start](#quick-start)
+- [API Reference](#api-reference)
+- [Payload Types](#payload-types)
+- [Transport Strategies](#transport-strategies)
+- [Examples](#examples)
+- [Testing](#testing)
+- [License](#license)
+
+---
+
+## Overview
+
+NATSBridge enables seamless communication across Julia, JavaScript, and Python/Micropython applications through NATS, with intelligent transport selection based on payload size:
+
+| Transport | Payload Size | Method |
+|-----------|--------------|--------|
+| **Direct** | < 1MB | Sent directly via NATS (Base64 encoded) |
+| **Link** | >= 1MB | Uploaded to HTTP file server, URL sent via NATS |
+
+### Use Cases
+
+- **Chat Applications**: Text, images, audio, video in a single message
+- **File Transfer**: Efficient transfer of large files using claim-check pattern
+- **Streaming Data**: Sensor data, telemetry, and analytics pipelines
+- **Cross-Platform Communication**: Julia ↔ JavaScript ↔ Python/Micropython
+- **IoT Devices**: Micropython devices sending data to cloud services
+
+---
+
+## Features
+
+- ✅ **Bi-directional messaging** between Julia, JavaScript, and Python/Micropython
+- ✅ **Multi-payload support** - send multiple payloads with different types in one message
+- ✅ **Automatic transport selection** - direct vs link based on payload size
+- ✅ **Claim-Check pattern** for payloads > 1MB
+- ✅ **Apache Arrow IPC** support for tabular data (zero-copy reading)
+- ✅ **Exponential backoff** for reliable file server downloads
+- ✅ **Correlation ID tracking** for message tracing
+- ✅ **Reply-to support** for request-response patterns
+- ✅ **JetStream support** for message replay and durability
+- ✅ **Lightweight Micropython implementation** for microcontrollers
+
+---
+
+## Architecture
+
+### System Components
+
+```
+┌─────────────────────────────────────────────────────────────────────┐
+│                     NATSBridge Architecture                         │
+├─────────────────────────────────────────────────────────────────────┤
+│  ┌──────────────┐    ┌──────────────┐    ┌──────────────┐           │
+│  │   Julia      │    │  JavaScript  │    │  Python/     │           │
+│  │  (NATS.jl)   │◄──►│  (nats.js)   │◄──►│  Micropython │           │
+│  └──────────────┘    └──────────────┘    └──────────────┘           │
+│       │                    │                    │                   │
+│       ▼                    ▼                    ▼                   │
+│    ┌─────────────────────────────────────────────────────┐          │
+│    │                    NATS                             │          │
+│    │               (Message Broker)                      │          │
+│    └─────────────────────────────────────────────────────┘          │
+│                              │                                      │
+│                              ▼                                      │
+│                    ┌──────────────────────┐                         │
+│                    │  File Server         │                         │
+│                    │  (HTTP Upload/Get)   │                         │
+│                    └──────────────────────┘                         │
+└─────────────────────────────────────────────────────────────────────┘
+```
+
+### Message Flow
+
+1. **Sender** creates a message envelope with payloads
+2. **NATSBridge** serializes and encodes payloads based on type
+3. **Transport Decision**: Small payloads go directly to NATS, large payloads are uploaded to file server
+4. **NATS** routes messages to subscribers
+5. **Receiver** fetches payloads (from NATS or file server)
+6. **NATSBridge** deserializes and decodes payloads
+
+---
+
+## Installation
+
+### Prerequisites
+
+- **NATS Server** (v2.10+ recommended)
+- **HTTP File Server** (optional, for payloads > 1MB)
+
+### Julia
+
+```julia
+using Pkg
+Pkg.add("NATS")
+Pkg.add("https://git.yiem.cc/ton/NATSBridge")
+```
+
+### JavaScript
+
+```bash
+npm install nats.js apache-arrow uuid base64-url
+```
+
+For Node.js:
+```javascript
+const { smartsend, smartreceive } = require('./src/NATSBridge');
+```
+
+For browser:
+```html
+<script src="./src/NATSBridge.js"></script>
+<script>
+  // NATSBridge is available as window.NATSBridge
+</script>
+```
+
+### Python/Micropython
+
+1. Copy [`src/nats_bridge.py`](src/nats_bridge.py) to your device
+2. Install dependencies:
+
+**For Python (desktop):**
+```bash
+pip install nats-py
+```
+
+**For Micropython:**
+- `urequests` for HTTP requests (built-in for ESP32)
+- `base64` for base64 encoding (built-in)
+- `json` for JSON handling (built-in)
+
+---
+
+## Quick Start
+
+### Step 1: Start NATS Server
+
+```bash
+docker run -p 4222:4222 nats:latest
+```
+
+### Step 2: Start HTTP File Server (Optional)
+
+```bash
+# Create a directory for file uploads
+mkdir -p /tmp/fileserver
+
+# Use Python's built-in server
+python3 -m http.server 8080 --directory /tmp/fileserver
+```
+
+### Step 3: Send Your First Message
+
+#### Python/Micropython
+
+```python
+from nats_bridge import smartsend
+
+# Send a text message
+data = [("message", "Hello World", "text")]
+env, env_json_str = smartsend("/chat/room1", data, nats_url="nats://localhost:4222")
+print("Message sent!")
+```
+
+#### JavaScript
+
+```javascript
+const { smartsend } = require('./src/NATSBridge');
+
+// Send a text message
+const { env, env_json_str } = await smartsend("/chat/room1", [
+    { dataname: "message", data: "Hello World", type: "text" }
+], { natsUrl: "nats://localhost:4222" });
+
+console.log("Message sent!");
+```
+
+#### Julia
+
+```julia
+using NATSBridge
+
+# Send a text message
+data = [("message", "Hello World", "text")]
+env, env_json_str = NATSBridge.smartsend("/chat/room1", data; nats_url="nats://localhost:4222")
+println("Message sent!")
+```
+
+### Step 4: Receive Messages
+
+#### Python/Micropython
+
+```python
+import nats
+import asyncio
+from nats_bridge import smartreceive
+
+# Configuration
+SUBJECT = "/chat/room1"
+NATS_URL = "nats://localhost:4222"
+
+async def main():
+    # Connect to NATS
+    nc = await nats.connect(NATS_URL)
+    
+    # Subscribe to the subject - msg comes from the callback
+    async def message_handler(msg):
+        # Receive and process message
+        env = smartreceive(msg.data)
+        for dataname, data, type in env["payloads"]:
+            print(f"Received {dataname}: {data}")
+    
+    sid = await nc.subscribe(SUBJECT, cb=message_handler)
+    await asyncio.sleep(120)  # Keep listening
+    await nc.close()
+
+asyncio.run(main())
+```
+
+#### JavaScript
+
+```javascript
+const { smartreceive } = require('./src/NATSBridge');
+const { connect } = require('nats');
+
+// Configuration
+const SUBJECT = "/chat/room1";
+const NATS_URL = "nats://localhost:4222";
+
+async function main() {
+    // Connect to NATS
+    const nc = await connect({ servers: [NATS_URL] });
+    
+    // Subscribe to the subject - msg comes from the async iteration
+    const sub = nc.subscribe(SUBJECT);
+    
+    for await (const msg of sub) {
+        // Receive and process message
+        const env = await smartreceive(msg);
+        for (const payload of env.payloads) {
+            console.log(`Received ${payload.dataname}: ${payload.data}`);
+        }
+    }
+}
+
+main();
+```
+
+#### Julia
+
+```julia
+using NATS, NATSBridge
+
+# Configuration
+const SUBJECT = "/chat/room1"
+const NATS_URL = "nats://localhost:4222"
+
+# Helper: Log with correlation ID
+function log_trace(message)
+    timestamp = Dates.now()
+    println("[$timestamp] $message")
+end
+
+# Receiver: Listen for messages - msg comes from the callback
+function test_receive()
+    conn = NATS.connect(NATS_URL)
+    NATS.subscribe(conn, SUBJECT) do msg
+        log_trace("Received message on $(msg.subject)")
+        
+        # Receive and process message
+        env, env_json_str = NATSBridge.smartreceive(msg, fileserverDownloadHandler)
+        for (dataname, data, type) in env["payloads"]
+            println("Received $dataname: $data")
+        end
+    end
+    
+    # Keep listening for 120 seconds
+    sleep(120)
+    NATS.drain(conn)
+end
+
+test_receive()
+```
+
+---
+
+## API Reference
+
+### smartsend
+
+Sends data either directly via NATS or via a fileserver URL, depending on payload size.
+
+#### Python/Micropython
+
+```python
+from nats_bridge import smartsend
+
+env, env_json_str = smartsend(
+    subject,                           # NATS subject to publish to
+    data,                              # List of (dataname, data, type) tuples
+    nats_url="nats://localhost:4222",  # NATS server URL
+    fileserver_url="http://localhost:8080",  # File server URL
+    fileserver_upload_handler=plik_oneshot_upload,  # Upload handler function
+    size_threshold=1_000_000,          # Threshold in bytes (default: 1MB)
+    correlation_id=None,               # Optional correlation ID for tracing
+    msg_purpose="chat",                # Message purpose
+    sender_name="NATSBridge",          # Sender name
+    receiver_name="",                  # Receiver name (empty = broadcast)
+    receiver_id="",                    # Receiver UUID (empty = broadcast)
+    reply_to="",                       # Reply topic
+    reply_to_msg_id="",                # Reply message ID
+    is_publish=True                    # Whether to automatically publish to NATS
+)
+```
+
+#### JavaScript
+
+```javascript
+const { smartsend } = require('./src/NATSBridge');
+
+const { env, env_json_str } = await smartsend(
+    subject,                           // NATS subject
+    data,                              // Array of {dataname, data, type}
+    {
+        natsUrl: "nats://localhost:4222",
+        fileserverUrl: "http://localhost:8080",
+        fileserverUploadHandler: customUploadHandler,
+        sizeThreshold: 1_000_000,
+        correlationId: "custom-id",
+        msgPurpose: "chat",
+        senderName: "NATSBridge",
+        receiverName: "",
+        receiverId: "",
+        replyTo: "",
+        replyToMsgId: "",
+        isPublish: true                  // Whether to automatically publish to NATS
+    }
+);
+```
+
+#### Julia
+
+```julia
+using NATSBridge
+
+env, env_json_str = NATSBridge.smartsend(
+    subject,                           # NATS subject
+    data::AbstractArray{Tuple{String, Any, String}};  # List of (dataname, data, type)
+    nats_url::String = "nats://localhost:4222",
+    fileserver_url = "http://localhost:8080",
+    fileserverUploadHandler::Function = plik_oneshot_upload,
+    size_threshold::Int = 1_000_000,
+    correlation_id::Union{String, Nothing} = nothing,
+    msg_purpose::String = "chat",
+    sender_name::String = "NATSBridge",
+    receiver_name::String = "",
+    receiver_id::String = "",
+    reply_to::String = "",
+    reply_to_msg_id::String = "",
+    is_publish::Bool = true            # Whether to automatically publish to NATS
+)
+# Returns: (msgEnvelope_v1, JSON string)
+# - env: msgEnvelope_v1 object with all envelope metadata and payloads
+# - env_json_str: JSON string representation of the envelope for publishing
+```
+
+### smartreceive
+
+Receives and processes messages from NATS, handling both direct and link transport.
+
+#### Python/Micropython
+
+```python
+from nats_bridge import smartreceive
+
+# Note: For nats-py, use msg.data to pass the raw message data
+env = smartreceive(
+    msg.data,                          # NATS message data (msg.data for nats-py)
+    fileserver_download_handler=_fetch_with_backoff,  # Download handler
+    max_retries=5,                     # Max retry attempts
+    base_delay=100,                    # Initial delay in ms
+    max_delay=5000                     # Max delay in ms
+)
+# Returns: Dict with envelope metadata and 'payloads' field
+```
+
+#### JavaScript
+
+```javascript
+const { smartreceive } = require('./src/NATSBridge');
+
+// Note: msg is the NATS message object from subscription
+const env = await smartreceive(
+    msg,                               // NATS message (raw object from subscription)
+    {
+        fileserverDownloadHandler: customDownloadHandler,
+        maxRetries: 5,
+        baseDelay: 100,
+        maxDelay: 5000
+    }
+);
+// Returns: Object with envelope metadata and payloads array
+```
+
+#### Julia
+
+```julia
+using NATSBridge
+
+# Note: msg is a NATS.Msg object passed from the subscription callback
+env, env_json_str = NATSBridge.smartreceive(
+    msg::NATS.Msg;
+    fileserverDownloadHandler::Function = _fetch_with_backoff,
+    max_retries::Int = 5,
+    base_delay::Int = 100,
+    max_delay::Int = 5000
+)
+# Returns: Dict with envelope metadata and payloads array
+```
+
+---
+
+## Payload Types
+
+| Type | Description | Serialization |
+|------|-------------|---------------|
+| `text` | Plain text strings | UTF-8 bytes |
+| `dictionary` | JSON-serializable dictionaries | JSON |
+| `table` | Tabular data (DataFrames, arrays) | Apache Arrow IPC |
+| `image` | Image data (PNG, JPG) | Raw bytes |
+| `audio` | Audio data (WAV, MP3) | Raw bytes |
+| `video` | Video data (MP4, AVI) | Raw bytes |
+| `binary` | Generic binary data | Raw bytes |
+
+---
+
+## Transport Strategies
+
+### Direct Transport (Payloads < 1MB)
+
+Small payloads are sent directly via NATS with Base64 encoding.
+
+#### Python/Micropython
+```python
+data = [("message", "Hello", "text")]
+smartsend("/topic", data)
+```
+
+#### JavaScript
+```javascript
+await smartsend("/topic", [
+    { dataname: "message", data: "Hello", type: "text" }
+]);
+```
+
+#### Julia
+```julia
+data = [("message", "Hello", "text")]
+smartsend("/topic", data)
+```
+
+### Link Transport (Payloads >= 1MB)
+
+Large payloads are uploaded to an HTTP file server.
+
+#### Python/Micropython
+```python
+data = [("file", large_data, "binary")]
+smartsend("/topic", data, fileserver_url="http://localhost:8080")
+```
+
+#### JavaScript
+```javascript
+await smartsend("/topic", [
+    { dataname: "file", data: largeData, type: "binary" }
+], { fileserverUrl: "http://localhost:8080" });
+```
+
+#### Julia
+```julia
+data = [("file", large_data, "binary")]
+smartsend("/topic", data; fileserver_url="http://localhost:8080")
+```
+
+---
+
+## Examples
+
+All examples include code for **Julia**, **JavaScript**, and **Python/Micropython** unless otherwise specified.
+
+### Example 1: Chat with Mixed Content
+
+Send text, small image, and large file in one message.
+
+#### Python/Micropython
+```python
+from nats_bridge import smartsend
+
+data = [
+    ("message_text", "Hello!", "text"),
+    ("user_avatar", image_data, "image"),
+    ("large_document", large_file_data, "binary")
+]
+
+env, env_json_str = smartsend("/chat/room1", data, fileserver_url="http://localhost:8080")
+```
+
+#### JavaScript
+```javascript
+const { smartsend } = require('./src/NATSBridge');
+
+const { env, env_json_str } = await smartsend("/chat/room1", [
+    { dataname: "message_text", data: "Hello!", type: "text" },
+    { dataname: "user_avatar", data: image_data, type: "image" },
+    { dataname: "large_document", data: large_file_data, type: "binary" }
+], {
+    fileserverUrl: "http://localhost:8080"
+});
+```
+
+#### Julia
+```julia
+using NATSBridge
+
+data = [
+    ("message_text", "Hello!", "text"),
+    ("user_avatar", image_data, "image"),
+    ("large_document", large_file_data, "binary")
+]
+
+env, env_json_str = NATSBridge.smartsend("/chat/room1", data; fileserver_url="http://localhost:8080")
+```
+
+### Example 2: Dictionary Exchange
+
+Send configuration data between platforms.
+
+#### Python/Micropython
+```python
+from nats_bridge import smartsend
+
+config = {
+    "wifi_ssid": "MyNetwork",
+    "wifi_password": "password123",
+    "update_interval": 60
+}
+
+data = [("config", config, "dictionary")]
+env, env_json_str = smartsend("/device/config", data)
+```
+
+#### JavaScript
+```javascript
+const { smartsend } = require('./src/NATSBridge');
+
+const config = {
+    wifi_ssid: "MyNetwork",
+    wifi_password: "password123",
+    update_interval: 60
+};
+
+const { env, env_json_str } = await smartsend("/device/config", [
+    { dataname: "config", data: config, type: "dictionary" }
+]);
+```
+
+#### Julia
+```julia
+using NATSBridge
+
+config = Dict(
+    "wifi_ssid" => "MyNetwork",
+    "wifi_password" => "password123",
+    "update_interval" => 60
+)
+
+data = [("config", config, "dictionary")]
+env, env_json_str = NATSBridge.smartsend("/device/config", data)
+```
+
+### Example 3: Table Data (Arrow IPC)
+
+Send tabular data using Apache Arrow IPC format.
+
+#### Python/Micropython
+```python
+import pandas as pd
+from nats_bridge import smartsend
+
+df = pd.DataFrame({
+    "id": [1, 2, 3],
+    "name": ["Alice", "Bob", "Charlie"],
+    "score": [95, 88, 92]
+})
+
+data = [("students", df, "table")]
+env, env_json_str = smartsend("/data/analysis", data)
+```
+
+#### JavaScript
+```javascript
+const { smartsend } = require('./src/NATSBridge');
+
+const tableData = [
+    { id: 1, name: "Alice", score: 95 },
+    { id: 2, name: "Bob", score: 88 },
+    { id: 3, name: "Charlie", score: 92 }
+];
+
+const { env, env_json_str } = await smartsend("/data/analysis", [
+    { dataname: "students", data: tableData, type: "table" }
+]);
+```
+
+#### Julia
+```julia
+using NATSBridge
+using DataFrames
+
+df = DataFrame(
+    id = [1, 2, 3],
+    name = ["Alice", "Bob", "Charlie"],
+    score = [95, 88, 92]
+)
+
+data = [("students", df, "table")]
+env, env_json_str = NATSBridge.smartsend("/data/analysis", data)
+```
+
+### Example 4: Request-Response Pattern with Envelope JSON
+
+Bi-directional communication with reply-to support. The `smartsend` function now returns both the envelope object and a JSON string that can be published directly.
+
+#### Python/Micropython (Requester)
+```python
+from nats_bridge import smartsend
+
+env, env_json_str = smartsend(
+    "/device/command",
+    [("command", {"action": "read_sensor"}, "dictionary")],
+    reply_to="/device/response"
+)
+# env: msgEnvelope_v1 object
+# env_json_str: JSON string for publishing to NATS
+
+# The env_json_str can also be published directly using NATS request-reply pattern
+# nc.request("/device/command", env_json_str, reply_to="/device/response")
+```
+
+#### Python/Micropython (Responder)
+```python
+import nats
+import asyncio
+from nats_bridge import smartreceive, smartsend
+
+# Configuration
+SUBJECT = "/device/command"
+REPLY_SUBJECT = "/device/response"
+NATS_URL = "nats://localhost:4222"
+
+async def main():
+    nc = await nats.connect(NATS_URL)
+    
+    async def message_handler(msg):
+        env = smartreceive(msg.data)
+        for dataname, data, type in env["payloads"]:
+            if data.get("action") == "read_sensor":
+                response = {"sensor_id": "sensor-001", "value": 42.5}
+                smartsend(REPLY_SUBJECT, [("data", response, "dictionary")])
+    
+    sid = await nc.subscribe(SUBJECT, cb=message_handler)
+    await asyncio.sleep(120)
+    await nc.close()
+
+asyncio.run(main())
+```
+
+#### JavaScript (Requester)
+```javascript
+const { smartsend } = require('./src/NATSBridge');
+
+const { env, env_json_str } = await smartsend("/device/command", [
+    { dataname: "command", data: { action: "read_sensor" }, type: "dictionary" }
+], {
+    replyTo: "/device/response"
+});
+```
+
+#### JavaScript (Responder)
+```javascript
+const { smartreceive, smartsend } = require('./src/NATSBridge');
+const { connect } = require('nats');
+
+// Configuration
+const SUBJECT = "/device/command";
+const REPLY_SUBJECT = "/device/response";
+const NATS_URL = "nats://localhost:4222";
+
+async function main() {
+    const nc = await connect({ servers: [NATS_URL] });
+    
+    const sub = nc.subscribe(SUBJECT);
+    
+    for await (const msg of sub) {
+        const env = await smartreceive(msg);
+        for (const payload of env.payloads) {
+            if (payload.dataname === "command" && payload.data.action === "read_sensor") {
+                const response = { sensor_id: "sensor-001", value: 42.5 };
+                await smartsend(REPLY_SUBJECT, [
+                    { dataname: "data", data: response, type: "dictionary" }
+                ]);
+            }
+        }
+    }
+}
+
+main();
+```
+
+#### Julia (Requester)
+```julia
+using NATSBridge
+
+env, env_json_str = NATSBridge.smartsend(
+    "/device/command",
+    [("command", Dict("action" => "read_sensor"), "dictionary")];
+    reply_to="/device/response"
+)
+```
+
+#### Julia (Responder)
+```julia
+using NATS, NATSBridge
+
+# Configuration
+const SUBJECT = "/device/command"
+const REPLY_SUBJECT = "/device/response"
+const NATS_URL = "nats://localhost:4222"
+
+function test_responder()
+    conn = NATS.connect(NATS_URL)
+    NATS.subscribe(conn, SUBJECT) do msg
+        env, env_json_str = NATSBridge.smartreceive(msg, fileserverDownloadHandler)
+        for (dataname, data, type) in env["payloads"]
+            if dataname == "command" && data["action"] == "read_sensor"
+                response = Dict("sensor_id" => "sensor-001", "value" => 42.5)
+                smartsend(REPLY_SUBJECT, [("data", response, "dictionary")])
+            end
+        end
+    end
+    
+    sleep(120)
+    NATS.drain(conn)
+end
+
+test_responder()
+```
+
+### Example 5: Micropython IoT Device
+
+Lightweight Micropython device sending sensor data.
+
+#### Micropython
+```python
+import nats
+import asyncio
+from nats_bridge import smartsend, smartreceive
+
+# Configuration
+SUBJECT = "/device/sensors"
+NATS_URL = "nats://localhost:4222"
+
+async def main():
+    nc = await nats.connect(NATS_URL)
+    
+    # Send sensor data
+    data = [("temperature", "25.5", "text"), ("humidity", 65, "dictionary")]
+    smartsend("/device/sensors", data, nats_url="nats://localhost:4222")
+    
+    # Receive commands - msg comes from the callback
+    async def message_handler(msg):
+        env = smartreceive(msg.data)
+        for dataname, data, type in env["payloads"]:
+            if type == "dictionary" and data.get("action") == "reboot":
+                # Execute reboot
+                pass
+    
+    sid = await nc.subscribe(SUBJECT, cb=message_handler)
+    await asyncio.sleep(120)
+    await nc.close()
+
+asyncio.run(main())
+```
+
+#### JavaScript (Receiver)
+```javascript
+const { smartreceive } = require('./src/NATSBridge');
+const { connect } = require('nats');
+
+// Configuration
+const SUBJECT = "/device/sensors";
+const NATS_URL = "nats://localhost:4222";
+
+async function main() {
+    const nc = await connect({ servers: [NATS_URL] });
+    
+    const sub = nc.subscribe(SUBJECT);
+    
+    for await (const msg of sub) {
+        const env = await smartreceive(msg);
+        for (const payload of env.payloads) {
+            if (payload.dataname === "temperature") {
+                console.log(`Temperature: ${payload.data}`);
+            } else if (payload.dataname === "humidity") {
+                console.log(`Humidity: ${payload.data}`);
+            }
+        }
+    }
+}
+
+main();
+```
+
+#### Julia (Receiver)
+```julia
+using NATS, NATSBridge
+
+# Configuration
+const SUBJECT = "/device/sensors"
+const NATS_URL = "nats://localhost:4222"
+
+function test_receiver()
+    conn = NATS.connect(NATS_URL)
+    NATS.subscribe(conn, SUBJECT) do msg
+        env, env_json_str = NATSBridge.smartreceive(msg, fileserverDownloadHandler)
+        for (dataname, data, type) in env["payloads"]
+            if dataname == "temperature"
+                println("Temperature: $data")
+            elseif dataname == "humidity"
+                println("Humidity: $data")
+            end
+        end
+    end
+    
+    sleep(120)
+    NATS.drain(conn)
+end
+
+test_receiver()
+```
+
+---
+
+## Testing
+
+Run the test scripts to verify functionality:
+
+### Python/Micropython
+
+```bash
+# Basic functionality test
+python test/test_micropython_basic.py
+
+# Text message exchange
+python test/test_micropython_text_sender.py
+python test/test_micropython_text_receiver.py
+
+# Dictionary exchange
+python test/test_micropython_dict_sender.py
+python test/test_micropython_dict_receiver.py
+
+# File transfer
+python test/test_micropython_file_sender.py
+python test/test_micropython_file_receiver.py
+
+# Mixed payload types
+python test/test_micropython_mixed_sender.py
+python test/test_micropython_mixed_receiver.py
+```
+
+### JavaScript
+
+```bash
+# Text message exchange
+node test/test_js_text_sender.js
+node test/test_js_text_receiver.js
+
+# Dictionary exchange
+node test/test_js_dict_sender.js
+node test/test_js_dict_receiver.js
+
+# File transfer
+node test/test_js_file_sender.js
+node test/test_js_file_receiver.js
+
+# Mixed payload types
+node test/test_js_mix_payload_sender.js
+node test/test_js_mix_payloads_receiver.js
+
+# Table exchange
+node test/test_js_table_sender.js
+node test/test_js_table_receiver.js
+```
+
+### Julia
+
+```julia
+# Text message exchange
+julia test/test_julia_text_sender.jl
+julia test/test_julia_text_receiver.jl
+
+# Dictionary exchange
+julia test/test_julia_dict_sender.jl
+julia test/test_julia_dict_receiver.jl
+
+# File transfer
+julia test/test_julia_file_sender.jl
+julia test/test_julia_file_receiver.jl
+
+# Mixed payload types
+julia test/test_julia_mix_payloads_sender.jl
+julia test/test_julia_mix_payloads_receiver.jl
+
+# Table exchange
+julia test/test_julia_table_sender.jl
+julia test/test_julia_table_receiver.jl
+```
+
+---
+
+## License
+
+MIT License
+
+Copyright (c) 2026 NATSBridge Contributors
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

docs/architecture.md

@@ -17,16 +17,16 @@ The system uses **handler functions** to abstract file server operations, allowi
 
 ```julia
 # Upload handler - uploads data to file server and returns URL
-# The handler is passed to smartsend as fileserverUploadHandler parameter
-# It receives: (fileserver_url::String, dataname::String, data::Vector{UInt8})
+# The handler is passed to smartsend as fileserver_upload_handler parameter
+# It receives: (file_server_url::String, dataname::String, data::Vector{UInt8})
 # Returns: Dict{String, Any} with keys: "status", "uploadid", "fileid", "url"
-fileserverUploadHandler(fileserver_url::String, dataname::String, data::Vector{UInt8})::Dict{String, Any}
+fileserver_upload_handler(file_server_url::String, dataname::String, data::Vector{UInt8})::Dict{String, Any}
 
 # Download handler - fetches data from file server URL with exponential backoff
-# The handler is passed to smartreceive as fileserverDownloadHandler parameter
+# The handler is passed to smartreceive as fileserver_download_handler parameter
 # It receives: (url::String, max_retries::Int, base_delay::Int, max_delay::Int, correlation_id::String)
 # Returns: Vector{UInt8} (the downloaded data)
-fileserverDownloadHandler(url::String, max_retries::Int, base_delay::Int, max_delay::Int, correlation_id::String)::Vector{UInt8}
+fileserver_download_handler(url::String, max_retries::Int, base_delay::Int, max_delay::Int, correlation_id::String)::Vector{UInt8}
 ```
 
 This design allows the system to support multiple file server backends without changing the core messaging logic.
@@ -40,21 +40,21 @@ The system uses a **standardized list-of-tuples format** for all payload operati
 # Input format for smartsend (always a list of tuples with type info)
 [(dataname1, data1, type1), (dataname2, data2, type2), ...]
 
-# Output format for smartreceive (returns envelope dictionary with payloads field)
-# Returns: Dict with envelope metadata and payloads field containing list of tuples
+# Output format for smartreceive (returns a dictionary with payloads field containing list of tuples)
+# Returns: Dict with envelope metadata and payloads field containing Vector{Tuple{String, Any, String}}
 # {
-#   "correlationId": "...",
-#   "msgId": "...",
+#   "correlation_id": "...",
+#   "msg_id": "...",
 #   "timestamp": "...",
-#   "sendTo": "...",
-#   "msgPurpose": "...",
-#   "senderName": "...",
-#   "senderId": "...",
-#   "receiverName": "...",
-#   "receiverId": "...",
-#   "replyTo": "...",
-#   "replyToMsgId": "...",
-#   "brokerURL": "...",
+#   "send_to": "...",
+#   "msg_purpose": "...",
+#   "sender_name": "...",
+#   "sender_id": "...",
+#   "receiver_name": "...",
+#   "receiver_id": "...",
+#   "reply_to": "...",
+#   "reply_to_msg_id": "...",
+#   "broker_url": "...",
 #   "metadata": {...},
 #   "payloads": [(dataname1, data1, type1), (dataname2, data2, type2), ...]
 # }
@@ -78,17 +78,16 @@ This design allows per-payload type specification, enabling **mixed-content mess
 smartsend(
     "/test",
     [("dataname1", data1, "dictionary")],  # List with one tuple (data, type)
-    nats_url="nats://localhost:4222",
-    fileserverUploadHandler=plik_oneshot_upload,
-    metadata=user_provided_envelope_level_metadata
+    broker_url="nats://localhost:4222",
+    fileserver_upload_handler=plik_oneshot_upload
 )
 
 # Multiple payloads in one message with different types
 smartsend(
     "/test",
     [("dataname1", data1, "dictionary"), ("dataname2", data2, "table")],
-    nats_url="nats://localhost:4222",
-    fileserverUploadHandler=plik_oneshot_upload
+    broker_url="nats://localhost:4222",
+    fileserver_upload_handler=plik_oneshot_upload
 )
 
 # Mixed content (e.g., chat with text, image, audio)
@@ -99,13 +98,14 @@ smartsend(
         ("user_image", image_data, "image"),
         ("audio_clip", audio_data, "audio")
     ],
-    nats_url="nats://localhost:4222"
+    broker_url="nats://localhost:4222"
 )
 
 # Receive returns a dictionary envelope with all metadata and deserialized payloads
-envelope = smartreceive(msg, fileserverDownloadHandler, max_retries, base_delay, max_delay)
-# envelope["payloads"] = [("dataname1", data1, type1), ("dataname2", data2, type2), ...]
-# envelope["correlationId"], envelope["msgId"], etc.
+env = smartreceive(msg; fileserver_download_handler=_fetch_with_backoff, max_retries=5, base_delay=100, max_delay=5000)
+# env["payloads"] = [("dataname1", data1, type1), ("dataname2", data2, type2), ...]
+# env["correlation_id"], env["msg_id"], etc.
+# env is a dictionary containing envelope metadata and payloads field
 ```
 
 ## Architecture Diagram
@@ -138,48 +138,48 @@ flowchart TD
 
 ## System Components
 
-### 1. msgEnvelope_v1 - Message Envelope
+### 1. msg_envelope_v1 - Message Envelope
 
-The `msgEnvelope_v1` structure provides a comprehensive message format for bidirectional communication between Julia, JavaScript, and Python/Micropython applications.
+The `msg_envelope_v1` structure provides a comprehensive message format for bidirectional communication between Julia, JavaScript, and Python/Micropython applications.
 
 **Julia Structure:**
 ```julia
-struct msgEnvelope_v1
-  correlationId::String       # Unique identifier to track messages across systems
-  msgId::String               # This message id
-  timestamp::String           # Message published timestamp
+struct msg_envelope_v1
+  correlation_id::String       # Unique identifier to track messages across systems
+  msg_id::String               # This message id
+  timestamp::String            # Message published timestamp
   
-  sendTo::String              # Topic/subject the sender sends to
-  msgPurpose::String          # Purpose of this message (ACK | NACK | updateStatus | shutdown | ...)
-  senderName::String          # Sender name (e.g., "agent-wine-web-frontend")
-  senderId::String            # Sender id (uuid4)
-  receiverName::String        # Message receiver name (e.g., "agent-backend")
-  receiverId::String          # Message receiver id (uuid4 or nothing for broadcast)
-  replyTo::String             # Topic to reply to
-  replyToMsgId::String        # Message id this message is replying to
-  brokerURL::String           # NATS server address
+  send_to::String              # Topic/subject the sender sends to
+  msg_purpose::String          # Purpose of this message (ACK | NACK | updateStatus | shutdown | ...)
+  sender_name::String          # Sender name (e.g., "agent-wine-web-frontend")
+  sender_id::String            # Sender id (uuid4)
+  receiver_name::String        # Message receiver name (e.g., "agent-backend")
+  receiver_id::String          # Message receiver id (uuid4 or nothing for broadcast)
+  reply_to::String             # Topic to reply to
+  reply_to_msg_id::String      # Message id this message is replying to
+  broker_url::String           # NATS server address
   
   metadata::Dict{String, Any}
-  payloads::AbstractArray{msgPayload_v1}  # Multiple payloads stored here
+  payloads::Vector{msg_payload_v1}  # Multiple payloads stored here
 end
 ```
 
 **JSON Schema:**
 ```json
 {
-  "correlationId": "uuid-v4-string",
-  "msgId": "uuid-v4-string",
+  "correlation_id": "uuid-v4-string",
+  "msg_id": "uuid-v4-string",
   "timestamp": "2024-01-15T10:30:00Z",
   
-  "sendTo": "topic/subject",
-  "msgPurpose": "ACK | NACK | updateStatus | shutdown | chat",
-  "senderName": "agent-wine-web-frontend",
-  "senderId": "uuid4",
-  "receiverName": "agent-backend",
-  "receiverId": "uuid4",
-  "replyTo": "topic",
-  "replyToMsgId": "uuid4",
-  "brokerURL": "nats://localhost:4222",
+  "send_to": "topic/subject",
+  "msg_purpose": "ACK | NACK | updateStatus | shutdown | chat",
+  "sender_name": "agent-wine-web-frontend",
+  "sender_id": "uuid4",
+  "receiver_name": "agent-backend",
+  "receiver_id": "uuid4",
+  "reply_to": "topic",
+  "reply_to_msg_id": "uuid4",
+  "broker_url": "nats://localhost:4222",
   
   "metadata": {
 
@@ -189,7 +189,7 @@ end
     {
       "id": "uuid4",
       "dataname": "login_image",
-      "type": "image",
+      "payload_type": "image",
       "transport": "direct",
       "encoding": "base64",
       "size": 15433,
@@ -201,7 +201,7 @@ end
     {
       "id": "uuid4",
       "dataname": "large_data",
-      "type": "table",
+      "payload_type": "table",
       "transport": "link",
       "encoding": "none",
       "size": 524288,
@@ -214,16 +214,16 @@ end
 }
 ```
 
-### 2. msgPayload_v1 - Payload Structure
+### 2. msg_payload_v1 - Payload Structure
 
-The `msgPayload_v1` structure provides flexible payload handling for various data types across all supported platforms.
+The `msg_payload_v1` structure provides flexible payload handling for various data types across all supported platforms.
 
 **Julia Structure:**
 ```julia
-struct msgPayload_v1
+struct msg_payload_v1
   id::String                    # Id of this payload (e.g., "uuid4")
   dataname::String              # Name of this payload (e.g., "login_image")
-  type::String                  # "text | dictionary | table | image | audio | video | binary"
+  payload_type::String          # "text | dictionary | table | image | audio | video | binary"
   transport::String             # "direct | link"
   encoding::String              # "none | json | base64 | arrow-ipc"
   size::Integer                 # Data size in bytes
@@ -383,13 +383,32 @@ graph TD
 ```julia
 function smartsend(
   subject::String,
-  data::AbstractArray{Tuple{String, Any, String}};  # No standalone type parameter
-  nats_url::String = "nats://localhost:4222",
-  fileserverUploadHandler::Function = plik_oneshot_upload,
-  size_threshold::Int = 1_000_000  # 1MB
+  data::AbstractArray{Tuple{String, Any, String}, 1};  # List of (dataname, data, type) tuples
+  broker_url::String = DEFAULT_BROKER_URL,  # NATS server URL
+  fileserver_url = DEFAULT_FILESERVER_URL,
+  fileserver_upload_handler::Function = plik_oneshot_upload,
+  size_threshold::Int = DEFAULT_SIZE_THRESHOLD,
+  correlation_id::Union{String, Nothing} = nothing,
+  msg_purpose::String = "chat",
+  sender_name::String = "NATSBridge",
+  receiver_name::String = "",
+  receiver_id::String = "",
+  reply_to::String = "",
+  reply_to_msg_id::String = "",
+  is_publish::Bool = true   # Whether to automatically publish to NATS
 )
 ```
 
+**Return Value:**
+- Returns a tuple `(env, env_json_str)` where:
+  - `env::msg_envelope_v1` - The envelope object containing all metadata and payloads
+  - `env_json_str::String` - JSON string representation of the envelope for publishing
+
+**Options:**
+- `is_publish::Bool = true` - When `true` (default), the message is automatically published to NATS. When `false`, the function returns the envelope and JSON string without publishing, allowing manual publishing via NATS request-reply pattern.
+
+The envelope object can be accessed directly for programmatic use, while the JSON string can be published directly to NATS using the request-reply pattern.
+
 **Input Format:**
 - `data::AbstractArray{Tuple{String, Any, String}}` - **Must be a list of (dataname, data, type) tuples**: `[("dataname1", data1, "type1"), ("dataname2", data2, "type2"), ...]`
 - Even for single payloads: `[(dataname1, data1, "type1")]`
@@ -406,8 +425,8 @@ function smartsend(
 
 ```julia
 function smartreceive(
-    msg::NATS.Message,
-    fileserverDownloadHandler::Function;
+    msg::NATS.Msg;
+    fileserver_download_handler::Function = _fetch_with_backoff,
     max_retries::Int = 5,
     base_delay::Int = 100,
     max_delay::Int = 5000
@@ -416,7 +435,7 @@ function smartreceive(
     # Iterate through all payloads
     # For each payload: check transport type
     #   If direct: decode Base64 payload
-    #   If link: fetch from URL with exponential backoff using fileserverDownloadHandler
+    #   If link: fetch from URL with exponential backoff using fileserver_download_handler
     # Deserialize payload based on type
     # Return envelope dictionary with all metadata and deserialized payloads
 end
@@ -424,7 +443,7 @@ end
 
 **Output Format:**
 - Returns a dictionary (key-value map) containing all envelope fields:
-  - `correlationId`, `msgId`, `timestamp`, `sendTo`, `msgPurpose`, `senderName`, `senderId`, `receiverName`, `receiverId`, `replyTo`, `replyToMsgId`, `brokerURL`
+  - `correlation_id`, `msg_id`, `timestamp`, `send_to`, `msg_purpose`, `sender_name`, `sender_id`, `receiver_name`, `receiver_id`, `reply_to`, `reply_to_msg_id`, `broker_url`
   - `metadata` - Message-level metadata dictionary
   - `payloads` - List of dictionaries, each containing deserialized payload data
 
@@ -434,71 +453,186 @@ end
 3. For each payload:
    - Determine transport type (`direct` or `link`)
    - If `direct`: decode Base64 data from the message
-   - If `link`: fetch data from URL using exponential backoff (via `fileserverDownloadHandler`)
+   - If `link`: fetch data from URL using exponential backoff (via `fileserver_download_handler`)
    - Deserialize based on payload type (`dictionary`, `table`, `binary`, etc.)
 4. Return envelope dictionary with `payloads` field containing list of `(dataname, data, type)` tuples
 
-**Note:** The `fileserverDownloadHandler` receives `(url::String, max_retries::Int, base_delay::Int, max_delay::Int, correlation_id::String)` and returns `Vector{UInt8}`.
+**Note:** The `fileserver_download_handler` receives `(url::String, max_retries::Int, base_delay::Int, max_delay::Int, correlation_id::String)` and returns `Vector{UInt8}`.
 
 ### JavaScript Implementation
 
 #### Dependencies
 - `nats.js` - Core NATS functionality
 - `apache-arrow` - Arrow IPC serialization
-- `uuid` - Correlation ID generation
+- `uuid` - Correlation ID and message ID generation
+- `base64-arraybuffer` - Base64 encoding/decoding
+- `node-fetch` or `fetch` - HTTP client for file server
 
 #### smartsend Function
 
 ```javascript
-async function smartsend(subject, data, options = {})
-    // data format: [(dataname, data, type), ...]
-    // options object should include:
-    // - natsUrl: NATS server URL
-    // - fileserverUrl: base URL of the file server
-    // - sizeThreshold: threshold in bytes for transport selection
-    // - correlationId: optional correlation ID for tracing
+async function smartsend(
+  subject,
+  data,  // List of (dataname, data, type) tuples: [(dataname1, data1, type1), ...]
+  options = {}
+)
 ```
 
+**Options:**
+- `broker_url` (String) - NATS server URL (default: `"nats://localhost:4222"`)
+- `fileserver_url` (String) - Base URL of the file server (default: `"http://localhost:8080"`)
+- `size_threshold` (Number) - Threshold in bytes for transport selection (default: `1048576` = 1MB)
+- `correlation_id` (String) - Optional correlation ID for tracing
+- `msg_purpose` (String) - Purpose of the message (default: `"chat"`)
+- `sender_name` (String) - Sender name (default: `"NATSBridge"`)
+- `receiver_name` (String) - Message receiver name (default: `""`)
+- `receiver_id` (String) - Message receiver ID (default: `""`)
+- `reply_to` (String) - Topic to reply to (default: `""`)
+- `reply_to_msg_id` (String) - Message ID this message is replying to (default: `""`)
+- `fileserver_upload_handler` (Function) - Custom upload handler function
+
+**Return Value:**
+- Returns a Promise that resolves to an object containing:
+  - `env` - The envelope object containing all metadata and payloads
+  - `env_json_str` - JSON string representation of the envelope for publishing
+  - `published` - Boolean indicating whether the message was automatically published to NATS
+
 **Input Format:**
 - `data` - **Must be a list of (dataname, data, type) tuples**: `[(dataname1, data1, "type1"), (dataname2, data2, "type2"), ...]`
 - Even for single payloads: `[(dataname1, data1, "type1")]`
 - Each payload can have a different type, enabling mixed-content messages
+- Supported types: `"text"`, `"dictionary"`, `"table"`, `"image"`, `"audio"`, `"video"`, `"binary"`
 
 **Flow:**
-1. Iterate through the list of (dataname, data, type) tuples
-2. For each payload: extract the type from the tuple and serialize accordingly
-3. Check payload size
-4. If < threshold: publish directly to NATS
-5. If >= threshold: upload to HTTP server, publish NATS with URL
+1. Generate correlation ID and message ID if not provided
+2. Iterate through the list of `(dataname, data, type)` tuples
+3. For each payload:
+   - Serialize based on payload type
+   - Check payload size
+   - If < threshold: Base64 encode and include in envelope
+   - If >= threshold: Upload to HTTP server, store URL in envelope
+4. Publish the JSON envelope to NATS
+5. Return envelope object and JSON string
 
 #### smartreceive Handler
 
 ```javascript
 async function smartreceive(msg, options = {})
-    // options object should include:
-    // - fileserverDownloadHandler: function to fetch data from file server URL
-    // - max_retries: maximum retry attempts for fetching URL
-    // - base_delay: initial delay for exponential backoff in ms
-    // - max_delay: maximum delay for exponential backoff in ms
-    // - correlationId: optional correlation ID for tracing
 ```
 
+**Options:**
+- `fileserver_download_handler` (Function) - Custom download handler function
+- `max_retries` (Number) - Maximum retry attempts for fetching URL (default: `5`)
+- `base_delay` (Number) - Initial delay for exponential backoff in ms (default: `100`)
+- `max_delay` (Number) - Maximum delay for exponential backoff in ms (default: `5000`)
+- `correlation_id` (String) - Optional correlation ID for tracing
+
 **Output Format:**
-- Returns a dictionary (key-value map) containing all envelope fields:
-  - `correlationId`, `msgId`, `timestamp`, `sendTo`, `msgPurpose`, `senderName`, `senderId`, `receiverName`, `receiverId`, `replyTo`, `replyToMsgId`, `brokerURL`
+- Returns a Promise that resolves to an object containing all envelope fields:
+  - `correlation_id`, `msg_id`, `timestamp`, `send_to`, `msg_purpose`, `sender_name`, `sender_id`, `receiver_name`, `receiver_id`, `reply_to`, `reply_to_msg_id`, `broker_url`
   - `metadata` - Message-level metadata dictionary
-  - `payloads` - List of dictionaries, each containing deserialized payload data
+  - `payloads` - List of dictionaries, each containing deserialized payload data with keys: `dataname`, `data`, `payload_type`
 
 **Process Flow:**
 1. Parse the JSON envelope to extract all fields
-2. Iterate through each payload in `payloads`
+2. Iterate through each payload in `payloads` array
 3. For each payload:
    - Determine transport type (`direct` or `link`)
-   - If `direct`: decode Base64 data from the message
-   - If `link`: fetch data from URL using exponential backoff
+   - If `direct`: Base64 decode the data from the message
+   - If `link`: Fetch data from URL using exponential backoff (via `fileserver_download_handler`)
+   - Deserialize based on payload type (`dictionary`, `table`, `binary`, etc.)
+4. Return envelope object with `payloads` field containing list of `(dataname, data, type)` tuples
+
+**Note:** The `fileserver_download_handler` receives `(url, max_retries, base_delay, max_delay, correlation_id)` and returns `ArrayBuffer` or `Uint8Array`.
+
+### Python/Micropython Implementation
+
+#### Dependencies
+- `nats-python` - Core NATS functionality
+- `pyarrow` - Arrow IPC serialization
+- `uuid` - Correlation ID and message ID generation
+- `base64` - Base64 encoding/decoding
+- `requests` or `aiohttp` - HTTP client for file server
+
+#### smartsend Function
+
+```python
+async def smartsend(
+    subject: str,
+    data: List[Tuple[str, Any, str]],  # List of (dataname, data, type) tuples
+    options: Dict = {}
+)
+```
+
+**Options:**
+- `broker_url` (str) - NATS server URL (default: `"nats://localhost:4222"`)
+- `fileserver_url` (str) - Base URL of the file server (default: `"http://localhost:8080"`)
+- `size_threshold` (int) - Threshold in bytes for transport selection (default: `1048576` = 1MB)
+- `correlation_id` (str) - Optional correlation ID for tracing
+- `msg_purpose` (str) - Purpose of the message (default: `"chat"`)
+- `sender_name` (str) - Sender name (default: `"NATSBridge"`)
+- `receiver_name` (str) - Message receiver name (default: `""`)
+- `receiver_id` (str) - Message receiver ID (default: `""`)
+- `reply_to` (str) - Topic to reply to (default: `""`)
+- `reply_to_msg_id` (str) - Message ID this message is replying to (default: `""`)
+- `fileserver_upload_handler` (Callable) - Custom upload handler function
+
+**Return Value:**
+- Returns a tuple `(env, env_json_str)` where:
+  - `env` - The envelope dictionary containing all metadata and payloads
+  - `env_json_str` - JSON string representation of the envelope for publishing
+
+**Input Format:**
+- `data` - **Must be a list of (dataname, data, type) tuples**: `[(dataname1, data1, "type1"), (dataname2, data2, "type2"), ...]`
+- Even for single payloads: `[(dataname1, data1, "type1")]`
+- Each payload can have a different type, enabling mixed-content messages
+- Supported types: `"text"`, `"dictionary"`, `"table"`, `"image"`, `"audio"`, `"video"`, `"binary"`
+
+**Flow:**
+1. Generate correlation ID and message ID if not provided
+2. Iterate through the list of `(dataname, data, type)` tuples
+3. For each payload:
+   - Serialize based on payload type
+   - Check payload size
+   - If < threshold: Base64 encode and include in envelope
+   - If >= threshold: Upload to HTTP server, store URL in envelope
+4. Publish the JSON envelope to NATS
+5. Return envelope dictionary and JSON string
+
+#### smartreceive Handler
+
+```python
+async def smartreceive(
+    msg: NATS.Message,
+    options: Dict = {}
+)
+```
+
+**Options:**
+- `fileserver_download_handler` (Callable) - Custom download handler function
+- `max_retries` (int) - Maximum retry attempts for fetching URL (default: `5`)
+- `base_delay` (int) - Initial delay for exponential backoff in ms (default: `100`)
+- `max_delay` (int) - Maximum delay for exponential backoff in ms (default: `5000`)
+- `correlation_id` (str) - Optional correlation ID for tracing
+
+**Output Format:**
+- Returns a dictionary containing all envelope fields:
+  - `correlation_id`, `msg_id`, `timestamp`, `send_to`, `msg_purpose`, `sender_name`, `sender_id`, `receiver_name`, `receiver_id`, `reply_to`, `reply_to_msg_id`, `broker_url`
+  - `metadata` - Message-level metadata dictionary
+  - `payloads` - List of tuples, each containing `(dataname, data, payload_type)` with deserialized payload data
+
+**Process Flow:**
+1. Parse the JSON envelope to extract all fields
+2. Iterate through each payload in `payloads` list
+3. For each payload:
+   - Determine transport type (`direct` or `link`)
+   - If `direct`: Base64 decode the data from the message
+   - If `link`: Fetch data from URL using exponential backoff (via `fileserver_download_handler`)
    - Deserialize based on payload type (`dictionary`, `table`, `binary`, etc.)
 4. Return envelope dictionary with `payloads` field containing list of `(dataname, data, type)` tuples
 
+**Note:** The `fileserver_download_handler` receives `(url: str, max_retries: int, base_delay: int, max_delay: int, correlation_id: str)` and returns `bytes`.
+
 ## Scenario Implementations
 
 ### Scenario 1: Command & Control (Small Dictionary)

docs/implementation.md

@@ -19,49 +19,102 @@ NATSBridge is implemented in three languages, each providing the same API:
 | **JavaScript** | [`src/NATSBridge.js`](../src/NATSBridge.js) | JavaScript implementation for Node.js and browsers |
 | **Python/Micropython** | [`src/nats_bridge.py`](../src/nats_bridge.py) | Python implementation for desktop and microcontrollers |
 
-### Multi-Payload Support
+### File Server Handler Architecture
 
-The implementation uses a **standardized list-of-tuples format** for all payload operations. **Even when sending a single payload, the user must wrap it in a list.**
+The system uses **handler functions** to abstract file server operations, allowing support for different file server implementations (e.g., Plik, AWS S3, custom HTTP server).
+
+**Handler Function Signatures:**
+
+```julia
+# Upload handler - uploads data to file server and returns URL
+# The handler is passed to smartsend as fileserver_upload_handler parameter
+# It receives: (file_server_url::String, dataname::String, data::Vector{UInt8})
+# Returns: Dict{String, Any} with keys: "status", "uploadid", "fileid", "url"
+fileserver_upload_handler(file_server_url::String, dataname::String, data::Vector{UInt8})::Dict{String, Any}
+
+# Download handler - fetches data from file server URL with exponential backoff
+# The handler is passed to smartreceive as fileserver_download_handler parameter
+# It receives: (url::String, max_retries::Int, base_delay::Int, max_delay::Int, correlation_id::String)
+# Returns: Vector{UInt8} (the downloaded data)
+fileserver_download_handler(url::String, max_retries::Int, base_delay::Int, max_delay::Int, correlation_id::String)::Vector{UInt8}
+```
+
+This design allows the system to support multiple file server backends without changing the core messaging logic.
+
+### Multi-Payload Support (Standard API)
+
+The system uses a **standardized list-of-tuples format** for all payload operations. **Even when sending a single payload, the user must wrap it in a list.**
 
 **API Standard:**
 ```julia
 # Input format for smartsend (always a list of tuples with type info)
 [(dataname1, data1, type1), (dataname2, data2, type2), ...]
 
-# Output format for smartreceive (returns envelope dictionary with payloads field)
-# Returns: Dict with envelope metadata and payloads field containing list of tuples
+# Output format for smartreceive (returns a dictionary with payloads field containing list of tuples)
+# Returns: Dict with envelope metadata and payloads field containing Vector{Tuple{String, Any, String}}
 # {
-#   "correlationId": "...",
-#   "msgId": "...",
+#   "correlation_id": "...",
+#   "msg_id": "...",
 #   "timestamp": "...",
-#   "sendTo": "...",
-#   "msgPurpose": "...",
-#   "senderName": "...",
-#   "senderId": "...",
-#   "receiverName": "...",
-#   "receiverId": "...",
-#   "replyTo": "...",
-#   "replyToMsgId": "...",
-#   "brokerURL": "...",
+#   "send_to": "...",
+#   "msg_purpose": "...",
+#   "sender_name": "...",
+#   "sender_id": "...",
+#   "receiver_name": "...",
+#   "receiver_id": "...",
+#   "reply_to": "...",
+#   "reply_to_msg_id": "...",
+#   "broker_url": "...",
 #   "metadata": {...},
 #   "payloads": [(dataname1, data1, type1), (dataname2, data2, type2), ...]
 # }
 ```
 
-Where `type` can be: `"text"`, `"dictionary"`, `"table"`, `"image"`, `"audio"`, `"video"`, `"binary"`
+**Supported Types:**
+- `"text"` - Plain text
+- `"dictionary"` - JSON-serializable dictionaries (Dict, NamedTuple)
+- `"table"` - Tabular data (DataFrame, array of structs)
+- `"image"` - Image data (Bitmap, PNG/JPG bytes)
+- `"audio"` - Audio data (WAV, MP3 bytes)
+- `"video"` - Video data (MP4, AVI bytes)
+- `"binary"` - Generic binary data (Vector{UInt8})
+
+This design allows per-payload type specification, enabling **mixed-content messages** where different payloads can use different serialization formats in a single message.
 
 **Examples:**
 ```julia
-# Single payload - still wrapped in a list (type is required as third element)
-smartsend("/test", [(dataname1, data1, "text")], ...)
+# Single payload - still wrapped in a list
+smartsend(
+    "/test",
+    [("dataname1", data1, "dictionary")],  # List with one tuple (data, type)
+    broker_url="nats://localhost:4222",
+    fileserver_upload_handler=plik_oneshot_upload
+)
 
-# Multiple payloads in one message (each payload has its own type)
-smartsend("/test", [(dataname1, data1, "dictionary"), (dataname2, data2, "table")], ...)
+# Multiple payloads in one message with different types
+smartsend(
+    "/test",
+    [("dataname1", data1, "dictionary"), ("dataname2", data2, "table")],
+    broker_url="nats://localhost:4222",
+    fileserver_upload_handler=plik_oneshot_upload
+)
+
+# Mixed content (e.g., chat with text, image, audio)
+smartsend(
+    "/chat",
+    [
+        ("message_text", "Hello!", "text"),
+        ("user_image", image_data, "image"),
+        ("audio_clip", audio_data, "audio")
+    ],
+    broker_url="nats://localhost:4222"
+)
 
 # Receive returns a dictionary envelope with all metadata and deserialized payloads
-envelope = smartreceive(msg, ...)
-# envelope["payloads"] = [(dataname1, data1, "text"), (dataname2, data2, "table"), ...]
-# envelope["correlationId"], envelope["msgId"], etc.
+env = smartreceive(msg; fileserver_download_handler=_fetch_with_backoff, max_retries=5, base_delay=100, max_delay=5000)
+# env["payloads"] = [("dataname1", data1, type1), ("dataname2", data2, type2), ...]
+# env["correlation_id"], env["msg_id"], etc.
+# env is a dictionary containing envelope metadata and payloads field
 ```
 
 ## Cross-Platform Interoperability
@@ -98,14 +151,14 @@ NATSBridge is designed for seamless communication between Julia, JavaScript, and
 # Julia sender
 using NATSBridge
 data = [("message", "Hello from Julia!", "text")]
-smartsend("/cross_platform", data, nats_url="nats://localhost:4222")
+smartsend("/cross_platform", data, broker_url="nats://localhost:4222")
 ```
 
 ```javascript
 // JavaScript receiver
 const { smartreceive } = require('./src/NATSBridge');
-const envelope = await smartreceive(msg);
-// envelope.payloads[0].data === "Hello from Julia!"
+const env = await smartreceive(msg);
+// env.payloads[0].data === "Hello from Julia!"
 ```
 
 ```python
@@ -146,15 +199,31 @@ All three implementations (Julia, JavaScript, Python/Micropython) follow the sam
       └─────────────────┘                 └─────────────────┘
 ```
 
-## Files
+## smartsend Return Value
+
+The `smartsend` function now returns a tuple containing both the envelope object and the JSON string representation:
+
+```julia
+env, env_json_str = smartsend(...)
+# env::msg_envelope_v1    - The envelope object with all metadata and payloads
+# env_json_str::String    - JSON string for publishing to NATS
+```
+
+**Options:**
+- `is_publish::Bool = true` - When `true` (default), the message is automatically published to NATS. When `false`, the function returns the envelope and JSON string without publishing, allowing manual publishing via NATS request-reply pattern.
+
+This enables two use cases:
+1. **Programmatic envelope access**: Access envelope fields directly via the `env` object
+2. **Direct JSON publishing**: Publish the JSON string directly using NATS request-reply pattern
 
 ### Julia Module: [`src/NATSBridge.jl`](../src/NATSBridge.jl)
 
 The Julia implementation provides:
 
-- **[`MessageEnvelope`](src/NATSBridge.jl)**: Struct for the unified JSON envelope
-- **[`SmartSend()`](src/NATSBridge.jl)**: Handles transport selection based on payload size
-- **[`SmartReceive()`](src/NATSBridge.jl)**: Handles both direct and link transport
+- **[`msg_envelope_v1`](src/NATSBridge.jl)**: Struct for the unified JSON envelope
+- **[`msg_payload_v1`](src/NATSBridge.jl)**: Struct for individual payload representation
+- **[`smartsend()`](src/NATSBridge.jl)**: Handles transport selection based on payload size
+- **[`smartreceive()`](src/NATSBridge.jl)**: Handles both direct and link transport
 
 ### JavaScript Module: [`src/NATSBridge.js`](../src/NATSBridge.js)
 
@@ -247,7 +316,53 @@ node test/scenario3_julia_to_julia.js
 
 ## Usage
 
-### Scenario 0: Basic Multi-Payload Example
+### Scenario 1: Command & Control (Small Dictionary)
+
+**Focus:** Sending small dictionary configurations across platforms. This is the simplest use case for command and control scenarios.
+
+**Julia (Sender/Receiver):**
+```julia
+using NATSBridge
+
+# Subscribe to control subject
+# Parse JSON envelope
+# Execute simulation with parameters
+# Send acknowledgment
+```
+
+**JavaScript (Sender/Receiver):**
+```javascript
+const { smartsend } = require('./src/NATSBridge');
+
+// Create small dictionary config
+// Send via smartsend with type="dictionary"
+const config = {
+    step_size: 0.01,
+    iterations: 1000,
+    threshold: 0.5
+};
+
+await smartsend("control", [
+    { dataname: "config", data: config, type: "dictionary" }
+]);
+```
+
+**Python/Micropython (Sender/Receiver):**
+```python
+from nats_bridge import smartsend
+
+# Create small dictionary config
+# Send via smartsend with type="dictionary"
+config = {
+    "step_size": 0.01,
+    "iterations": 1000,
+    "threshold": 0.5
+}
+
+smartsend("control", [("config", config, "dictionary")])
+```
+
+### Basic Multi-Payload Example
 
 #### Python/Micropython (Sender)
 ```python
@@ -262,16 +377,16 @@ smartsend(
 )
 
 # Even single payload must be wrapped in a list with type
-smartsend("/test", [("single_data", mydata, "dictionary")])
+smartsend("/test", [("single_data", mydata, "dictionary")], nats_url="nats://localhost:4222")
 ```
 
 #### Python/Micropython (Receiver)
 ```python
 from nats_bridge import smartreceive
 
-# Receive returns a list of (dataname, data, type) tuples
-payloads = smartreceive(msg)
-# payloads = [(dataname1, data1, "dictionary"), (dataname2, data2, "table"), ...]
+# Receive returns a dictionary with envelope metadata and payloads field
+env = smartreceive(msg)
+# env["payloads"] = [(dataname1, data1, "dictionary"), (dataname2, data2, "table"), ...]
 ```
 
 #### JavaScript (Sender)
@@ -315,18 +430,18 @@ const nc = await connect({ servers: ['nats://localhost:4222'] });
 const sub = nc.subscribe("control");
 
 for await (const msg of sub) {
-    const envelope = await smartreceive(msg);
+    const env = await smartreceive(msg);
     
     // Process the payloads from the envelope
-    for (const payload of envelope.payloads) {
+    for (const payload of env.payloads) {
         const { dataname, data, type } = payload;
         console.log(`Received ${dataname} of type ${type}`);
         console.log(`Data: ${JSON.stringify(data)}`);
     }
     
     // Also access envelope metadata
-    console.log(`Correlation ID: ${envelope.correlationId}`);
-    console.log(`Message ID: ${envelope.msgId}`);
+    console.log(`Correlation ID: ${env.correlation_id}`);
+    console.log(`Message ID: ${env.msg_id}`);
 }
 ```
 
@@ -344,19 +459,21 @@ df = DataFrame(
     category = rand(["A", "B", "C"], 10_000_000)
 )
 
-# Send via SmartSend - wrapped in a list (type is part of each tuple)
-await SmartSend("analysis_results", [("table_data", df, "table")]);
+# Send via smartsend - wrapped in a list (type is part of each tuple)
+env, env_json_str = smartsend("analysis_results", [("table_data", df, "table")], broker_url="nats://localhost:4222")
+# env: msg_envelope_v1 object with all metadata and payloads
+# env_json_str: JSON string representation of the envelope for publishing
 ```
 
 #### JavaScript (Receiver)
 ```javascript
 const { smartreceive } = require('./src/NATSBridge');
 
-const envelope = await smartreceive(msg);
+const env = await smartreceive(msg);
 
 // Use table data from the payloads field
 // Note: Tables are sent as arrays of objects in JavaScript
-const table = envelope.payloads;
+const table = env.payloads;
 ```
 
 ### Scenario 3: Live Binary Processing
@@ -406,10 +523,10 @@ from nats_bridge import smartreceive
 
 # Receive binary data
 def process_binary(msg):
-    envelope = smartreceive(msg)
+    env = smartreceive(msg)
     
-    # Process the binary data from envelope.payloads
-    for dataname, data, type in envelope["payloads"]:
+    # Process the binary data from env.payloads
+    for dataname, data, type in env["payloads"]:
         if type == "binary":
             # data is bytes
             print(f"Received binary data: {dataname}, size: {len(data)}")
@@ -422,10 +539,10 @@ const { smartreceive } = require('./src/NATSBridge');
 
 // Receive binary data
 function process_binary(msg) {
-    const envelope = await smartreceive(msg);
+    const env = await smartreceive(msg);
     
-    // Process the binary data from envelope.payloads
-    for (const payload of envelope.payloads) {
+    // Process the binary data from env.payloads
+    for (const payload of env.payloads) {
         if (payload.type === "binary") {
             // data is an ArrayBuffer or Uint8Array
             console.log(`Received binary data: ${payload.dataname}, size: ${payload.data.length}`);
@@ -444,7 +561,7 @@ using NATSBridge
 function publish_health_status(nats_url)
     # Send status wrapped in a list (type is part of each tuple)
     status = Dict("cpu" => rand(), "memory" => rand())
-    smartsend("health", [("status", status, "dictionary")], nats_url=nats_url)
+    smartsend("health", [("status", status, "dictionary")], broker_url=nats_url)
     sleep(5)  # Every 5 seconds
 end
 ```
@@ -466,8 +583,8 @@ const consumer = await js.pullSubscribe("health", {
 
 // Process historical and real-time messages
 for await (const msg of consumer) {
-    const envelope = await smartreceive(msg);
-    // envelope.payloads contains the list of payloads
+    const env = await smartreceive(msg);
+    // env.payloads contains the list of payloads
     // Each payload has: dataname, data, type
     msg.ack();
 }
@@ -484,10 +601,10 @@ import json
 
 # Device configuration handler
 def handle_device_config(msg):
-    envelope = smartreceive(msg)
+    env = smartreceive(msg)
     
     # Process configuration from payloads
-    for dataname, data, type in envelope["payloads"]:
+    for dataname, data, type in env["payloads"]:
         if type == "dictionary":
             print(f"Received configuration: {data}")
             # Apply configuration to device
@@ -506,7 +623,7 @@ def handle_device_config(msg):
         "device/response",
         [("config", config, "dictionary")],
         nats_url="nats://localhost:4222",
-        reply_to=envelope.get("replyTo")
+        reply_to=env.get("reply_to")
     )
 ```
 
@@ -566,11 +683,11 @@ smartsend(
 const { smartreceive, smartsend } = require('./src/NATSBridge');
 
 // Receive NATS message with direct transport
-const envelope = await smartreceive(msg);
+const env = await smartreceive(msg);
 
 // Decode Base64 payload (for direct transport)
-// For tables, data is in envelope.payloads
-const table = envelope.payloads;  // Array of objects
+// For tables, data is in env.payloads
+const table = env.payloads;  // Array of objects
 
 // User makes selection
 const selection = uiComponent.getSelectedOption();
@@ -619,7 +736,7 @@ chat_message = [
 smartsend(
     "chat.room123",
     chat_message,
-    nats_url="nats://localhost:4222",
+    broker_url="nats://localhost:4222",
     msg_purpose="chat",
     reply_to="chat.room123.responses"
 )
@@ -667,7 +784,7 @@ await smartsend("chat.room123", message);
 
 **Use Case:** Full-featured chat system supporting rich media. User can send text, small images directly, or upload large files that get uploaded to HTTP server and referenced via URLs. Claim-check pattern ensures reliable delivery tracking for all message components.
 
-**Implementation Note:** The `smartreceive` function iterates through all payloads in the envelope and processes each according to its transport type. See the standard API format in Section 1: `msgEnvelope_v1` supports `AbstractArray{msgPayload_v1}` for multiple payloads.
+**Implementation Note:** The `smartreceive` function iterates through all payloads in the envelope and processes each according to its transport type. See the standard API format in Section 1: `msg_envelope_v1` supports `Vector{msg_payload_v1}` for multiple payloads.
 
 ## Configuration
 
@@ -683,19 +800,19 @@ await smartsend("chat.room123", message);
 
 ```json
 {
-  "correlationId": "uuid-v4-string",
-  "msgId": "uuid-v4-string",
+  "correlation_id": "uuid-v4-string",
+  "msg_id": "uuid-v4-string",
   "timestamp": "2024-01-15T10:30:00Z",
   
-  "sendTo": "topic/subject",
-  "msgPurpose": "ACK | NACK | updateStatus | shutdown | chat",
-  "senderName": "agent-wine-web-frontend",
-  "senderId": "uuid4",
-  "receiverName": "agent-backend",
-  "receiverId": "uuid4",
-  "replyTo": "topic",
-  "replyToMsgId": "uuid4",
-  "BrokerURL": "nats://localhost:4222",
+  "send_to": "topic/subject",
+  "msg_purpose": "ACK | NACK | updateStatus | shutdown | chat",
+  "sender_name": "agent-wine-web-frontend",
+  "sender_id": "uuid4",
+  "receiver_name": "agent-backend",
+  "receiver_id": "uuid4",
+  "reply_to": "topic",
+  "reply_to_msg_id": "uuid4",
+  "broker_url": "nats://localhost:4222",
   
   "metadata": {
     "content_type": "application/octet-stream",
@@ -706,7 +823,7 @@ await smartsend("chat.room123", message);
     {
       "id": "uuid4",
       "dataname": "login_image",
-      "type": "image",
+      "payload_type": "image",
       "transport": "direct",
       "encoding": "base64",
       "size": 15433,

examples/tutorial.md

@@ -107,10 +107,15 @@ python3 -m http.server 8080 --directory /tmp/fileserver
 ```python
 from nats_bridge import smartsend
 
-# Send a text message
+# Send a text message (is_publish=True by default)
 data = [("message", "Hello World", "text")]
-env = smartsend("/chat/room1", data, nats_url="nats://localhost:4222")
+env, env_json_str = smartsend("/chat/room1", data, nats_url="nats://localhost:4222")
 print("Message sent!")
+
+# Or use is_publish=False to get envelope and JSON without publishing
+env, env_json_str = smartsend("/chat/room1", data, nats_url="nats://localhost:4222", is_publish=False)
+# env: MessageEnvelope object
+# env_json_str: JSON string for publishing to NATS
 ```
 
 #### JavaScript
@@ -118,12 +123,19 @@ print("Message sent!")
 ```javascript
 const { smartsend } = require('./src/NATSBridge');
 
-// Send a text message
+// Send a text message (isPublish=true by default)
 await smartsend("/chat/room1", [
     { dataname: "message", data: "Hello World", type: "text" }
 ], { natsUrl: "nats://localhost:4222" });
 
 console.log("Message sent!");
+
+// Or use isPublish=false to get envelope and JSON without publishing
+const { env, env_json_str } = await smartsend("/chat/room1", [
+    { dataname: "message", data: "Hello World", type: "text" }
+], { natsUrl: "nats://localhost:4222", isPublish: false });
+// env: MessageEnvelope object
+// env_json_str: JSON string for publishing to NATS
 ```
 
 #### Julia
@@ -133,7 +145,9 @@ using NATSBridge
 
 # Send a text message
 data = [("message", "Hello World", "text")]
-env = smartsend("/chat/room1", data, nats_url="nats://localhost:4222")
+env, env_json_str = smartsend("/chat/room1", data, nats_url="nats://localhost:4222")
+# env: msgEnvelope_v1 object with all metadata and payloads
+# env_json_str: JSON string representation of the envelope for publishing
 println("Message sent!")
 ```
 
@@ -145,8 +159,8 @@ println("Message sent!")
 from nats_bridge import smartreceive
 
 # Receive and process message
-envelope = smartreceive(msg)
-for dataname, data, type in envelope["payloads"]:
+env = smartreceive(msg)
+for dataname, data, type in env["payloads"]:
     print(f"Received {dataname}: {data}")
 ```
 
@@ -156,8 +170,8 @@ for dataname, data, type in envelope["payloads"]:
 const { smartreceive } = require('./src/NATSBridge');
 
 // Receive and process message
-const envelope = await smartreceive(msg);
-for (const payload of envelope.payloads) {
+const env = await smartreceive(msg);
+for (const payload of env.payloads) {
     console.log(`Received ${payload.dataname}: ${payload.data}`);
 }
 ```
@@ -168,8 +182,8 @@ for (const payload of envelope.payloads) {
 using NATSBridge
 
 # Receive and process message
-envelope = smartreceive(msg, fileserverDownloadHandler)
-for (dataname, data, type) in envelope["payloads"]
+env = smartreceive(msg; fileserver_download_handler=_fetch_with_backoff)
+for (dataname, data, type) in env["payloads"]
     println("Received $dataname: $data")
 end
 ```
@@ -194,7 +208,7 @@ config = {
 
 # Send as dictionary type
 data = [("config", config, "dictionary")]
-env = smartsend("/device/config", data, nats_url="nats://localhost:4222")
+env, env_json_str = smartsend("/device/config", data, nats_url="nats://localhost:4222")
 ```
 
 #### JavaScript
@@ -208,7 +222,7 @@ const config = {
     update_interval: 60
 };
 
-await smartsend("/device/config", [
+const { env, env_json_str } = await smartsend("/device/config", [
     { dataname: "config", data: config, type: "dictionary" }
 ]);
 ```
@@ -225,7 +239,7 @@ config = Dict(
 )
 
 data = [("config", config, "dictionary")]
-smartsend("/device/config", data)
+env, env_json_str = smartsend("/device/config", data)
 ```
 
 ### Example 2: Sending Binary Data (Image)
@@ -241,7 +255,7 @@ with open("image.png", "rb") as f:
 
 # Send as binary type
 data = [("user_image", image_data, "binary")]
-env = smartsend("/chat/image", data, nats_url="nats://localhost:4222")
+env, env_json_str = smartsend("/chat/image", data, nats_url="nats://localhost:4222")
 ```
 
 #### JavaScript
@@ -253,7 +267,7 @@ const { smartsend } = require('./src/NATSBridge');
 const fs = require('fs');
 const image_data = fs.readFileSync('image.png');
 
-await smartsend("/chat/image", [
+const { env, env_json_str } = await smartsend("/chat/image", [
     { dataname: "user_image", data: image_data, type: "binary" }
 ]);
 ```
@@ -267,7 +281,7 @@ using NATSBridge
 image_data = read("image.png")
 
 data = [("user_image", image_data, "binary")]
-smartsend("/chat/image", data)
+env, env_json_str = smartsend("/chat/image", data)
 ```
 
 ### Example 3: Request-Response Pattern
@@ -279,13 +293,15 @@ from nats_bridge import smartsend
 
 # Send command with reply-to
 data = [("command", {"action": "read_sensor"}, "dictionary")]
-env = smartsend(
+env, env_json_str = smartsend(
     "/device/command",
     data,
     nats_url="nats://localhost:4222",
     reply_to="/device/response",
     reply_to_msg_id="cmd-001"
 )
+# env: msgEnvelope_v1 object
+# env_json_str: JSON string for publishing to NATS
 ```
 
 #### JavaScript (Responder)
@@ -297,10 +313,10 @@ const { smartreceive, smartsend } = require('./src/NATSBridge');
 const sub = nc.subscribe("/device/command");
 
 for await (const msg of sub) {
-    const envelope = await smartreceive(msg);
+    const env = await smartreceive(msg);
     
     // Process command
-    for (const payload of envelope.payloads) {
+    for (const payload of env.payloads) {
         if (payload.dataname === "command") {
             const command = payload.data;
             
@@ -315,8 +331,8 @@ for await (const msg of sub) {
                 await smartsend("/device/response", [
                     { dataname: "sensor_data", data: response, type: "dictionary" }
                 ], {
-                    reply_to: envelope.replyTo,
-                    reply_to_msg_id: envelope.msgId
+                    reply_to: env.replyTo,
+                    reply_to_msg_id: env.msgId
                 });
             }
         }
@@ -342,7 +358,7 @@ import os
 large_data = os.urandom(2_000_000)  # 2MB of random data
 
 # Send with file server URL
-env = smartsend(
+env, env_json_str = smartsend(
     "/data/large",
     [("large_file", large_data, "binary")],
     nats_url="nats://localhost:4222",
@@ -364,7 +380,7 @@ const largeData = new ArrayBuffer(2_000_000);
 const view = new Uint8Array(largeData);
 view.fill(42);  // Fill with some data
 
-await smartsend("/data/large", [
+const { env, env_json_str } = await smartsend("/data/large", [
     { dataname: "large_file", data: largeData, type: "binary" }
 ], {
     fileserverUrl: "http://localhost:8080",
@@ -380,7 +396,7 @@ using NATSBridge
 # Create large data (> 1MB)
 large_data = rand(UInt8, 2_000_000)
 
-env = smartsend(
+env, env_json_str = smartsend(
     "/data/large",
     [("large_file", large_data, "binary")],
     fileserver_url="http://localhost:8080"
@@ -409,7 +425,7 @@ data = [
     ("user_avatar", image_data, "image")
 ]
 
-env = smartsend("/chat/mixed", data, nats_url="nats://localhost:4222")
+env, env_json_str = smartsend("/chat/mixed", data, nats_url="nats://localhost:4222")
 ```
 
 #### JavaScript
@@ -419,7 +435,7 @@ const { smartsend } = require('./src/NATSBridge');
 
 const fs = require('fs');
 
-await smartsend("/chat/mixed", [
+const { env, env_json_str } = await smartsend("/chat/mixed", [
     {
         dataname: "message_text",
         data: "Hello with image!",
@@ -445,7 +461,7 @@ data = [
     ("user_avatar", image_data, "image")
 ]
 
-smartsend("/chat/mixed", data)
+env, env_json_str = smartsend("/chat/mixed", data)
 ```
 
 ### Example 6: Table Data (Arrow IPC)
@@ -467,7 +483,7 @@ df = pd.DataFrame({
 
 # Send as table type
 data = [("students", df, "table")]
-env = smartsend("/data/students", data, nats_url="nats://localhost:4222")
+env, env_json_str = smartsend("/data/students", data, nats_url="nats://localhost:4222")
 ```
 
 #### Julia
@@ -484,7 +500,7 @@ df = DataFrame(
 )
 
 data = [("students", df, "table")]
-smartsend("/data/students", data)
+env, env_json_str = smartsend("/data/students", data)
 ```
 
 ---
@@ -503,7 +519,7 @@ using NATSBridge
 # Send dictionary from Julia to JavaScript
 config = Dict("step_size" => 0.01, "iterations" => 1000)
 data = [("config", config, "dictionary")]
-smartsend("/analysis/config", data, nats_url="nats://localhost:4222")
+env, env_json_str = smartsend("/analysis/config", data, nats_url="nats://localhost:4222")
 ```
 
 #### JavaScript Receiver
@@ -512,8 +528,8 @@ smartsend("/analysis/config", data, nats_url="nats://localhost:4222")
 const { smartreceive } = require('./src/NATSBridge');
 
 // Receive dictionary from Julia
-const envelope = await smartreceive(msg);
-for (const payload of envelope.payloads) {
+const env = await smartreceive(msg);
+for (const payload of env.payloads) {
     if (payload.type === "dictionary") {
         console.log("Received config:", payload.data);
         // payload.data = { step_size: 0.01, iterations: 1000 }
@@ -528,7 +544,7 @@ for (const payload of envelope.payloads) {
 ```javascript
 const { smartsend } = require('./src/NATSBridge');
 
-await smartsend("/data/transfer", [
+const { env, env_json_str } = await smartsend("/data/transfer", [
     { dataname: "message", data: "Hello from JS!", type: "text" }
 ]);
 ```
@@ -538,8 +554,8 @@ await smartsend("/data/transfer", [
 ```python
 from nats_bridge import smartreceive
 
-envelope = smartreceive(msg)
-for dataname, data, type in envelope["payloads"]:
+env = smartreceive(msg)
+for dataname, data, type in env["payloads"]:
     if type == "text":
         print(f"Received from JS: {data}")
 ```
@@ -552,7 +568,7 @@ for dataname, data, type in envelope["payloads"]:
 from nats_bridge import smartsend
 
 data = [("message", "Hello from Python!", "text")]
-smartsend("/chat/python", data)
+env, env_json_str = smartsend("/chat/python", data)
 ```
 
 #### Julia Receiver
@@ -560,8 +576,8 @@ smartsend("/chat/python", data)
 ```julia
 using NATSBridge
 
-envelope = smartreceive(msg, fileserverDownloadHandler)
-for (dataname, data, type) in envelope["payloads"]
+env = smartreceive(msg, fileserverDownloadHandler)
+for (dataname, data, type) in env["payloads"]
     if type == "text"
         println("Received from Python: $data")
     end

examples/walkthrough.md

@@ -132,7 +132,7 @@ class ChatUI {
             });
         }
         
-        await smartsend(
+        const { env, env_json_str } = await smartsend(
             `/chat/${this.currentRoom}`,
             data,
             {
@@ -216,15 +216,15 @@ class ChatHandler {
     }
     
     async handleMessage(msg) {
-        const envelope = await smartreceive(msg, {
+        const env = await smartreceive(msg, {
             fileserverDownloadHandler: this.downloadFile.bind(this)
         });
         
         // Extract sender info from envelope
-        const sender = envelope.senderName || 'Anonymous';
+        const sender = env.senderName || 'Anonymous';
         
         // Process each payload
-        for (const payload of envelope.payloads) {
+        for (const payload of env.payloads) {
             if (payload.type === 'text') {
                 this.ui.addMessage(sender, payload.data);
             } else if (payload.type === 'image') {
@@ -304,7 +304,7 @@ class FileUploadService {
             type: 'binary'
         }];
         
-        const envelope = await smartsend(
+        const { env, env_json_str } = await smartsend(
             `/files/${recipient}`,
             data,
             {
@@ -314,7 +314,7 @@ class FileUploadService {
             }
         );
         
-        return envelope;
+        return env;
     }
     
     async uploadLargeFile(filePath, recipient) {
@@ -356,12 +356,12 @@ class FileDownloadService {
     
     async downloadFile(sender, downloadId) {
         // Subscribe to sender's file channel
-        const envelope = await smartreceive(msg, {
+        const env = await smartreceive(msg, {
             fileserverDownloadHandler: this.fetchFromUrl.bind(this)
         });
         
         // Process each payload
-        for (const payload of envelope.payloads) {
+        for (const payload of env.payloads) {
             if (payload.type === 'binary') {
                 const filePath = `/downloads/${payload.dataname}`;
                 fs.writeFileSync(filePath, payload.data);
@@ -422,9 +422,9 @@ async function uploadFile(config) {
     const fileService = new FileUploadService(config.nats_url, config.fileserver_url);
     
     try {
-        const envelope = await fileService.uploadFile(filePath, recipient);
+        const env = await fileService.uploadFile(filePath, recipient);
         console.log('Upload successful!');
-        console.log(`File ID: ${envelope.payloads[0].id}`);
+        console.log(`File ID: ${env.payloads[0].id}`);
     } catch (error) {
         console.error('Upload failed:', error.message);
     }
@@ -514,6 +514,7 @@ class SensorSender:
         
         data = [("reading", reading.to_dict(), "dictionary")]
         
+        # Default: is_publish=True (automatically publishes to NATS)
         smartsend(
             f"/sensors/{sensor_id}",
             data,
@@ -521,6 +522,31 @@ class SensorSender:
             fileserver_url=self.fileserver_url
         )
         
+    def prepare_message_only(self, sensor_id: str, value: float, unit: str):
+        """Prepare a message without publishing (is_publish=False)."""
+        reading = SensorReading(
+            sensor_id=sensor_id,
+            timestamp=datetime.now().isoformat(),
+            value=value,
+            unit=unit
+        )
+        
+        data = [("reading", reading.to_dict(), "dictionary")]
+        
+        # With is_publish=False, returns (env, env_json_str) without publishing
+        env, env_json_str = smartsend(
+            f"/sensors/{sensor_id}/prepare",
+            data,
+            nats_url=self.nats_url,
+            fileserver_url=self.fileserver_url,
+            is_publish=False
+        )
+        
+        # Now you can publish manually using NATS request-reply pattern
+        # nc.request(subject, env_json_str, reply_to=reply_to_topic)
+        
+        return env, env_json_str
+        
     def send_batch(self, readings: List[SensorReading]):
         batch = SensorBatch()
         for reading in readings:
@@ -571,9 +597,9 @@ class SensorReceiver:
         self.fileserver_download_handler = fileserver_download_handler
         
     def process_reading(self, msg):
-        envelope = smartreceive(msg, self.fileserver_download_handler)
+        env = smartreceive(msg, self.fileserver_download_handler)
         
-        for dataname, data, data_type in envelope["payloads"]:
+        for dataname, data, data_type in env["payloads"]:
             if data_type == "dictionary":
                 reading = SensorReading(
                     sensor_id=data["sensor_id"],
@@ -673,10 +699,10 @@ class DeviceBridge:
             # Poll for messages
             msg = self._poll_for_message()
             if msg:
-                envelope = smartreceive(msg)
+                env = smartreceive(msg)
                 
                 # Process payloads
-                for dataname, data, data_type in envelope["payloads"]:
+                for dataname, data, data_type in env["payloads"]:
                     if dataname == "command":
                         callback(data)
                         
@@ -772,9 +798,9 @@ class DashboardServer:
         
     def receive_selection(self, callback):
         def handler(msg):
-            envelope = smartreceive(msg)
+            env = smartreceive(msg)
             
-            for dataname, data, data_type in envelope["payloads"]:
+            for dataname, data, data_type in env["payloads"]:
                 if data_type == "dictionary":
                     callback(data)
                     
@@ -807,7 +833,7 @@ class DashboardUI {
     
     async refreshData() {
         // Request fresh data
-        await smartsend("/dashboard/request", [
+        const { env, env_json_str } = await smartsend("/dashboard/request", [
             { dataname: "request", data: { type: "refresh" }, type: "dictionary" }
         ], {
             fileserverUrl: window.config.fileserver_url
@@ -816,12 +842,12 @@ class DashboardUI {
     
     async fetchData() {
         // Subscribe to data updates
-        const envelope = await smartreceive(msg, {
+        const env = await smartreceive(msg, {
             fileserverDownloadHandler: this.fetchFromUrl.bind(this)
         });
         
         // Process table data
-        for (const payload of envelope.payloads) {
+        for (const payload of env.payloads) {
             if (payload.type === 'table') {
                 // Deserialize Arrow IPC
                 this.data = this.deserializeArrow(payload.data);

plik_fileserver/docker-compose.yml

@@ -0,0 +1,14 @@
+services:
+  plik:
+    image: rootgg/plik:latest
+    container_name: plik-server
+    restart: unless-stopped
+    ports:
+      - "8080:8080"
+    volumes:
+      # # Mount the config file (created below)
+      # - ./plikd.cfg:/home/plik/server/plikd.cfg
+      # Mount local folder for uploads and database
+      - ./plik-data:/data
+    # Set user to match your host UID to avoid permission issues
+    user: "1000:1000"

src/NATSBridge.js

@@ -460,8 +460,9 @@ async function smartsend(subject, data, options = {}) {
      * @param {string} options.receiverId - UUID of the receiver (default: "")
      * @param {string} options.replyTo - Topic to reply to (default: "")
      * @param {string} options.replyToMsgId - Message ID this message is replying to (default: "")
+     * @param {boolean} options.isPublish - Whether to automatically publish the message to NATS (default: true)
      * 
-     * @returns {Promise<MessageEnvelope>} - The envelope for tracking
+     * @returns {Promise<Object>} - An object with { env: MessageEnvelope, env_json_str: string }
      */
     const {
         natsUrl = DEFAULT_NATS_URL,
@@ -474,7 +475,8 @@ async function smartsend(subject, data, options = {}) {
         receiverName = "",
         receiverId = "",
         replyTo = "",
-        replyToMsgId = ""
+        replyToMsgId = "",
+        isPublish = true  // Whether to automatically publish the message to NATS
     } = options;
     
     log_trace(correlationId, `Starting smartsend for subject: ${subject}`);
@@ -556,10 +558,19 @@ async function smartsend(subject, data, options = {}) {
         payloads: payloads
     });
     
-    // Publish message to NATS
-    await publish_message(natsUrl, subject, env.toString(), correlationId);
+    // Convert envelope to JSON string
+    const env_json_str = env.toString();
     
-    return env;
+    // Publish to NATS if isPublish is true
+    if (isPublish) {
+        await publish_message(natsUrl, subject, env_json_str, correlationId);
+    }
+    
+    // Return both envelope and JSON string (tuple-like structure)
+    return {
+        env: env,
+        env_json_str: env_json_str
+    };
 }
 
 // Helper: Publish message to NATS

src/README.md

@@ -1,295 +0,0 @@
-# NATSBridge
-
-A high-performance, bi-directional data bridge for **Julia**, **JavaScript**, and **Python/Micropython** using NATS (Core & JetStream), implementing the Claim-Check pattern for large payloads.
-
-## Overview
-
-NATSBridge enables seamless communication between Julia, JavaScript, and Python/Micropython applications through NATS, with automatic transport selection based on payload size:
-
-- **Direct Transport**: Payloads < 1MB are sent directly via NATS (Base64 encoded)
-- **Link Transport**: Payloads >= 1MB are uploaded to an HTTP file server and referenced via URL
-
-## Features
-
-- ✅ Bi-directional NATS communication across Julia ↔ JavaScript ↔ Python/Micropython
-- ✅ Multi-payload support (mixed content in single message)
-- ✅ Automatic transport selection based on payload size
-- ✅ File server integration for large payloads
-- ✅ Exponential backoff for URL fetching
-- ✅ Correlation ID tracking
-- ✅ Reply-to support for request-response pattern
-
-## Supported Payload Types
-
-| Type | Description |
-|------|-------------|
-| `text` | Plain text strings |
-| `dictionary` | JSON-serializable dictionaries |
-| `table` | Tabular data (Arrow IPC format) |
-| `image` | Image data (PNG, JPG bytes) |
-| `audio` | Audio data (WAV, MP3 bytes) |
-| `video` | Video data (MP4, AVI bytes) |
-| `binary` | Generic binary data |
-
-## Implementation Guides
-
-### [Julia Implementation](../tutorial_julia.md)
-
-See the [Julia tutorial](../tutorial_julia.md) for getting started with Julia.
-
-### [JavaScript Implementation](#javascript-implementation)
-
-See [`NATSBridge.js`](NATSBridge.js) for the JavaScript implementation.
-
-### [Python/Micropython Implementation](#pythonmicropython-implementation)
-
-See [`nats_bridge.py`](nats_bridge.py) for the Python/Micropython implementation.
-
-## Installation
-
-### Julia
-
-```julia
-using Pkg
-Pkg.add("NATS")
-Pkg.add("Arrow")
-Pkg.add("JSON3")
-Pkg.add("HTTP")
-Pkg.add("UUIDs")
-Pkg.add("Dates")
-```
-
-### JavaScript
-
-```bash
-npm install nats.js apache-arrow uuid base64-url
-```
-
-### Python/Micropython
-
-1. Copy `nats_bridge.py` to your device
-2. Ensure you have the following dependencies:
-   - `urequests` for HTTP requests (Micropython)
-   - `requests` for HTTP requests (Python)
-   - `base64` for base64 encoding
-   - `json` for JSON handling
-   - `socket` for networking (Micropython)
-
-## Usage
-
-### Basic Text Message
-
-#### Python/Micropython
-
-```python
-from nats_bridge import smartsend, smartreceive
-
-# Sender
-data = [("message", "Hello World", "text")]
-env = smartsend("/chat/room1", data, nats_url="nats://localhost:4222")
-
-# Receiver
-payloads = smartreceive(msg)
-for dataname, data, type in payloads:
-    print("Received {}: {}".format(dataname, data))
-```
-
-#### Julia
-
-```julia
-using NATSBridge
-
-# Sender
-data = [("message", "Hello World", "text")]
-env = smartsend("/chat/room1", data, nats_url="nats://localhost:4222")
-
-# Receiver
-envelope = smartreceive(msg, fileserverDownloadHandler)
-# envelope["payloads"] = [("message", "Hello World", "text"), ...]
-```
-
-#### JavaScript
-
-```javascript
-const { smartsend, smartreceive } = require('./src/NATSBridge');
-
-// Sender
-await smartsend("/chat/room1", [
-    { dataname: "message", data: "Hello World", type: "text" }
-], { natsUrl: "nats://localhost:4222" });
-
-// Receiver
-const envelope = await smartreceive(msg);
-// envelope.payloads = [{ dataname: "message", data: "Hello World", type: "text" }, ...]
-```
-
-### Sending JSON Configuration
-
-#### Python/Micropython
-
-```python
-from nats_bridge import smartsend
-
-config = {
-    "wifi_ssid": "MyNetwork",
-    "wifi_password": "password123",
-    "update_interval": 60
-}
-
-data = [("config", config, "dictionary")]
-env = smartsend("/device/config", data, nats_url="nats://localhost:4222")
-```
-
-### Mixed Content (Chat with Text + Image)
-
-#### Python/Micropython
-
-```python
-from nats_bridge import smartsend
-
-image_data = b"\x89PNG..."  # PNG bytes
-
-data = [
-    ("message_text", "Hello with image!", "text"),
-    ("user_avatar", image_data, "binary")
-]
-
-env = smartsend("/chat/mixed", data, nats_url="nats://localhost:4222")
-```
-
-### Request-Response Pattern
-
-#### Python/Micropython
-
-```python
-from nats_bridge import smartsend
-
-# Send command with reply-to
-data = [("command", {"action": "read_sensor"}, "dictionary")]
-env = smartsend(
-    "/device/command",
-    data,
-    nats_url="nats://localhost:4222",
-    reply_to="/device/response",
-    reply_to_msg_id="cmd-001"
-)
-```
-
-### Large Payloads (File Server)
-
-#### Python/Micropython
-
-```python
-from nats_bridge import smartsend
-
-# Large data (> 1MB)
-large_data = b"A" * 2000000  # 2MB
-
-env = smartsend(
-    "/data/large",
-    [("large_file", large_data, "binary")],
-    nats_url="nats://localhost:4222",
-    fileserver_url="http://localhost:8080",
-    size_threshold=1000000  # 1MB threshold
-)
-```
-
-## API Reference
-
-### `smartsend(subject, data, ...)`
-
-Send data via NATS with automatic transport selection.
-
-**Arguments:**
-- `subject` (str): NATS subject to publish to
-- `data` (list): List of `(dataname, data, type)` tuples
-- `nats_url` (str): NATS server URL (default: `nats://localhost:4222`)
-- `fileserver_url` (str): HTTP file server URL (default: `http://localhost:8080`)
-- `size_threshold` (int): Threshold in bytes (default: 1,000,000)
-- `correlation_id` (str): Optional correlation ID for tracing
-- `msg_purpose` (str): Message purpose (default: `"chat"`)
-- `sender_name` (str): Sender name (default: `"NATSBridge"`)
-- `receiver_name` (str): Receiver name (default: `""`)
-- `receiver_id` (str): Receiver ID (default: `""`)
-- `reply_to` (str): Reply topic (default: `""`)
-- `reply_to_msg_id` (str): Reply message ID (default: `""`)
-
-**Returns:** `MessageEnvelope` object
-
-### `smartreceive(msg, ...)`
-
-Receive and process NATS messages.
-
-**Arguments:**
-- `msg`: NATS message (dict or JSON string)
-- `fileserver_download_handler` (function): Function to fetch data from URLs
-- `max_retries` (int): Maximum retry attempts (default: 5)
-- `base_delay` (int): Initial delay in ms (default: 100)
-- `max_delay` (int): Maximum delay in ms (default: 5000)
-
-**Returns:** List of `(dataname, data, type)` tuples
-
-### `MessageEnvelope`
-
-Represents a complete NATS message envelope.
-
-**Attributes:**
-- `correlation_id`: Unique identifier for tracing
-- `msg_id`: Unique message identifier
-- `timestamp`: Message publication timestamp
-- `send_to`: NATS subject
-- `msg_purpose`: Message purpose
-- `sender_name`: Sender name
-- `sender_id`: Sender UUID
-- `receiver_name`: Receiver name
-- `receiver_id`: Receiver UUID
-- `reply_to`: Reply topic
-- `reply_to_msg_id`: Reply message ID
-- `broker_url`: NATS broker URL
-- `metadata`: Message-level metadata
-- `payloads`: List of MessagePayload objects
-
-### `MessagePayload`
-
-Represents a single payload within a message envelope.
-
-**Attributes:**
-- `id`: Unique payload identifier
-- `dataname`: Name of the payload
-- `type`: Payload type ("text", "dictionary", etc.)
-- `transport`: Transport method ("direct" or "link")
-- `encoding`: Encoding method ("none", "base64", etc.)
-- `size`: Payload size in bytes
-- `data`: Payload data (bytes for direct, URL for link)
-- `metadata`: Payload-level metadata
-
-## Examples
-
-See [`examples/micropython_example.py`](../examples/micropython_example.py) for more detailed examples.
-
-## Testing
-
-Run the test suite:
-
-```bash
-# Python/Micropython
-python test/test_micropython_basic.py
-
-# JavaScript
-node test/test_js_to_js_text_sender.js
-node test/test_js_to_js_text_receiver.js
-
-# Julia
-julia test/test_julia_to_julia_text_sender.jl
-julia test/test_julia_to_julia_text_receiver.jl
-```
-
-## Requirements
-
-- **Julia**: NATS server (nats.io), HTTP file server (optional)
-- **JavaScript**: NATS server (nats.io), HTTP file server (optional)
-- **Python/Micropython**: NATS server (nats.io), HTTP file server (optional)
-
-## License
-
-MIT

src/nats_bridge.py

@@ -437,7 +437,7 @@ def plik_oneshot_upload(file_server_url, filename, data):
 def smartsend(subject, data, nats_url=DEFAULT_NATS_URL, fileserver_url=DEFAULT_FILESERVER_URL,
               fileserver_upload_handler=plik_oneshot_upload, size_threshold=DEFAULT_SIZE_THRESHOLD,
               correlation_id=None, msg_purpose="chat", sender_name="NATSBridge",
-              receiver_name="", receiver_id="", reply_to="", reply_to_msg_id=""):
+              receiver_name="", receiver_id="", reply_to="", reply_to_msg_id="", is_publish=True):
     """Send data either directly via NATS or via a fileserver URL, depending on payload size.
     
     This function intelligently routes data delivery based on payload size relative to a threshold.
@@ -459,9 +459,12 @@ def smartsend(subject, data, nats_url=DEFAULT_NATS_URL, fileserver_url=DEFAULT_F
         receiver_id: UUID of the receiver
         reply_to: Topic to reply to
         reply_to_msg_id: Message ID this message is replying to
+        is_publish: Whether to automatically publish the message to NATS (default: True)
     
     Returns:
-        MessageEnvelope: The envelope object for tracking
+        tuple: (env, env_json_str) where:
+            - env: MessageEnvelope object with all metadata and payloads
+            - env_json_str: JSON string representation of the envelope for publishing
     """
     # Generate correlation ID if not provided
     cid = correlation_id if correlation_id else str(uuid.uuid4())
@@ -549,13 +552,15 @@ def smartsend(subject, data, nats_url=DEFAULT_NATS_URL, fileserver_url=DEFAULT_F
     
     msg_json = env.to_json()
     
-    # Publish to NATS
-    nats_conn = NATSConnection(nats_url)
-    nats_conn.connect()
-    nats_conn.publish(subject, msg_json)
-    nats_conn.close()
+    # Publish to NATS if is_publish is True
+    if is_publish:
+        nats_conn = NATSConnection(nats_url)
+        nats_conn.connect()
+        nats_conn.publish(subject, msg_json)
+        nats_conn.close()
     
-    return env
+    # Return tuple of (envelope, json_string) for both direct and link transport
+    return (env, msg_json)
 
 
 def smartreceive(msg, fileserver_download_handler=_fetch_with_backoff, max_retries=5,

test/test_js_dict_sender.js

@@ -118,7 +118,7 @@ async function test_dict_send() {
     // Use smartsend with dictionary type
     // For small Dictionary: will use direct transport (JSON encoded)
     // For large Dictionary: will use link transport (uploaded to fileserver)
-    const env = await smartsend(
+    const { env, env_json_str } = await smartsend(
         SUBJECT,
         [data1, data2],
         {
@@ -132,7 +132,8 @@ async function test_dict_send() {
             receiverName: "",
             receiverId: "",
             replyTo: "",
-            replyToMsgId: ""
+            replyToMsgId: "",
+            isPublish: true  // Publish the message to NATS
         }
     );
     

test/test_js_file_sender.js

@@ -98,7 +98,7 @@ async function test_large_binary_send() {
     
     // Use smartsend with binary type - will automatically use link transport
     // if file size exceeds the threshold (1MB by default)
-    const env = await smartsend(
+    const { env, env_json_str } = await smartsend(
         SUBJECT,
         [data1, data2],
         {
@@ -112,7 +112,8 @@ async function test_large_binary_send() {
             receiverName: "",
             receiverId: "",
             replyTo: "",
-            replyToMsgId: ""
+            replyToMsgId: "",
+            isPublish: true  // Publish the message to NATS
         }
     );
     

test/test_js_mix_payload_sender.js

@@ -222,7 +222,7 @@ async function test_mix_send() {
     ];
     
     // Use smartsend with mixed content
-    const env = await smartsend(
+    const { env, env_json_str } = await smartsend(
         SUBJECT,
         payloads,
         {
@@ -236,7 +236,8 @@ async function test_mix_send() {
             receiverName: "",
             receiverId: "",
             replyTo: "",
-            replyToMsgId: ""
+            replyToMsgId: "",
+            isPublish: true  // Publish the message to NATS
         }
     );
     

test/test_js_table_sender.js

@@ -118,7 +118,7 @@ async function test_table_send() {
     // Use smartsend with table type
     // For small Table: will use direct transport (Arrow IPC encoded)
     // For large Table: will use link transport (uploaded to fileserver)
-    const env = await smartsend(
+    const { env, env_json_str } = await smartsend(
         SUBJECT,
         [data1, data2],
         {
@@ -132,7 +132,8 @@ async function test_table_send() {
             receiverName: "",
             receiverId: "",
             replyTo: "",
-            replyToMsgId: ""
+            replyToMsgId: "",
+            isPublish: true  // Publish the message to NATS
         }
     );
     

test/test_js_text_sender.js

@@ -94,7 +94,7 @@ async function test_text_send() {
     // Use smartsend with text type
     // For small text: will use direct transport (Base64 encoded UTF-8)
     // For large text: will use link transport (uploaded to fileserver)
-    const env = await smartsend(
+    const { env, env_json_str } = await smartsend(
         SUBJECT,
         [data1, data2],
         {
@@ -108,7 +108,8 @@ async function test_text_send() {
             receiverName: "",
             receiverId: "",
             replyTo: "",
-            replyToMsgId: ""
+            replyToMsgId: "",
+            isPublish: true  // Publish the message to NATS
         }
     );
     

test/test_julia_dict_sender.jl

@@ -92,12 +92,12 @@ function test_dict_send()
     # Use smartsend with dictionary type
     # For small Dictionary: will use direct transport (JSON encoded)
     # For large Dictionary: will use link transport (uploaded to fileserver)
-    env = NATSBridge.smartsend(
+    env, env_json_str = NATSBridge.smartsend(
         SUBJECT,
         [data1, data2];  # List of (dataname, data, type) tuples
-        nats_url = NATS_URL,
+        broker_url = NATS_URL,
         fileserver_url = FILESERVER_URL,
-        fileserverUploadHandler = plik_upload_handler,
+        fileserver_upload_handler = plik_upload_handler,
         size_threshold = 1_000_000,  # 1MB threshold
         correlation_id = correlation_id,
         msg_purpose = "chat",
@@ -105,7 +105,8 @@ function test_dict_send()
         receiver_name = "",
         receiver_id = "",
         reply_to = "",
-        reply_to_msg_id = ""
+        reply_to_msg_id = "",
+        is_publish = true  # Publish the message to NATS
     )
     
     log_trace("Sent message with $(length(env.payloads)) payloads")
@@ -114,7 +115,7 @@ function test_dict_send()
     for (i, payload) in enumerate(env.payloads)
         log_trace("Payload $i ('$payload.dataname'):")
         log_trace("  Transport: $(payload.transport)")
-        log_trace("  Type: $(payload.type)")
+        log_trace("  Type: $(payload.payload_type)")
         log_trace("  Size: $(payload.size) bytes")
         log_trace("  Encoding: $(payload.encoding)")
         

test/test_julia_file_sender.jl

@@ -79,12 +79,12 @@ function test_large_binary_send()
     # Use smartsend with binary type - will automatically use link transport
     # if file size exceeds the threshold (1MB by default)
     # API: smartsend(subject, [(dataname, data, type), ...]; keywords...)
-    env = NATSBridge.smartsend(
+    env, env_json_str = NATSBridge.smartsend(
         SUBJECT,
         [data1, data2];  # List of (dataname, data, type) tuples
-        nats_url = NATS_URL;
+        broker_url = NATS_URL;
         fileserver_url = FILESERVER_URL,
-        fileserverUploadHandler = plik_upload_handler,
+        fileserver_upload_handler = plik_upload_handler,
         size_threshold = 1_000_000,
         correlation_id = correlation_id,
         msg_purpose = "chat",
@@ -92,11 +92,12 @@ function test_large_binary_send()
         receiver_name = "",
         receiver_id = "",
         reply_to = "",
-        reply_to_msg_id = ""
+        reply_to_msg_id = "",
+        is_publish = true  # Publish the message to NATS
     )
     
     log_trace("Sent message with transport: $(env.payloads[1].transport)")
-    log_trace("Envelope type: $(env.payloads[1].type)")
+    log_trace("Envelope type: $(env.payloads[1].payload_type)")
     
     # Check if link transport was used
     if env.payloads[1].transport == "link"

test/test_julia_mix_payloads_sender.jl

@@ -186,12 +186,12 @@ function test_mix_send()
     ]
     
     # Use smartsend with mixed content
-    env = NATSBridge.smartsend(
+    env, env_json_str = NATSBridge.smartsend(
         SUBJECT,
         payloads;  # List of (dataname, data, type) tuples
-        nats_url = NATS_URL,
+        broker_url = NATS_URL,
         fileserver_url = FILESERVER_URL,
-        fileserverUploadHandler = plik_upload_handler,
+        fileserver_upload_handler = plik_upload_handler,
         size_threshold = 1_000_000,  # 1MB threshold
         correlation_id = correlation_id,
         msg_purpose = "chat",
@@ -199,7 +199,8 @@ function test_mix_send()
         receiver_name = "",
         receiver_id = "",
         reply_to = "",
-        reply_to_msg_id = ""
+        reply_to_msg_id = "",
+        is_publish = true  # Publish the message to NATS
     )
     
     log_trace("Sent message with $(length(env.payloads)) payloads")
@@ -208,7 +209,7 @@ function test_mix_send()
     for (i, payload) in enumerate(env.payloads)
         log_trace("Payload $i ('$payload.dataname'):")
         log_trace("  Transport: $(payload.transport)")
-        log_trace("  Type: $(payload.type)")
+        log_trace("  Type: $(payload.payload_type)")
         log_trace("  Size: $(payload.size) bytes")
         log_trace("  Encoding: $(payload.encoding)")
         

test/test_julia_table_sender.jl

@@ -90,12 +90,12 @@ function test_table_send()
     # Use smartsend with table type
     # For small DataFrame: will use direct transport (Base64 encoded Arrow IPC)
     # For large DataFrame: will use link transport (uploaded to fileserver)
-    env = NATSBridge.smartsend(
+    env, env_json_str = NATSBridge.smartsend(
         SUBJECT,
         [data1, data2];  # List of (dataname, data, type) tuples
-        nats_url = NATS_URL,
+        broker_url = NATS_URL,
         fileserver_url = FILESERVER_URL,
-        fileserverUploadHandler = plik_upload_handler,
+        fileserver_upload_handler = plik_upload_handler,
         size_threshold = 1_000_000,  # 1MB threshold
         correlation_id = correlation_id,
         msg_purpose = "chat",
@@ -103,7 +103,8 @@ function test_table_send()
         receiver_name = "",
         receiver_id = "",
         reply_to = "",
-        reply_to_msg_id = ""
+        reply_to_msg_id = "",
+        is_publish = true  # Publish the message to NATS
     )
     
     log_trace("Sent message with $(length(env.payloads)) payloads")
@@ -112,7 +113,7 @@ function test_table_send()
     for (i, payload) in enumerate(env.payloads)
         log_trace("Payload $i ('$payload.dataname'):")
         log_trace("  Transport: $(payload.transport)")
-        log_trace("  Type: $(payload.type)")
+        log_trace("  Type: $(payload.payload_type)")
         log_trace("  Size: $(payload.size) bytes")
         log_trace("  Encoding: $(payload.encoding)")
         

test/test_julia_text_sender.jl

@@ -75,12 +75,12 @@ function test_text_send()
     # Use smartsend with text type
     # For small text: will use direct transport (Base64 encoded UTF-8)
     # For large text: will use link transport (uploaded to fileserver)
-    env = NATSBridge.smartsend(
+    env, env_json_str = NATSBridge.smartsend(
         SUBJECT,
         [data1, data2];  # List of (dataname, data, type) tuples
-        nats_url = NATS_URL,
+        broker_url = NATS_URL,
         fileserver_url = FILESERVER_URL,
-        fileserverUploadHandler = plik_upload_handler,
+        fileserver_upload_handler = plik_upload_handler,
         size_threshold = 1_000_000,  # 1MB threshold
         correlation_id = correlation_id,
         msg_purpose = "chat",
@@ -88,7 +88,8 @@ function test_text_send()
         receiver_name = "",
         receiver_id = "",
         reply_to = "",
-        reply_to_msg_id = ""
+        reply_to_msg_id = "",
+        is_publish = true  # Publish the message to NATS
     )
     
     log_trace("Sent message with $(length(env.payloads)) payloads")
@@ -97,7 +98,7 @@ function test_text_send()
     for (i, payload) in enumerate(env.payloads)
         log_trace("Payload $i ('$payload.dataname'):")
         log_trace("  Transport: $(payload.transport)")
-        log_trace("  Type: $(payload.type)")
+        log_trace("  Type: $(payload.payload_type)")
         log_trace("  Size: $(payload.size) bytes")
         log_trace("  Encoding: $(payload.encoding)")
         

test/test_micropython_dict_sender.py

@@ -64,7 +64,7 @@ def main():
     log_trace(correlation_id, f"Correlation ID: {correlation_id}")
     
     # Use smartsend with dictionary type
-    env = smartsend(
+    env, env_json_str = smartsend(
         SUBJECT,
         [data1, data2],  # List of (dataname, data, type) tuples
         nats_url=NATS_URL,
@@ -76,7 +76,8 @@ def main():
         receiver_name="",
         receiver_id="",
         reply_to="",
-        reply_to_msg_id=""
+        reply_to_msg_id="",
+        is_publish=True  # Publish the message to NATS
     )
     
     log_trace(correlation_id, f"Sent message with {len(env.payloads)} payloads")

test/test_micropython_file_sender.py

@@ -44,7 +44,7 @@ def main():
     log_trace(correlation_id, f"Correlation ID: {correlation_id}")
     
     # Use smartsend with binary type
-    env = smartsend(
+    env, env_json_str = smartsend(
         SUBJECT,
         [data1, data2],  # List of (dataname, data, type) tuples
         nats_url=NATS_URL,
@@ -56,7 +56,8 @@ def main():
         receiver_name="",
         receiver_id="",
         reply_to="",
-        reply_to_msg_id=""
+        reply_to_msg_id="",
+        is_publish=True  # Publish the message to NATS
     )
     
     log_trace(correlation_id, f"Sent message with {len(env.payloads)} payloads")

test/test_micropython_mixed_sender.py

@@ -58,7 +58,7 @@ def main():
     log_trace(correlation_id, f"Correlation ID: {correlation_id}")
     
     # Use smartsend with mixed types
-    env = smartsend(
+    env, env_json_str = smartsend(
         SUBJECT,
         data,  # List of (dataname, data, type) tuples
         nats_url=NATS_URL,
@@ -70,7 +70,8 @@ def main():
         receiver_name="",
         receiver_id="",
         reply_to="",
-        reply_to_msg_id=""
+        reply_to_msg_id="",
+        is_publish=True  # Publish the message to NATS
     )
     
     log_trace(correlation_id, f"Sent message with {len(env.payloads)} payloads")

test/test_micropython_text_sender.py

@@ -46,7 +46,7 @@ def main():
     # Use smartsend with text type
     # For small text: will use direct transport (Base64 encoded UTF-8)
     # For large text: will use link transport (uploaded to fileserver)
-    env = smartsend(
+    env, env_json_str = smartsend(
         SUBJECT,
         [data1, data2],  # List of (dataname, data, type) tuples
         nats_url=NATS_URL,
@@ -58,7 +58,8 @@ def main():
         receiver_name="",
         receiver_id="",
         reply_to="",
-        reply_to_msg_id=""
+        reply_to_msg_id="",
+        is_publish=True  # Publish the message to NATS
     )
     
     log_trace(correlation_id, f"Sent message with {len(env.payloads)} payloads")