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NATSBridge.jl Walkthrough: Building a Chat System

A step-by-step guided walkthrough for building a real-time chat system using NATSBridge.jl with mixed content support (text, images, audio, video, and files).

Prerequisites

Julia 1.7+
NATS server running
HTTP file server (Plik) running

Step 1: Understanding the Chat System Architecture

System Components

┌─────────────────────────────────────────────────────────────────────────────┐
│                              Chat System                                   │
├─────────────────────────────────────────────────────────────────────────────┤
│                                                                            │
│  ┌──────────────┐        NATS         ┌──────────────┐                     │
│  │   Julia      │◄───────┬───────►   │   JavaScript │                     │
│  │  Service     │        │          │   Client     │                     │
│  │              │        │          │              │                     │
│  │ - Text       │        │          │ - Text       │                     │
│  │ - Images     │        │          │ - Images     │                     │
│  │ - Audio      │        ▼          │ - Audio      │                     │
│  │ - Video      │  NATSBridge.jl    │ - Files      │                     │
│  │ - Files      │        │          │ - Tables     │                     │
│  └──────────────┘        │          └──────────────┘                     │
│                          │                                                 │
│                  ┌───────┴───────┐                                         │
│                  │   NATS      │                                         │
│                  │   Server    │                                         │
│                  └─────────────┘                                         │
│                                                                            │
└─────────────────────────────────────────────────────────────────────────────┘

For large payloads (> 1MB):
┌─────────────────────────────────────────────────────────────────────────────┐
│                           File Server (Plik)                               │
│                                                                            │
│  Julia Service ──► Upload ──► File Server ──► Download ◄── JavaScript Client│
│                                                                            │
└─────────────────────────────────────────────────────────────────────────────┘

Message Format

Each chat message is an envelope containing multiple payloads:

{
  "correlationId": "uuid4",
  "msgId": "uuid4",
  "timestamp": "2024-01-15T10:30:00Z",
  "sendTo": "/chat/room1",
  "msgPurpose": "chat",
  "senderName": "user-1",
  "senderId": "uuid4",
  "receiverName": "user-2",
  "receiverId": "uuid4",
  "brokerURL": "nats://localhost:4222",
  "payloads": [
    {
      "id": "uuid4",
      "dataname": "message_text",
      "type": "text",
      "transport": "direct",
      "encoding": "base64",
      "size": 256,
      "data": "SGVsbG8gV29ybGQh",
      "metadata": {}
    },
    {
      "id": "uuid4",
      "dataname": "user_image",
      "type": "image",
      "transport": "link",
      "encoding": "none",
      "size": 15433,
      "data": "http://localhost:8080/file/UPLOAD_ID/FILE_ID/image.jpg",
      "metadata": {}
    }
  ]
}

Step 2: Setting Up the Environment

1. Start NATS Server

# Using Docker
docker run -d -p 4222:4222 -p 8222:8222 --name nats-server nats:latest

# Or download from https://github.com/nats-io/nats-server/releases
./nats-server

2. Start HTTP File Server (Plik)

# Using Docker
docker run -d -p 8080:8080 --name plik plik/plik:latest

# Or download from https://github.com/arnaud-lb/plik/releases
./plikd -d

3. Install Julia Dependencies

using Pkg
Pkg.add("NATS")
Pkg.add("JSON")
Pkg.add("Arrow")
Pkg.add("HTTP")
Pkg.add("UUIDs")
Pkg.add("Dates")
Pkg.add("Base64")
Pkg.add("PrettyPrinting")
Pkg.add("DataFrames")

Step 3: Basic Text-Only Chat

Sender (User 1)

using NATS
using JSON
using UUIDs
using Dates
using PrettyPrinting
using DataFrames
using Arrow
using HTTP
using Base64

# Include the bridge module
include("NATSBridge.jl")
using .NATSBridge

# Configuration
const NATS_URL = "nats://localhost:4222"
const FILESERVER_URL = "http://localhost:8080"
const SUBJECT = "/chat/room1"

# File upload handler for plik server
function plik_upload_handler(fileserver_url::String, dataname::String, data::Vector{UInt8})::Dict{String, Any}
    url_getUploadID = "$fileserver_url/upload"
    headers = ["Content-Type" => "application/json"]
    body = """{ "OneShot" : true }"""
    httpResponse = HTTP.request("POST", url_getUploadID, headers, body; body_is_form=false)
    responseJson = JSON.parse(String(httpResponse.body))
    uploadid = responseJson["id"]
    uploadtoken = responseJson["uploadToken"]
    
    file_multipart = HTTP.Multipart(dataname, IOBuffer(data), "application/octet-stream")
    url_upload = "$fileserver_url/file/$uploadid"
    headers = ["X-UploadToken" => uploadtoken]
    
    form = HTTP.Form(Dict("file" => file_multipart))
    httpResponse = HTTP.post(url_upload, headers, form)
    responseJson = JSON.parse(String(httpResponse.body))
    
    fileid = responseJson["id"]
    url = "$fileserver_url/file/$uploadid/$fileid/$dataname"
    
    return Dict("status" => httpResponse.status, "uploadid" => uploadid, "fileid" => fileid, "url" => url)
end

# Send a simple text message
function send_text_message()
    message_text = "Hello, how are you today?"
    
    env = NATSBridge.smartsend(
        SUBJECT,
        [("message", message_text, "text")],
        nats_url = NATS_URL,
        fileserver_url = FILESERVER_URL,
        fileserverUploadHandler = plik_upload_handler,
        size_threshold = 1_000_000,
        correlation_id = string(uuid4()),
        msg_purpose = "chat",
        sender_name = "user-1"
    )
    
    println("Sent text message with correlation ID: $(env.correlationId)")
end

send_text_message()

Receiver (User 2)

using NATS
using JSON
using UUIDs
using Dates
using PrettyPrinting
using DataFrames
using Arrow
using HTTP
using Base64

# Include the bridge module
include("NATSBridge.jl")
using .NATSBridge

# Configuration
const NATS_URL = "nats://localhost:4222"
const SUBJECT = "/chat/room1"

# Message handler
function message_handler(msg::NATS.Msg)
    payloads = NATSBridge.smartreceive(
        msg,
        max_retries = 5,
        base_delay = 100,
        max_delay = 5000
    )
    
    # Extract the text message
    for (dataname, data, data_type) in payloads
        if data_type == "text"
            println("Received message: $data")
            # Save to file
            write("./received_$dataname.txt", data)
        end
    end
end

# Subscribe to the chat room
NATS.subscribe(SUBJECT) do msg
    message_handler(msg)
end

# Keep the program running
while true
    sleep(1)
end

Step 4: Adding Image Support

Sending an Image

using NATS
using JSON
using UUIDs
using Dates
using PrettyPrinting
using DataFrames
using Arrow
using HTTP
using Base64

include("NATSBridge.jl")
using .NATSBridge

const NATS_URL = "nats://localhost:4222"
const FILESERVER_URL = "http://localhost:8080"
const SUBJECT = "/chat/room1"

function plik_upload_handler(fileserver_url::String, dataname::String, data::Vector{UInt8})::Dict{String, Any}
    url_getUploadID = "$fileserver_url/upload"
    headers = ["Content-Type" => "application/json"]
    body = """{ "OneShot" : true }"""
    httpResponse = HTTP.request("POST", url_getUploadID, headers, body; body_is_form=false)
    responseJson = JSON.parse(String(httpResponse.body))
    uploadid = responseJson["id"]
    uploadtoken = responseJson["uploadToken"]
    
    file_multipart = HTTP.Multipart(dataname, IOBuffer(data), "application/octet-stream")
    url_upload = "$fileserver_url/file/$uploadid"
    headers = ["X-UploadToken" => uploadtoken]
    
    form = HTTP.Form(Dict("file" => file_multipart))
    httpResponse = HTTP.post(url_upload, headers, form)
    responseJson = JSON.parse(String(httpResponse.body))
    
    fileid = responseJson["id"]
    url = "$fileserver_url/file/$uploadid/$fileid/$dataname"
    
    return Dict("status" => httpResponse.status, "uploadid" => uploadid, "fileid" => fileid, "url" => url)
end

function send_image()
    # Read image file
    image_data = read("screenshot.png", Vector{UInt8})
    
    # Send with text message
    env = NATSBridge.smartsend(
        SUBJECT,
        [
            ("text", "Check out this screenshot!", "text"),
            ("screenshot", image_data, "image")
        ],
        nats_url = NATS_URL,
        fileserver_url = FILESERVER_URL,
        fileserverUploadHandler = plik_upload_handler,
        size_threshold = 1_000_000,
        correlation_id = string(uuid4()),
        msg_purpose = "chat",
        sender_name = "user-1"
    )
    
    println("Sent image with correlation ID: $(env.correlationId)")
end

send_image()

Receiving an Image

using NATS
using JSON
using UUIDs
using Dates
using PrettyPrinting
using DataFrames
using Arrow
using HTTP
using Base64

include("NATSBridge.jl")
using .NATSBridge

const NATS_URL = "nats://localhost:4222"
const SUBJECT = "/chat/room1"

function message_handler(msg::NATS.Msg)
    payloads = NATSBridge.smartreceive(
        msg,
        max_retries = 5,
        base_delay = 100,
        max_delay = 5000
    )
    
    for (dataname, data, data_type) in payloads
        if data_type == "text"
            println("Text: $data")
        elseif data_type == "image"
            # Save image to file
            filename = "received_$dataname.bin"
            write(filename, data)
            println("Saved image: $filename")
        end
    end
end

NATS.subscribe(SUBJECT) do msg
    message_handler(msg)
end

Step 5: Handling Large Files with Link Transport

Automatic Transport Selection

using NATS
using JSON
using UUIDs
using Dates
using PrettyPrinting
using DataFrames
using Arrow
using HTTP
using Base64

include("NATSBridge.jl")
using .NATSBridge

const NATS_URL = "nats://localhost:4222"
const FILESERVER_URL = "http://localhost:8080"
const SUBJECT = "/chat/room1"

function plik_upload_handler(fileserver_url::String, dataname::String, data::Vector{UInt8})::Dict{String, Any}
    url_getUploadID = "$fileserver_url/upload"
    headers = ["Content-Type" => "application/json"]
    body = """{ "OneShot" : true }"""
    httpResponse = HTTP.request("POST", url_getUploadID, headers, body; body_is_form=false)
    responseJson = JSON.parse(String(httpResponse.body))
    uploadid = responseJson["id"]
    uploadtoken = responseJson["uploadToken"]
    
    file_multipart = HTTP.Multipart(dataname, IOBuffer(data), "application/octet-stream")
    url_upload = "$fileserver_url/file/$uploadid"
    headers = ["X-UploadToken" => uploadtoken]
    
    form = HTTP.Form(Dict("file" => file_multipart))
    httpResponse = HTTP.post(url_upload, headers, form)
    responseJson = JSON.parse(String(httpResponse.body))
    
    fileid = responseJson["id"]
    url = "$fileserver_url/file/$uploadid/$fileid/$dataname"
    
    return Dict("status" => httpResponse.status, "uploadid" => uploadid, "fileid" => fileid, "url" => url)
end

function send_large_file()
    # Create a large file (> 1MB triggers link transport)
    large_data = rand(10_000_000)  # ~80MB
    
    env = NATSBridge.smartsend(
        SUBJECT,
        [("large_file", large_data, "binary")],
        nats_url = NATS_URL,
        fileserver_url = FILESERVER_URL,
        fileserverUploadHandler = plik_upload_handler,
        size_threshold = 1_000_000,
        correlation_id = string(uuid4()),
        msg_purpose = "chat",
        sender_name = "user-1"
    )
    
    println("Uploaded large file to: $(env.payloads[1].data)")
    println("Correlation ID: $(env.correlationId)")
end

send_large_file()

Step 6: Audio and Video Support

Sending Audio

using NATS
using JSON
using UUIDs
using Dates
using PrettyPrinting
using DataFrames
using Arrow
using HTTP
using Base64

include("NATSBridge.jl")
using .NATSBridge

const NATS_URL = "nats://localhost:4222"
const FILESERVER_URL = "http://localhost:8080"
const SUBJECT = "/chat/room1"

function plik_upload_handler(fileserver_url::String, dataname::String, data::Vector{UInt8})::Dict{String, Any}
    url_getUploadID = "$fileserver_url/upload"
    headers = ["Content-Type" => "application/json"]
    body = """{ "OneShot" : true }"""
    httpResponse = HTTP.request("POST", url_getUploadID, headers, body; body_is_form=false)
    responseJson = JSON.parse(String(httpResponse.body))
    uploadid = responseJson["id"]
    uploadtoken = responseJson["uploadToken"]
    
    file_multipart = HTTP.Multipart(dataname, IOBuffer(data), "application/octet-stream")
    url_upload = "$fileserver_url/file/$uploadid"
    headers = ["X-UploadToken" => uploadtoken]
    
    form = HTTP.Form(Dict("file" => file_multipart))
    httpResponse = HTTP.post(url_upload, headers, form)
    responseJson = JSON.parse(String(httpResponse.body))
    
    fileid = responseJson["id"]
    url = "$fileserver_url/file/$uploadid/$fileid/$dataname"
    
    return Dict("status" => httpResponse.status, "uploadid" => uploadid, "fileid" => fileid, "url" => url)
end

function send_audio()
    # Read audio file (WAV, MP3, etc.)
    audio_data = read("voice_message.mp3", Vector{UInt8})
    
    env = NATSBridge.smartsend(
        SUBJECT,
        [("voice_message", audio_data, "audio")],
        nats_url = NATS_URL,
        fileserver_url = FILESERVER_URL,
        fileserverUploadHandler = plik_upload_handler,
        size_threshold = 1_000_000,
        correlation_id = string(uuid4()),
        msg_purpose = "chat",
        sender_name = "user-1"
    )
    
    println("Sent audio message: $(env.correlationId)")
end

send_audio()

Sending Video

using NATS
using JSON
using UUIDs
using Dates
using PrettyPrinting
using DataFrames
using Arrow
using HTTP
using Base64

include("NATSBridge.jl")
using .NATSBridge

const NATS_URL = "nats://localhost:4222"
const FILESERVER_URL = "http://localhost:8080"
const SUBJECT = "/chat/room1"

function plik_upload_handler(fileserver_url::String, dataname::String, data::Vector{UInt8})::Dict{String, Any}
    url_getUploadID = "$fileserver_url/upload"
    headers = ["Content-Type" => "application/json"]
    body = """{ "OneShot" : true }"""
    httpResponse = HTTP.request("POST", url_getUploadID, headers, body; body_is_form=false)
    responseJson = JSON.parse(String(httpResponse.body))
    uploadid = responseJson["id"]
    uploadtoken = responseJson["uploadToken"]
    
    file_multipart = HTTP.Multipart(dataname, IOBuffer(data), "application/octet-stream")
    url_upload = "$fileserver_url/file/$uploadid"
    headers = ["X-UploadToken" => uploadtoken]
    
    form = HTTP.Form(Dict("file" => file_multipart))
    httpResponse = HTTP.post(url_upload, headers, form)
    responseJson = JSON.parse(String(httpResponse.body))
    
    fileid = responseJson["id"]
    url = "$fileserver_url/file/$uploadid/$fileid/$dataname"
    
    return Dict("status" => httpResponse.status, "uploadid" => uploadid, "fileid" => fileid, "url" => url)
end

function send_video()
    # Read video file (MP4, AVI, etc.)
    video_data = read("video_message.mp4", Vector{UInt8})
    
    env = NATSBridge.smartsend(
        SUBJECT,
        [("video_message", video_data, "video")],
        nats_url = NATS_URL,
        fileserver_url = FILESERVER_URL,
        fileserverUploadHandler = plik_upload_handler,
        size_threshold = 1_000_000,
        correlation_id = string(uuid4()),
        msg_purpose = "chat",
        sender_name = "user-1"
    )
    
    println("Sent video message: $(env.correlationId)")
end

send_video()

Step 7: Table/Data Exchange

Sending Tabular Data

using NATS
using JSON
using UUIDs
using Dates
using PrettyPrinting
using DataFrames
using Arrow
using HTTP
using Base64

include("NATSBridge.jl")
using .NATSBridge

const NATS_URL = "nats://localhost:4222"
const FILESERVER_URL = "http://localhost:8080"
const SUBJECT = "/chat/room1"

function plik_upload_handler(fileserver_url::String, dataname::String, data::Vector{UInt8})::Dict{String, Any}
    url_getUploadID = "$fileserver_url/upload"
    headers = ["Content-Type" => "application/json"]
    body = """{ "OneShot" : true }"""
    httpResponse = HTTP.request("POST", url_getUploadID, headers, body; body_is_form=false)
    responseJson = JSON.parse(String(httpResponse.body))
    uploadid = responseJson["id"]
    uploadtoken = responseJson["uploadToken"]
    
    file_multipart = HTTP.Multipart(dataname, IOBuffer(data), "application/octet-stream")
    url_upload = "$fileserver_url/file/$uploadid"
    headers = ["X-UploadToken" => uploadtoken]
    
    form = HTTP.Form(Dict("file" => file_multipart))
    httpResponse = HTTP.post(url_upload, headers, form)
    responseJson = JSON.parse(String(httpResponse.body))
    
    fileid = responseJson["id"]
    url = "$fileserver_url/file/$uploadid/$fileid/$dataname"
    
    return Dict("status" => httpResponse.status, "uploadid" => uploadid, "fileid" => fileid, "url" => url)
end

function send_table()
    # Create a DataFrame
    df = DataFrame(
        id = 1:5,
        name = ["Alice", "Bob", "Charlie", "Diana", "Eve"],
        score = [95, 88, 92, 98, 85],
        grade = ['A', 'B', 'A', 'B', 'B']
    )
    
    env = NATSBridge.smartsend(
        SUBJECT,
        [("student_scores", df, "table")],
        nats_url = NATS_URL,
        fileserver_url = FILESERVER_URL,
        fileserverUploadHandler = plik_upload_handler,
        size_threshold = 1_000_000,
        correlation_id = string(uuid4()),
        msg_purpose = "chat",
        sender_name = "user-1"
    )
    
    println("Sent table with $(nrow(df)) rows")
end

send_table()

Receiving and Using Tables

using NATS
using JSON
using UUIDs
using Dates
using PrettyPrinting
using DataFrames
using Arrow
using HTTP
using Base64

include("NATSBridge.jl")
using .NATSBridge

const NATS_URL = "nats://localhost:4222"
const SUBJECT = "/chat/room1"

function message_handler(msg::NATS.Msg)
    payloads = NATSBridge.smartreceive(
        msg,
        max_retries = 5,
        base_delay = 100,
        max_delay = 5000
    )
    
    for (dataname, data, data_type) in payloads
        if data_type == "table"
            data = DataFrame(data)
            println("Received table:")
            show(data)
            println("\nAverage score: $(mean(data.score))")
        end
    end
end

NATS.subscribe(SUBJECT) do msg
    message_handler(msg)
end

Step 8: Bidirectional Communication

Request-Response Pattern

using NATS
using JSON
using UUIDs
using Dates
using PrettyPrinting
using DataFrames
using Arrow
using HTTP
using Base64

include("NATSBridge.jl")
using .NATSBridge

const NATS_URL = "nats://localhost:4222"
const SUBJECT = "/api/query"
const REPLY_SUBJECT = "/api/response"

# Request
function send_request()
    query_data = Dict("query" => "SELECT * FROM users")
    
    env = NATSBridge.smartsend(
        SUBJECT,
        [("sql_query", query_data, "dictionary")],
        nats_url = NATS_URL,
        fileserver_url = "http://localhost:8080",
        fileserverUploadHandler = plik_upload_handler,
        size_threshold = 1_000_000,
        correlation_id = string(uuid4()),
        msg_purpose = "request",
        sender_name = "frontend",
        receiver_name = "backend",
        reply_to = REPLY_SUBJECT,
        reply_to_msg_id = string(uuid4())
    )
    
    println("Request sent: $(env.correlationId)")
end

# Response handler
function response_handler(msg::NATS.Msg)
    payloads = NATSBridge.smartreceive(
        msg,
        max_retries = 5,
        base_delay = 100,
        max_delay = 5000
    )
    
    for (dataname, data, data_type) in payloads
        if data_type == "table"
            data = DataFrame(data)
            println("Query results:")
            show(data)
        end
    end
end

NATS.subscribe(REPLY_SUBJECT) do msg
    response_handler(msg)
end

Step 9: Complete Chat Application

Full Chat System

module ChatApp
using NATS
using JSON
using UUIDs
using Dates
using PrettyPrinting
using DataFrames
using Arrow
using HTTP
using Base64

# Include the bridge module
include("../src/NATSBridge.jl")
using .NATSBridge

# Configuration
const NATS_URL = "nats://localhost:4222"
const FILESERVER_URL = "http://localhost:8080"
const SUBJECT = "/chat/room1"

# File upload handler for plik server
function plik_upload_handler(fileserver_url::String, dataname::String, data::Vector{UInt8})::Dict{String, Any}
    url_getUploadID = "$fileserver_url/upload"
    headers = ["Content-Type" => "application/json"]
    body = """{ "OneShot" : true }"""
    httpResponse = HTTP.request("POST", url_getUploadID, headers, body; body_is_form=false)
    responseJson = JSON.parse(String(httpResponse.body))
    uploadid = responseJson["id"]
    uploadtoken = responseJson["uploadToken"]
    
    file_multipart = HTTP.Multipart(dataname, IOBuffer(data), "application/octet-stream")
    url_upload = "$fileserver_url/file/$uploadid"
    headers = ["X-UploadToken" => uploadtoken]
    
    form = HTTP.Form(Dict("file" => file_multipart))
    httpResponse = HTTP.post(url_upload, headers, form)
    responseJson = JSON.parse(String(httpResponse.body))
    
    fileid = responseJson["id"]
    url = "$fileserver_url/file/$uploadid/$fileid/$dataname"
    
    return Dict("status" => httpResponse.status, "uploadid" => uploadid, "fileid" => fileid, "url" => url)
end

function send_chat_message(
    text::String,
    image_path::Union{String, Nothing}=nothing,
    audio_path::Union{String, Nothing}=nothing
)
    # Build payloads list
    payloads = [("message_text", text, "text")]
    
    if image_path !== nothing
        image_data = read(image_path, Vector{UInt8})
        push!(payloads, ("user_image", image_data, "image"))
    end
    
    if audio_path !== nothing
        audio_data = read(audio_path, Vector{UInt8})
        push!(payloads, ("user_audio", audio_data, "audio"))
    end
    
    env = NATSBridge.smartsend(
        SUBJECT,
        payloads,
        nats_url = NATS_URL,
        fileserver_url = FILESERVER_URL,
        fileserverUploadHandler = plik_upload_handler,
        size_threshold = 1_000_000,
        correlation_id = string(uuid4()),
        msg_purpose = "chat",
        sender_name = "user-1"
    )
    
    println("Message sent with correlation ID: $(env.correlationId)")
end

function receive_chat_messages()
    function message_handler(msg::NATS.Msg)
        payloads = NATSBridge.smartreceive(
            msg,
            max_retries = 5,
            base_delay = 100,
            max_delay = 5000
        )
        
        println("\n--- New Message ---")
        for (dataname, data, data_type) in payloads
            if data_type == "text"
                println("Text: $data")
            elseif data_type == "image"
                filename = "received_$dataname.bin"
                write(filename, data)
                println("Image saved: $filename")
            elseif data_type == "audio"
                filename = "received_$dataname.bin"
                write(filename, data)
                println("Audio saved: $filename")
            elseif data_type == "table"
                println("Table received:")
                data = DataFrame(data)
                show(data)
            end
        end
    end
    
    NATS.subscribe(SUBJECT) do msg
        message_handler(msg)
    end
    println("Subscribed to: $SUBJECT")
end

function run_interactive_chat()
    println("\n=== Interactive Chat ===")
    println("1. Send a message")
    println("2. Join a chat room")
    println("3. Exit")
    
    while true
        print("\nSelect option (1-3): ")
        choice = readline()
        
        if choice == "1"
            print("Enter message text: ")
            text = readline()
            send_chat_message(text)
        elseif choice == "2"
            receive_chat_messages()
        elseif choice == "3"
            break
        end
    end
end

end # module

# Run the chat app
using .ChatApp
ChatApp.run_interactive_chat()

Step 10: Testing the Chat System

Test Scenario 1: Text-Only Chat

# Terminal 1: Start the chat receiver
julia test_julia_to_julia_text_receiver.jl

# Terminal 2: Send a message
julia test_julia_to_julia_text_sender.jl

Test Scenario 2: Image Chat

# Terminal 1: Receive messages
julia test_julia_to_julia_mix_payloads_receiver.jl

# Terminal 2: Send image
julia test_julia_to_julia_mix_payload_sender.jl

Test Scenario 3: Large File Transfer

# Terminal 2: Send large file
julia test_julia_to_julia_mix_payload_sender.jl

Conclusion

This walkthrough demonstrated how to build a chat system using NATSBridge.jl with support for:

Text messages
Images (direct transport for small, link transport for large)
Audio files
Video files
Tabular data (DataFrames)
Bidirectional communication
Mixed-content messages

The key takeaways are:

Always wrap payloads in a list - Even for single payloads: [("dataname", data, "type")]
Use appropriate transport - NATSBridge automatically handles size-based routing
Support mixed content - Multiple payloads of different types in one message
Handle errors - Implement proper error handling for network failures
Use correlation IDs - Track messages across distributed systems

For more information, see:

docs/architecture.md - Detailed architecture documentation
docs/implementation.md - Implementation details

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