diff --git a/Manifest.toml b/Manifest.toml
index 15af71d..e55c21a 100644
--- a/Manifest.toml
+++ b/Manifest.toml
@@ -2,7 +2,7 @@
 
 julia_version = "1.11.5"
 manifest_format = "2.0"
-project_hash = "310a130f0609e5376c1f8f5c3b09f0f87b328887"
+project_hash = "a942446c2f26ef72d0c4b0ca522e0adcf709ce4e"
 
 [[deps.AliasTables]]
 deps = ["PtrArrays", "Random"]
@@ -92,11 +92,6 @@ deps = ["Printf"]
 uuid = "ade2ca70-3891-5945-98fb-dc099432e06a"
 version = "1.11.0"
 
-[[deps.Distributed]]
-deps = ["Random", "Serialization", "Sockets"]
-uuid = "8ba89e20-285c-5b6f-9357-94700520ee1b"
-version = "1.11.0"
-
 [[deps.Distributions]]
 deps = ["AliasTables", "FillArrays", "LinearAlgebra", "PDMats", "Printf", "QuadGK", "Random", "SpecialFunctions", "Statistics", "StatsAPI", "StatsBase", "StatsFuns"]
 git-tree-sha1 = "3101c32aab536e7a27b1763c0797dba151b899ad"
@@ -280,16 +275,6 @@ version = "0.3.28"
 uuid = "56ddb016-857b-54e1-b83d-db4d58db5568"
 version = "1.11.0"
 
-[[deps.MQTTClient]]
-deps = ["Distributed", "Random", "Sockets"]
-git-tree-sha1 = "f2597b290d4bf17b577346153cd2ddf9accb5c26"
-uuid = "985f35cc-2c3d-4943-b8c1-f0931d5f0959"
-version = "0.3.1"
-weakdeps = ["PrecompileTools"]
-
-    [deps.MQTTClient.extensions]
-    PrecompileMQTT = "PrecompileTools"
-
 [[deps.Markdown]]
 deps = ["Base64"]
 uuid = "d6f4376e-aef5-505a-96c1-9c027394607a"
diff --git a/Project.toml b/Project.toml
index 1e93b82..5a68284 100644
--- a/Project.toml
+++ b/Project.toml
@@ -10,7 +10,6 @@ DataStructures = "864edb3b-99cc-5e75-8d2d-829cb0a9cfe8"
 Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
 Distributions = "31c24e10-a181-5473-b8eb-7969acd0382f"
 JSON3 = "0f8b85d8-7281-11e9-16c2-39a750bddbf1"
-MQTTClient = "985f35cc-2c3d-4943-b8c1-f0931d5f0959"
 NATS = "55e73f9c-eeeb-467f-b4cc-a633fde63d2a"
 PrettyPrinting = "54e16d92-306c-5ea0-a30b-337be88ac337"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
diff --git a/src/GeneralUtils.jl b/src/GeneralUtils.jl
index 392e4c4..41463b1 100644
--- a/src/GeneralUtils.jl
+++ b/src/GeneralUtils.jl
@@ -2,7 +2,7 @@ module GeneralUtils
     
 
 export  # struct
-        mqttClientInstance,
+        # mqttClientInstance,
         # function
         noNegative!, randomWithProb, randomChoiceWithProb, findIndex, limitvalue 
 
diff --git a/src/communication.jl b/src/communication.jl
index b56609d..f44f77f 100644
--- a/src/communication.jl
+++ b/src/communication.jl
@@ -1,210 +1,211 @@
 module communication
   
-export generate_msgMeta, isMqttConnectionAlive, checkMqttConnection!, 
-        sendMqttMsg, sendReceiveMqttMsg, mqttClientInstance, mqttClientInstance_v2,
-        dataTransferOverMQTT_sender, dataTransferOverMQTT_receiver
+export generate_msgMeta
+        # isMqttConnectionAlive, checkMqttConnection!, 
+        # sendMqttMsg, sendReceiveMqttMsg, mqttClientInstance, mqttClientInstance_v2,
+        # dataTransferOverMQTT_sender, dataTransferOverMQTT_receiver
 
-using JSON3, DataStructures, Distributions, Random, Dates, UUIDs, MQTTClient, DataFrames,
+using JSON3, DataStructures, Distributions, Random, Dates, UUIDs, DataFrames,
       SHA, PrettyPrinting
 using ..util
 
 # ---------------------------------------------- 100 --------------------------------------------- #
 
-abstract type mqttClientInstance end
+# abstract type mqttClientInstance end
 
-mutable struct mqttClientInstance_v1 <: mqttClientInstance
-  mqttBrokerAddress::String
-  mqttBrokerPort::Integer
-  subtopic::Vector{String}
-  receiveDataChannel::Channel
-  onMsgCallback::Function
-  qos::MQTTClient.QOS
-  client::MQTTClient.Client
-  connection::MQTTClient.Connection
-  keepalivetopic::String
-  keepaliveChannel::Channel
-  keepaliveCheckInterval::Integer   # second
-  lastTimeMqttConnCheck::Union{DateTime, Nothing}
-end
+# mutable struct mqttClientInstance_v1 <: mqttClientInstance
+#   mqttBrokerAddress::String
+#   mqttBrokerPort::Integer
+#   subtopic::Vector{String}
+#   receiveDataChannel::Channel
+#   onMsgCallback::Function
+#   qos::MQTTClient.QOS
+#   client::MQTTClient.Client
+#   connection::MQTTClient.Connection
+#   keepalivetopic::String
+#   keepaliveChannel::Channel
+#   keepaliveCheckInterval::Integer   # second
+#   lastTimeMqttConnCheck::Union{DateTime, Nothing}
+# end
 
-function mqttClientInstance_v1(
-    mqttBrokerAddress::String,
-    mqttBrokerPort::Integer,
-    subtopic::Vector{String},
-    receiveDataChannel::Channel,
-    keepaliveChannel::Channel,  # user needs to specify because it has to be accessible by user-defined onMsgCallback()
-    onMsgCallback::Function
-    ;
-    keepalivetopic::String= "/keepalive/$(uuid4snakecase())",
-    keepaliveCheckInterval::Integer=30,
-    qos::MQTTClient.QOS=QOS_1,
-  )
+# function mqttClientInstance_v1(
+#     mqttBrokerAddress::String,
+#     mqttBrokerPort::Integer,
+#     subtopic::Vector{String},
+#     receiveDataChannel::Channel,
+#     keepaliveChannel::Channel,  # user needs to specify because it has to be accessible by user-defined onMsgCallback()
+#     onMsgCallback::Function
+#     ;
+#     keepalivetopic::String= "/keepalive/$(uuid4snakecase())",
+#     keepaliveCheckInterval::Integer=30,
+#     qos::MQTTClient.QOS=QOS_1,
+#   )
   
-  client, connection = MQTTClient.MakeConnection(mqttBrokerAddress, mqttBrokerPort)
-  MQTTClient.connect(client, connection)
-  for i in subtopic
-    MQTTClient.subscribe(client, i, onMsgCallback, qos=qos)
-  end
-  MQTTClient.subscribe(client, keepalivetopic, onMsgCallback, qos=qos)
+#   client, connection = MQTTClient.MakeConnection(mqttBrokerAddress, mqttBrokerPort)
+#   MQTTClient.connect(client, connection)
+#   for i in subtopic
+#     MQTTClient.subscribe(client, i, onMsgCallback, qos=qos)
+#   end
+#   MQTTClient.subscribe(client, keepalivetopic, onMsgCallback, qos=qos)
 
-  instance = mqttClientInstance(
-    mqttBrokerAddress,
-    mqttBrokerPort,
-    subtopic,
-    receiveDataChannel,
-    onMsgCallback,
-    qos,
-    client,
-    connection,
-    keepalivetopic,
-    keepaliveChannel,
-    keepaliveCheckInterval,
-    Dates.now(),
-  )
+#   instance = mqttClientInstance(
+#     mqttBrokerAddress,
+#     mqttBrokerPort,
+#     subtopic,
+#     receiveDataChannel,
+#     onMsgCallback,
+#     qos,
+#     client,
+#     connection,
+#     keepalivetopic,
+#     keepaliveChannel,
+#     keepaliveCheckInterval,
+#     Dates.now(),
+#   )
 
-  return instance
-end
+#   return instance
+# end
 
 
-mutable struct mqttClientInstance_v2 <: mqttClientInstance
-  mqttBrokerAddress::String
-  mqttBrokerPort::Integer
-  subtopic::Vector{String}
-  msgReceiveChannel
-  onMsgCallback::Function
-  qos::MQTTClient.QOS
-  client::MQTTClient.Client
-  clientId::String
-  connection::MQTTClient.Connection
-  keepalivetopic::String
-  keepaliveChannel::Channel
-  keepaliveCheckInterval::Integer   # second
-  lastTimeMqttConnCheck::Union{DateTime, Nothing}
-  multiMsg::String  # "single", "metadata", "datapart"
-  latestMsg
-end
-""" MQTT client v2. The difference between client v1 and v2 is v2 allows multiple 
-  msgReceiveChannel without having to redefine mqttClientInstance again like in v1.
-  This is achieved by using msgReceiveChannel::NamedTuple to store multiple channel.
-# Arguments
-  - `mqttBrokerAddress`
-      MQTT broker address. Can be URL or IP address 
-  - `subtopic`
-    A list of topic to be subscribed Ex. ["/testopic_1", "/testopic_2"]
-  - `msgReceiveChannel`
-    A storage the mqtt client used to store incoming message. 
-    Ex. msgReceiveChannel = (ch1=Channel(8), ch2=Channel(32))
-  - `keepaliveChannel`
-    A channel to store keepalive message
-  - `onMsgCallback`
-    A user-defined function to handle incoming message
+# mutable struct mqttClientInstance_v2 <: mqttClientInstance
+#   mqttBrokerAddress::String
+#   mqttBrokerPort::Integer
+#   subtopic::Vector{String}
+#   msgReceiveChannel
+#   onMsgCallback::Function
+#   qos::MQTTClient.QOS
+#   client::MQTTClient.Client
+#   clientId::String
+#   connection::MQTTClient.Connection
+#   keepalivetopic::String
+#   keepaliveChannel::Channel
+#   keepaliveCheckInterval::Integer   # second
+#   lastTimeMqttConnCheck::Union{DateTime, Nothing}
+#   multiMsg::String  # "single", "metadata", "datapart"
+#   latestMsg
+# end
+# """ MQTT client v2. The difference between client v1 and v2 is v2 allows multiple 
+#   msgReceiveChannel without having to redefine mqttClientInstance again like in v1.
+#   This is achieved by using msgReceiveChannel::NamedTuple to store multiple channel.
+# # Arguments
+#   - `mqttBrokerAddress`
+#       MQTT broker address. Can be URL or IP address 
+#   - `subtopic`
+#     A list of topic to be subscribed Ex. ["/testopic_1", "/testopic_2"]
+#   - `msgReceiveChannel`
+#     A storage the mqtt client used to store incoming message. 
+#     Ex. msgReceiveChannel = (ch1=Channel(8), ch2=Channel(32))
+#   - `keepaliveChannel`
+#     A channel to store keepalive message
+#   - `onMsgCallback`
+#     A user-defined function to handle incoming message
 
-# Keyword Arguments
-  - `mqttBrokerPort`
-      mqtt broker port
-  - `keepalivetopic`
-    A topic where keepalive message going
-  - `keepaliveCheckInterval`
-    A time interval to check whether the mqtt client still connect to mqtt broker 
-  - `qos`
-    Quality of Service. Can be QOS_0, QOS_1, QOS_2
-  - `clearOldMsg`
-    Boolean to determine if old messages should be cleared from channels
+# # Keyword Arguments
+#   - `mqttBrokerPort`
+#       mqtt broker port
+#   - `keepalivetopic`
+#     A topic where keepalive message going
+#   - `keepaliveCheckInterval`
+#     A time interval to check whether the mqtt client still connect to mqtt broker 
+#   - `qos`
+#     Quality of Service. Can be QOS_0, QOS_1, QOS_2
+#   - `clearOldMsg`
+#     Boolean to determine if old messages should be cleared from channels
 
-# Return
-  - `mqttInstance`
-    A new mqtt client
+# # Return
+#   - `mqttInstance`
+#     A new mqtt client
 
-# Example
-  ```jldoctest
-  julia> using Revise
-  julia> using GeneralUtils, Dates, JSON3, UUIDs
-  julia> mqttMsgReceiveTopic = ["/receivetopic_1", "/receivetopic_2"]
-  julia> mqttMsgReceiveChannel = (ch1=Channel(8), ch2=Channel(32))  # single channel Ex. (ch1=Channel(8),)
-  julia> keepaliveChannel = Channel(8)
-  julia> function onMsgCallback(topic, payload)
-            jobj = JSON3.read(String(payload))
-            incomingMqttMsg = copy(jobj)  # convert json object into julia dictionary recursively
+# # Example
+#   ```jldoctest
+#   julia> using Revise
+#   julia> using GeneralUtils, Dates, JSON3, UUIDs
+#   julia> mqttMsgReceiveTopic = ["/receivetopic_1", "/receivetopic_2"]
+#   julia> mqttMsgReceiveChannel = (ch1=Channel(8), ch2=Channel(32))  # single channel Ex. (ch1=Channel(8),)
+#   julia> keepaliveChannel = Channel(8)
+#   julia> function onMsgCallback(topic, payload)
+#             jobj = JSON3.read(String(payload))
+#             incomingMqttMsg = copy(jobj)  # convert json object into julia dictionary recursively
             
-            if occursin("topic_1", topic)
-              put!(mqttMsgReceiveChannel[:ch1], incomingMqttMsg)
-            elseif occursin("topic_2", topic)
-              put!(mqttMsgReceiveChannel[:ch2], incomingMqttMsg)
-            elseif occursin("keepalive", topic)
-              put!(keepaliveChannel, incomingMqttMsg)
-            else
-              println("undefined condition ", @__FILE__, " ", @__LINE__)
-            end
-          end
-  julia> mqttInstance = GeneralUtils.mqttClientInstance_v2(
-                          "mqtt.yiem.cc",
-                          mqttMsgReceiveTopic,
-                          mqttMsgReceiveChannel,
-                          keepaliveChannel,
-                          onMsgCallback
-                        )
-  ```
+#             if occursin("topic_1", topic)
+#               put!(mqttMsgReceiveChannel[:ch1], incomingMqttMsg)
+#             elseif occursin("topic_2", topic)
+#               put!(mqttMsgReceiveChannel[:ch2], incomingMqttMsg)
+#             elseif occursin("keepalive", topic)
+#               put!(keepaliveChannel, incomingMqttMsg)
+#             else
+#               println("undefined condition ", @__FILE__, " ", @__LINE__)
+#             end
+#           end
+#   julia> mqttInstance = GeneralUtils.mqttClientInstance_v2(
+#                           "mqtt.yiem.cc",
+#                           mqttMsgReceiveTopic,
+#                           mqttMsgReceiveChannel,
+#                           keepaliveChannel,
+#                           onMsgCallback
+#                         )
+#   ```
 
-# Signature
-"""
-function mqttClientInstance_v2(
-    mqttBrokerAddress::String,
-    subtopic::Vector{String},
-    msgReceiveChannel, # NamedTuple of channels i.e. msgReceiveChannel = (ch1=Channel(8), ch2=Channel(8))
-    keepaliveChannel::Channel,  # used for checkMqttConnection(). user needs to specify because it has to be accessible by user-defined onMsgCallback()
-    onMsgCallback::Function
-    ;
-    clientId::String="NA",
-    mqttBrokerPort::Integer=1883,
-    keepaliveTopic::String= "/keepalive/$(uuid4snakecase())",
-    keepaliveCheckInterval::Integer=30,
-    qos::MQTTClient.QOS=QOS_1,
-    multiMsg::String="single",  #[PENDING] bad design. this info should be stored in each msgMeta
-    clearOldMsg::Bool=true,
-  )
+# # Signature
+# """
+# function mqttClientInstance_v2(
+#     mqttBrokerAddress::String,
+#     subtopic::Vector{String},
+#     msgReceiveChannel, # NamedTuple of channels i.e. msgReceiveChannel = (ch1=Channel(8), ch2=Channel(8))
+#     keepaliveChannel::Channel,  # used for checkMqttConnection(). user needs to specify because it has to be accessible by user-defined onMsgCallback()
+#     onMsgCallback::Function
+#     ;
+#     clientId::String="NA",
+#     mqttBrokerPort::Integer=1883,
+#     keepaliveTopic::String= "/keepalive/$(uuid4snakecase())",
+#     keepaliveCheckInterval::Integer=30,
+#     qos::MQTTClient.QOS=QOS_1,
+#     multiMsg::String="single",  #[PENDING] bad design. this info should be stored in each msgMeta
+#     clearOldMsg::Bool=true,
+#   )
   
-  client, connection = MQTTClient.MakeConnection(mqttBrokerAddress, mqttBrokerPort)
-  MQTTClient.connect(client, connection)
-  for i in subtopic
-    MQTTClient.subscribe(client, i, onMsgCallback, qos=qos)
-  end
-  MQTTClient.subscribe(client, keepaliveTopic, onMsgCallback, qos=qos)
+#   client, connection = MQTTClient.MakeConnection(mqttBrokerAddress, mqttBrokerPort)
+#   MQTTClient.connect(client, connection)
+#   for i in subtopic
+#     MQTTClient.subscribe(client, i, onMsgCallback, qos=qos)
+#   end
+#   MQTTClient.subscribe(client, keepaliveTopic, onMsgCallback, qos=qos)
 
-  keepaliveTopic = clientId == "NA" ? keepaliveTopic : "/keepalive/$clientId"
+#   keepaliveTopic = clientId == "NA" ? keepaliveTopic : "/keepalive/$clientId"
 
-  instance = mqttClientInstance_v2(
-    mqttBrokerAddress,
-    mqttBrokerPort,
-    subtopic,
-    msgReceiveChannel,
-    onMsgCallback,
-    qos,
-    client,
-    clientId,
-    connection,
-    keepaliveTopic,
-    keepaliveChannel,
-    keepaliveCheckInterval,
-    nothing,
-    multiMsg,
-    nothing,  # store latest message to prevent doing the same massage twice
-  )
+#   instance = mqttClientInstance_v2(
+#     mqttBrokerAddress,
+#     mqttBrokerPort,
+#     subtopic,
+#     msgReceiveChannel,
+#     onMsgCallback,
+#     qos,
+#     client,
+#     clientId,
+#     connection,
+#     keepaliveTopic,
+#     keepaliveChannel,
+#     keepaliveCheckInterval,
+#     nothing,
+#     multiMsg,
+#     nothing,  # store latest message to prevent doing the same massage twice
+#   )
 
-  if clearOldMsg
-    chnames = keys(msgReceiveChannel)
-    for i in chnames
-      totalmsg = msgReceiveChannel[i].n_avail_items #[TESTING]
-      if totalmsg > 0
-        while isready(msgReceiveChannel[i])
-          _ = take!(msgReceiveChannel[i])
-        end
-        println("Total $totalmsg old MQTT messages cleared ", @__FILE__, ":", @__LINE__, " $(Dates.now())")
-      end
-    end
-  end
+#   if clearOldMsg
+#     chnames = keys(msgReceiveChannel)
+#     for i in chnames
+#       totalmsg = msgReceiveChannel[i].n_avail_items #[TESTING]
+#       if totalmsg > 0
+#         while isready(msgReceiveChannel[i])
+#           _ = take!(msgReceiveChannel[i])
+#         end
+#         println("Total $totalmsg old MQTT messages cleared ", @__FILE__, ":", @__LINE__, " $(Dates.now())")
+#       end
+#     end
+#   end
 
-  return instance
-end
+#   return instance
+# end
 
 
 """ Generate msgMeta to be including in a message. So the message receiver know 
@@ -324,551 +325,551 @@ end
 
 
 
-""" Check mqtt server connection.
+# """ Check mqtt server connection.
 
-  Arguments\n
-  -----
-    mqttInstanceDict::Dict{Symbol, Any}
-      a dictionary contain mqtt instance. 1 per mqtt client.
-    interval::Integer
-      time interval to check mqtt server in seconds
+#   Arguments\n
+#   -----
+#     mqttInstanceDict::Dict{Symbol, Any}
+#       a dictionary contain mqtt instance. 1 per mqtt client.
+#     interval::Integer
+#       time interval to check mqtt server in seconds
 
-  Return\n
-  -----
-    isconnectionalive::Bool
-      true if mqtt connection is alive
+#   Return\n
+#   -----
+#     isconnectionalive::Bool
+#       true if mqtt connection is alive
 
-  Example\n
-  -----
-  ```jldoctest
-  julia> using Revise
-  julia> using GeneralUtils, Dates, JSON3, MQTTClient
-  julia> GeneralUtils.isMqttConnectionAlive(mqttInstance)
-  true
-  ```
+#   Example\n
+#   -----
+#   ```jldoctest
+#   julia> using Revise
+#   julia> using GeneralUtils, Dates, JSON3, MQTTClient
+#   julia> GeneralUtils.isMqttConnectionAlive(mqttInstance)
+#   true
+#   ```
 
-  Signature\n
-  -----
-"""
-function isMqttConnectionAlive(mqttInstance::T)::Bool where {T<:mqttClientInstance}
-  isconnectionalive = false
+#   Signature\n
+#   -----
+# """
+# function isMqttConnectionAlive(mqttInstance::T)::Bool where {T<:mqttClientInstance}
+#   isconnectionalive = false
 
-  # ditch old keepalive msg is any
-  while isready(mqttInstance.keepaliveChannel)
-    _ = take!(mqttInstance.keepaliveChannel)
-  end
+#   # ditch old keepalive msg is any
+#   while isready(mqttInstance.keepaliveChannel)
+#     _ = take!(mqttInstance.keepaliveChannel)
+#   end
 
-  msgMeta = generate_msgMeta(
-    mqttInstance.keepalivetopic,
-    msgPurpose= "keepalive",
-  )
+#   msgMeta = generate_msgMeta(
+#     mqttInstance.keepalivetopic,
+#     msgPurpose= "keepalive",
+#   )
 
-  keepaliveMsg = Dict(
-    :msgMeta=> msgMeta,
-    :payload=> Dict(
-      :text=>"keepalive",
-    )
-  )
+#   keepaliveMsg = Dict(
+#     :msgMeta=> msgMeta,
+#     :payload=> Dict(
+#       :text=>"keepalive",
+#     )
+#   )
   
-  publish(mqttInstance.client, keepaliveMsg[:msgMeta][:sendTo], 
-          JSON3.write(keepaliveMsg))
-  timediff = 0
-  starttime = Dates.now()
-  while timediff <= 5
-    timediff = timedifference(starttime, Dates.now(), "seconds")
-    if isready(mqttInstance.keepaliveChannel)
-      incomingMsg = take!(mqttInstance.keepaliveChannel)
-      if incomingMsg[:msgMeta][:msgId] == keepaliveMsg[:msgMeta][:msgId]
-        # connection is alive
-        isconnectionalive = true
-        break
-      end
-    end
-    sleep(1)
-  end
-  return isconnectionalive
-end
+#   publish(mqttInstance.client, keepaliveMsg[:msgMeta][:sendTo], 
+#           JSON3.write(keepaliveMsg))
+#   timediff = 0
+#   starttime = Dates.now()
+#   while timediff <= 5
+#     timediff = timedifference(starttime, Dates.now(), "seconds")
+#     if isready(mqttInstance.keepaliveChannel)
+#       incomingMsg = take!(mqttInstance.keepaliveChannel)
+#       if incomingMsg[:msgMeta][:msgId] == keepaliveMsg[:msgMeta][:msgId]
+#         # connection is alive
+#         isconnectionalive = true
+#         break
+#       end
+#     end
+#     sleep(1)
+#   end
+#   return isconnectionalive
+# end
 
 
-""" Check mqtt server connection, reconnect if disconnected.
+# """ Check mqtt server connection, reconnect if disconnected.
 
-  Arguments\n
-  -----
-    mqttInstanceDict::Dict{Symbol, Any}
-      a dictionary contain mqtt instance. 1 per mqtt client.
-    keepaliveCheckInterval::Integer
-      time interval to check mqtt server in seconds
+#   Arguments\n
+#   -----
+#     mqttInstanceDict::Dict{Symbol, Any}
+#       a dictionary contain mqtt instance. 1 per mqtt client.
+#     keepaliveCheckInterval::Integer
+#       time interval to check mqtt server in seconds
 
-  Return\n
-  -----
-    isreconnect::Bool
-      true if mqtt connection is reconnected
+#   Return\n
+#   -----
+#     isreconnect::Bool
+#       true if mqtt connection is reconnected
 
-  Example\n
-  -----
-  ```jldoctest
-  julia> using Revise
-  julia> using GeneralUtils, Dates, JSON3
-  julia> GeneralUtils.checkMqttConnection!(mqttInstance, 5)
-  ```
+#   Example\n
+#   -----
+#   ```jldoctest
+#   julia> using Revise
+#   julia> using GeneralUtils, Dates, JSON3
+#   julia> GeneralUtils.checkMqttConnection!(mqttInstance, 5)
+#   ```
 
-  Signature\n
-  -----
-"""
-function checkMqttConnection!(mqttInstance::T; 
-  keepaliveCheckInterval::Union{Integer, Nothing}=nothing)::Union{Bool, Nothing} where {T<:mqttClientInstance}
+#   Signature\n
+#   -----
+# """
+# function checkMqttConnection!(mqttInstance::T; 
+#   keepaliveCheckInterval::Union{Integer, Nothing}=nothing)::Union{Bool, Nothing} where {T<:mqttClientInstance}
 
-  interval = keepaliveCheckInterval !== nothing ? keepaliveCheckInterval : mqttInstance.keepaliveCheckInterval
+#   interval = keepaliveCheckInterval !== nothing ? keepaliveCheckInterval : mqttInstance.keepaliveCheckInterval
 
-  # check if mqtt connection is still up
-  intervaldiff = 
-  if mqttInstance.lastTimeMqttConnCheck !== nothing
-    timedifference(mqttInstance.lastTimeMqttConnCheck, Dates.now(), "seconds")
-  else 
-    Inf
-  end
+#   # check if mqtt connection is still up
+#   intervaldiff = 
+#   if mqttInstance.lastTimeMqttConnCheck !== nothing
+#     timedifference(mqttInstance.lastTimeMqttConnCheck, Dates.now(), "seconds")
+#   else 
+#     Inf
+#   end
 
-  if intervaldiff > interval
-    connectionStatusStart = isMqttConnectionAlive(mqttInstance) # a flag to note whether the connection status has changed from false to true 
-    while true
-      mqttConnStatus = isMqttConnectionAlive(mqttInstance) 
-      if mqttConnStatus == false
-        sleep(5) # wait
-        println("MQTT connection disconnected, attemping to reconnect $(Dates.now()) at $(mqttInstance.mqttBrokerAddress):$(mqttInstance.mqttBrokerPort)")
-        # use new client to reconnect instead of the previous one because I don't want to modify MQTTClient.jl yet
-        mqttInstance.client, mqttInstance.connection = 
-                        MakeConnection(mqttInstance.mqttBrokerAddress,
-                                      mqttInstance.mqttBrokerPort)
-        try
-          connect(mqttInstance.client, mqttInstance.connection)
-          for topic in mqttInstance.subtopic
-            subscribe(mqttInstance.client, topic, mqttInstance.onMsgCallback, qos=mqttInstance.qos)
-          end
-          MQTTClient.subscribe(mqttInstance.client, mqttInstance.keepalivetopic, mqttInstance.onMsgCallback, qos=mqttInstance.qos)
-        catch
-          println("Failed to reconnect MQTT broker at $(mqttInstance.mqttBrokerAddress):$(mqttInstance.mqttBrokerPort) $(Dates.now())")
-        end
-      else 
-        mqttInstance.lastTimeMqttConnCheck = Dates.now()
-        if connectionStatusStart != mqttConnStatus
-          println("Reconnected to MQTT broker at $(mqttInstance.mqttBrokerAddress):$(mqttInstance.mqttBrokerPort) $(Dates.now())")
-        end
-        return mqttConnStatus
-      end
-    end
-  else
-    return nothing  # still within check interval, no update on connection status yet
-  end
-end
+#   if intervaldiff > interval
+#     connectionStatusStart = isMqttConnectionAlive(mqttInstance) # a flag to note whether the connection status has changed from false to true 
+#     while true
+#       mqttConnStatus = isMqttConnectionAlive(mqttInstance) 
+#       if mqttConnStatus == false
+#         sleep(5) # wait
+#         println("MQTT connection disconnected, attemping to reconnect $(Dates.now()) at $(mqttInstance.mqttBrokerAddress):$(mqttInstance.mqttBrokerPort)")
+#         # use new client to reconnect instead of the previous one because I don't want to modify MQTTClient.jl yet
+#         mqttInstance.client, mqttInstance.connection = 
+#                         MakeConnection(mqttInstance.mqttBrokerAddress,
+#                                       mqttInstance.mqttBrokerPort)
+#         try
+#           connect(mqttInstance.client, mqttInstance.connection)
+#           for topic in mqttInstance.subtopic
+#             subscribe(mqttInstance.client, topic, mqttInstance.onMsgCallback, qos=mqttInstance.qos)
+#           end
+#           MQTTClient.subscribe(mqttInstance.client, mqttInstance.keepalivetopic, mqttInstance.onMsgCallback, qos=mqttInstance.qos)
+#         catch
+#           println("Failed to reconnect MQTT broker at $(mqttInstance.mqttBrokerAddress):$(mqttInstance.mqttBrokerPort) $(Dates.now())")
+#         end
+#       else 
+#         mqttInstance.lastTimeMqttConnCheck = Dates.now()
+#         if connectionStatusStart != mqttConnStatus
+#           println("Reconnected to MQTT broker at $(mqttInstance.mqttBrokerAddress):$(mqttInstance.mqttBrokerPort) $(Dates.now())")
+#         end
+#         return mqttConnStatus
+#       end
+#     end
+#   else
+#     return nothing  # still within check interval, no update on connection status yet
+#   end
+# end
 
 
-""" Send a message to specified MQTT topic then wait for reply.
+# """ Send a message to specified MQTT topic then wait for reply.
 
-#  Arguments
-  - `outgoingMsg::Dict`
-      an outgoing message
+# #  Arguments
+#   - `outgoingMsg::Dict`
+#       an outgoing message
 
-#  Return
-  - `result::NamedTuple`
-    ( success= true, error= nothing )
+# #  Return
+#   - `result::NamedTuple`
+#     ( success= true, error= nothing )
 
-#  Example
-  ```jldoctest
-  julia> using Revise
-  julia> using GeneralUtils, Dates, JSON3, UUIDs
-  julia> msgMeta = GeneralUtils.generate_msgMeta(
-            "/testtopic",
-            senderName= "somename",
-            senderId= uuid4snakecase(),
-            mqttBrokerAddress= "test.mosquitto.org",
-            mqttBrokerPort= 1883,
-          )
-  julia> outgoingMsg = Dict(
-            :msgMeta=> msgMeta,
-            :payload=> Dict("hello"=> "World"),
-          )
-  julia> success, error = GeneralUtils.sendMqttMsg(outgoingMsg)
-  ```
+# #  Example
+#   ```jldoctest
+#   julia> using Revise
+#   julia> using GeneralUtils, Dates, JSON3, UUIDs
+#   julia> msgMeta = GeneralUtils.generate_msgMeta(
+#             "/testtopic",
+#             senderName= "somename",
+#             senderId= uuid4snakecase(),
+#             mqttBrokerAddress= "test.mosquitto.org",
+#             mqttBrokerPort= 1883,
+#           )
+#   julia> outgoingMsg = Dict(
+#             :msgMeta=> msgMeta,
+#             :payload=> Dict("hello"=> "World"),
+#           )
+#   julia> success, error = GeneralUtils.sendMqttMsg(outgoingMsg)
+#   ```
 
-#  Signature
-"""
-function sendMqttMsg(outgoingMsg::Dict{Symbol, T})::NamedTuple where {T<:Any}
+# #  Signature
+# """
+# function sendMqttMsg(outgoingMsg::Dict{Symbol, T})::NamedTuple where {T<:Any}
 
-  # sendMqttMsg() doesn't need to receive msg but mqttClientInstance_v2 requires to have receive topic
-  mqttMsgReceiveTopic = "/GeneralUtils_sendMqttMsg/$(outgoingMsg[:msgMeta][:senderId])"
+#   # sendMqttMsg() doesn't need to receive msg but mqttClientInstance_v2 requires to have receive topic
+#   mqttMsgReceiveTopic = "/GeneralUtils_sendMqttMsg/$(outgoingMsg[:msgMeta][:senderId])"
 
-  mqttMsgReceiveChannel = (ch1=Channel(8),)
-  keepaliveChannel = Channel(8)
+#   mqttMsgReceiveChannel = (ch1=Channel(8),)
+#   keepaliveChannel = Channel(8)
 
-  # Define the callback for receiving messages.
-  function onMsgCallback(topic, payload)
-    jobj = JSON3.read(String(payload))
-    onMsg = copy(jobj)
-    put!(mqttMsgReceiveChannel[:ch1], onMsg)
-  end
+#   # Define the callback for receiving messages.
+#   function onMsgCallback(topic, payload)
+#     jobj = JSON3.read(String(payload))
+#     onMsg = copy(jobj)
+#     put!(mqttMsgReceiveChannel[:ch1], onMsg)
+#   end
 
-  mqttInstance = mqttClientInstance_v2(
-    outgoingMsg[:msgMeta][:mqttBrokerAddress],
-    [mqttMsgReceiveTopic],
-    mqttMsgReceiveChannel,
-    keepaliveChannel,
-    onMsgCallback;
-    mqttBrokerPort=outgoingMsg[:msgMeta][:mqttBrokerPort]
-  )
+#   mqttInstance = mqttClientInstance_v2(
+#     outgoingMsg[:msgMeta][:mqttBrokerAddress],
+#     [mqttMsgReceiveTopic],
+#     mqttMsgReceiveChannel,
+#     keepaliveChannel,
+#     onMsgCallback;
+#     mqttBrokerPort=outgoingMsg[:msgMeta][:mqttBrokerPort]
+#   )
 
-  response = sendMqttMsg(mqttInstance, outgoingMsg)
-  try disconnect(mqttInstance.client) catch end
+#   response = sendMqttMsg(mqttInstance, outgoingMsg)
+#   try disconnect(mqttInstance.client) catch end
 
-  return response
-end
-function sendMqttMsg(mqttInstance::mqttClientInstance, outgoingMsg::Dict{Symbol, T}
-  )::NamedTuple where {T<:Any}
-  try
-    publish(mqttInstance.client, outgoingMsg[:msgMeta][:sendTo], JSON3.write(outgoingMsg)) 
-    return (success=true, error=nothing)
-  catch e
-    return (success=false, error=e)
-  end
-end
+#   return response
+# end
+# function sendMqttMsg(mqttInstance::mqttClientInstance, outgoingMsg::Dict{Symbol, T}
+#   )::NamedTuple where {T<:Any}
+#   try
+#     publish(mqttInstance.client, outgoingMsg[:msgMeta][:sendTo], JSON3.write(outgoingMsg)) 
+#     return (success=true, error=nothing)
+#   catch e
+#     return (success=false, error=e)
+#   end
+# end
 
 
-""" Send a message to specified MQTT topic then wait for reply.
+# """ Send a message to specified MQTT topic then wait for reply.
 
-# Arguments
-  - `outgoingMsg::Dict{Symbol, T}`
-    an outgoing message
+# # Arguments
+#   - `outgoingMsg::Dict{Symbol, T}`
+#     an outgoing message
 
-# Keyword Arguments
-  - `timeout::Integer=60`
-    time in seconds to wait for a response before error
-  - `maxattempt::Integer=1`
-    maximum number of attempts to send and receive message
+# # Keyword Arguments
+#   - `timeout::Integer=60`
+#     time in seconds to wait for a response before error
+#   - `maxattempt::Integer=1`
+#     maximum number of attempts to send and receive message
 
-# Return
-  - `result::NamedTuple`
-  ( 
-    success= true,    # idicates whether sending MQTT message successful
-    error= nothing   # error message
-    response= somemessage  # response message
-  )
+# # Return
+#   - `result::NamedTuple`
+#   ( 
+#     success= true,    # idicates whether sending MQTT message successful
+#     error= nothing   # error message
+#     response= somemessage  # response message
+#   )
 
-# Example
-```jldoctest
-julia> using Revise
-julia> using GeneralUtils, Dates, UUIDs, JSON3
-julia> msgMeta = GeneralUtils.generate_msgMeta(
-          "/testtopic",
-          senderName= "somename",
-          senderId= uuid4snakecase(),
-          mqttBrokerAddress= "mqtt.yiem.cc",
-          mqttBrokerPort= 1883,
-        )
-julia> outgoingMsg = Dict(
-          :msgMeta=> msgMeta,
-          :payload=> Dict(:hello=> "World"),
-        )
-julia> success, error, response = GeneralUtils.sendReceiveMqttMsg(outgoingMsg)
-```
+# # Example
+# ```jldoctest
+# julia> using Revise
+# julia> using GeneralUtils, Dates, UUIDs, JSON3
+# julia> msgMeta = GeneralUtils.generate_msgMeta(
+#           "/testtopic",
+#           senderName= "somename",
+#           senderId= uuid4snakecase(),
+#           mqttBrokerAddress= "mqtt.yiem.cc",
+#           mqttBrokerPort= 1883,
+#         )
+# julia> outgoingMsg = Dict(
+#           :msgMeta=> msgMeta,
+#           :payload=> Dict(:hello=> "World"),
+#         )
+# julia> success, error, response = GeneralUtils.sendReceiveMqttMsg(outgoingMsg)
+# ```
 
-# Signature
-"""
-function sendReceiveMqttMsg(outgoingMsg::Dict{Symbol, T};
-  connectiontimeout::Integer=600, responsetimeout::Integer=60, responsemaxattempt::Integer=1)::NamedTuple where {T<:Any}
-  senderId = outgoingMsg[:msgMeta][:senderId]
-  mqttMsgReceiveTopic = "/GeneralUtils_sendReceiveMqttMsg/$senderId"
-  mqttMsgReceiveChannel = (ch1=Channel(8),)
-  keepaliveChannel = Channel(8)
-  outgoingMsg[:msgMeta][:replyTopic] = mqttMsgReceiveTopic
+# # Signature
+# """
+# function sendReceiveMqttMsg(outgoingMsg::Dict{Symbol, T};
+#   connectiontimeout::Integer=600, responsetimeout::Integer=60, responsemaxattempt::Integer=1)::NamedTuple where {T<:Any}
+#   senderId = outgoingMsg[:msgMeta][:senderId]
+#   mqttMsgReceiveTopic = "/GeneralUtils_sendReceiveMqttMsg/$senderId"
+#   mqttMsgReceiveChannel = (ch1=Channel(8),)
+#   keepaliveChannel = Channel(8)
+#   outgoingMsg[:msgMeta][:replyTopic] = mqttMsgReceiveTopic
 
-  # Define the callback for receiving messages.
-  function onMsgCallback(topic, payload)
-    jobj = JSON3.read(String(payload))
-    incomingMqttMsg = copy(jobj)
+#   # Define the callback for receiving messages.
+#   function onMsgCallback(topic, payload)
+#     jobj = JSON3.read(String(payload))
+#     incomingMqttMsg = copy(jobj)
 
-    if occursin("GeneralUtils_sendReceiveMqttMsg", topic)
-      put!(mqttMsgReceiveChannel[:ch1], incomingMqttMsg)
-    elseif occursin("keepalive", topic)
-      put!(keepaliveChannel, incomingMqttMsg)
-    else
-      println("undefined condition ", @__FILE__, " ", @__LINE__)
-    end
-  end
+#     if occursin("GeneralUtils_sendReceiveMqttMsg", topic)
+#       put!(mqttMsgReceiveChannel[:ch1], incomingMqttMsg)
+#     elseif occursin("keepalive", topic)
+#       put!(keepaliveChannel, incomingMqttMsg)
+#     else
+#       println("undefined condition ", @__FILE__, " ", @__LINE__)
+#     end
+#   end
   
-  mqttInstance = nothing
-  attempt = 0
-  starttime = Dates.now()
-  endtime = starttime + Second(connectiontimeout)
-  errormsg = nothing
-  while true
-    timenow = Dates.now()
-    timepass = timedifference(starttime, timenow, "seconds")
-    timeleft = timedifference(timenow, endtime, "seconds")
+#   mqttInstance = nothing
+#   attempt = 0
+#   starttime = Dates.now()
+#   endtime = starttime + Second(connectiontimeout)
+#   errormsg = nothing
+#   while true
+#     timenow = Dates.now()
+#     timepass = timedifference(starttime, timenow, "seconds")
+#     timeleft = timedifference(timenow, endtime, "seconds")
 
-    if timepass <= connectiontimeout
-      attempt += 1
-      attempt > 1 ? println("Attempt $attempt to connect to MQTT broker. Timed out in $timeleft seconds. $errormsg") : nothing
+#     if timepass <= connectiontimeout
+#       attempt += 1
+#       attempt > 1 ? println("Attempt $attempt to connect to MQTT broker. Timed out in $timeleft seconds. $errormsg") : nothing
 
-      try
-        mqttInstance = mqttClientInstance_v2(
-          outgoingMsg[:msgMeta][:mqttBrokerAddress],
-          [mqttMsgReceiveTopic],
-          mqttMsgReceiveChannel,
-          keepaliveChannel,
-          onMsgCallback;
-          mqttBrokerPort=outgoingMsg[:msgMeta][:mqttBrokerPort],
-          clientId=senderId
-        )
-      break
-      catch e
-        errormsg = e
-        sleep(5)
-      end
-    else
-      println("Failed to instantiate MQTT client after $timepass seconds. $errormsg")
-      return nothing
-    end
-  end
+#       try
+#         mqttInstance = mqttClientInstance_v2(
+#           outgoingMsg[:msgMeta][:mqttBrokerAddress],
+#           [mqttMsgReceiveTopic],
+#           mqttMsgReceiveChannel,
+#           keepaliveChannel,
+#           onMsgCallback;
+#           mqttBrokerPort=outgoingMsg[:msgMeta][:mqttBrokerPort],
+#           clientId=senderId
+#         )
+#       break
+#       catch e
+#         errormsg = e
+#         sleep(5)
+#       end
+#     else
+#       println("Failed to instantiate MQTT client after $timepass seconds. $errormsg")
+#       return nothing
+#     end
+#   end
 
-  response = sendReceiveMqttMsg(mqttInstance, :ch1, outgoingMsg; 
-              responsetimeout=responsetimeout, responsemaxattempt=responsemaxattempt)
-  try disconnect(mqttInstance.client)  catch end
+#   response = sendReceiveMqttMsg(mqttInstance, :ch1, outgoingMsg; 
+#               responsetimeout=responsetimeout, responsemaxattempt=responsemaxattempt)
+#   try disconnect(mqttInstance.client)  catch end
 
-  return response
-end
-function sendReceiveMqttMsg(mqttInstance::mqttClientInstance_v2, receivechannel::Symbol,
-  outgoingMsg::Dict{Symbol, T}; responsetimeout::Integer=60, responsemaxattempt::Integer=1
-  )::NamedTuple where {T<:Any}
+#   return response
+# end
+# function sendReceiveMqttMsg(mqttInstance::mqttClientInstance_v2, receivechannel::Symbol,
+#   outgoingMsg::Dict{Symbol, T}; responsetimeout::Integer=60, responsemaxattempt::Integer=1
+#   )::NamedTuple where {T<:Any}
 
-  timepass = nothing
-  attempts = 1
-  while attempts <= responsemaxattempt
-    sendMqttMsg(mqttInstance, outgoingMsg)
+#   timepass = nothing
+#   attempts = 1
+#   while attempts <= responsemaxattempt
+#     sendMqttMsg(mqttInstance, outgoingMsg)
 
-    starttime = Dates.now()
-    while true 
-      timepass = timedifference(starttime, Dates.now(), "seconds")
+#     starttime = Dates.now()
+#     while true 
+#       timepass = timedifference(starttime, Dates.now(), "seconds")
 
-      if timepass <= responsetimeout
-        if isready(mqttInstance.msgReceiveChannel[receivechannel])
-          incomingMsg = take!(mqttInstance.msgReceiveChannel[receivechannel])
+#       if timepass <= responsetimeout
+#         if isready(mqttInstance.msgReceiveChannel[receivechannel])
+#           incomingMsg = take!(mqttInstance.msgReceiveChannel[receivechannel])
     
-          if incomingMsg[:msgMeta][:replyToMsgId] == outgoingMsg[:msgMeta][:msgId]
-            if incomingMsg[:msgMeta][:acknowledgestatus] == "NACK"
-              println("NACK")
-              break # resend the msg
-            else
-              return (success=true, error=nothing, response=incomingMsg[:payload])
-            end
-          end
-        end
-      else
-        break  
-      end
-      sleep(1)
-    end
-    if attempts > 1
-      println("\n<sendReceiveMqttMsg()> attempts $attempts/$responsemaxattempt ", @__FILE__, ":", @__LINE__, " $(Dates.now())")
-      pprintln(outgoingMsg)
-      println("</sendReceiveMqttMsg()> attempts $attempts/$responsemaxattempt  ", @__FILE__, ":", @__LINE__, " $(Dates.now())\n")
-      checkMqttConnection!(mqttInstance, keepaliveCheckInterval=5)
-    end
-    attempts += 1
-  end
+#           if incomingMsg[:msgMeta][:replyToMsgId] == outgoingMsg[:msgMeta][:msgId]
+#             if incomingMsg[:msgMeta][:acknowledgestatus] == "NACK"
+#               println("NACK")
+#               break # resend the msg
+#             else
+#               return (success=true, error=nothing, response=incomingMsg[:payload])
+#             end
+#           end
+#         end
+#       else
+#         break  
+#       end
+#       sleep(1)
+#     end
+#     if attempts > 1
+#       println("\n<sendReceiveMqttMsg()> attempts $attempts/$responsemaxattempt ", @__FILE__, ":", @__LINE__, " $(Dates.now())")
+#       pprintln(outgoingMsg)
+#       println("</sendReceiveMqttMsg()> attempts $attempts/$responsemaxattempt  ", @__FILE__, ":", @__LINE__, " $(Dates.now())\n")
+#       checkMqttConnection!(mqttInstance, keepaliveCheckInterval=5)
+#     end
+#     attempts += 1
+#   end
 
-  return (success=false, 
-          error="no response, timeout $timepass/$timeout, $(attempts-1) publish attempted", 
-          response=nothing)
-end
+#   return (success=false, 
+#           error="no response, timeout $timepass/$timeout, $(attempts-1) publish attempted", 
+#           response=nothing)
+# end
 
 
-""" Send a message to specified MQTT topic then wait for reply.
+# """ Send a message to specified MQTT topic then wait for reply.
 
-# Arguments
-  - `workDict::Dict`
-      A dictionary containing workspace data
-  - `incomingMsg::Dict`
-      The incoming message to process
+# # Arguments
+#   - `workDict::Dict`
+#       A dictionary containing workspace data
+#   - `incomingMsg::Dict`
+#       The incoming message to process
 
-# Keyword Arguments
-  - `data`
-      Optional data to be transferred. Default is nothing.
+# # Keyword Arguments
+#   - `data`
+#       Optional data to be transferred. Default is nothing.
 
-# Return
-  - `result::Dict`
-      A dictionary containing either:
-      - Metadata about the data transfer session if initiating a new transfer
-      - The requested data part if responding to a data part request
+# # Return
+#   - `result::Dict`
+#       A dictionary containing either:
+#       - Metadata about the data transfer session if initiating a new transfer
+#       - The requested data part if responding to a data part request
 
-# Example
-  ```jldoctest
-  julia> using Revise
-  julia> using GeneralUtils, Dates, JSON3, UUIDs
-  julia> msgMeta = GeneralUtils.generate_msgMeta(
-            "/testtopic",
-            senderName= "somename",
-            senderId= uuid4snakecase(),
-            mqttBrokerAddress= "test.mosquitto.org",
-            mqttBrokerPort= 1883,
-          )
-  julia> outgoingMsg = Dict(
-            :msgMeta=> msgMeta,
-            :payload=> Dict("hello"=> "World"),
-          )
-  julia> success, error = GeneralUtils.sendMqttMsg(outgoingMsg)
-  ```
-# TODO
-  - [x] transfer multiple msg with the same mqtt connection. The transfer loop should be 
-        implemented by passing mqttInstance into sendReceiveMqttMsg() so that 
-        1-connection is used to send all data
-  - [] partsize should be calculate from the fact that MQTT max size is 4MB (256MB theorectically)
+# # Example
+#   ```jldoctest
+#   julia> using Revise
+#   julia> using GeneralUtils, Dates, JSON3, UUIDs
+#   julia> msgMeta = GeneralUtils.generate_msgMeta(
+#             "/testtopic",
+#             senderName= "somename",
+#             senderId= uuid4snakecase(),
+#             mqttBrokerAddress= "test.mosquitto.org",
+#             mqttBrokerPort= 1883,
+#           )
+#   julia> outgoingMsg = Dict(
+#             :msgMeta=> msgMeta,
+#             :payload=> Dict("hello"=> "World"),
+#           )
+#   julia> success, error = GeneralUtils.sendMqttMsg(outgoingMsg)
+#   ```
+# # TODO
+#   - [x] transfer multiple msg with the same mqtt connection. The transfer loop should be 
+#         implemented by passing mqttInstance into sendReceiveMqttMsg() so that 
+#         1-connection is used to send all data
+#   - [] partsize should be calculate from the fact that MQTT max size is 4MB (256MB theorectically)
 
-# Signature
-"""
-function dataTransferOverMQTT_sender(workDict::Dict, incomingMsg::Dict; data=nothing)
-  dataTransferSessionID = nothing
+# # Signature
+# """
+# function dataTransferOverMQTT_sender(workDict::Dict, incomingMsg::Dict; data=nothing)
+#   dataTransferSessionID = nothing
 
-  if !haskey(incomingMsg[:payload], :dataTransferSessionID)
-    """ Expected incomingMsg (without "dataTransferSessionID") for requesting metadata
+#   if !haskey(incomingMsg[:payload], :dataTransferSessionID)
+#     """ Expected incomingMsg (without "dataTransferSessionID") for requesting metadata
     
-    Dict(:payload => Dict(:args => Dict(), :functioncall => "load_winetable"),
-     :msgMeta => Dict(:msgPurpose => nothing,
-                      :receiverId => nothing,
-                      :getpost => nothing,
-                      :msgId => "7fe4b765_fa2e_4c2e_9df0_9cb97e84ec32",
-                      :requestresponse => nothing,
-                      :msgFormatVersion => nothing,
-                      :timestamp => "Tue Oct 01 2024 16:22:12 GMT+0700 (เวลาอินโดจีน)",
-                      :replyToMsgId => nothing,
-                      :acknowledgestatus => nothing,
-                      :sendTo => "/yiem_branch_1/agent/wine/backend/db/api/v1/testing",
-                      :mqttBrokerPort => nothing,
-                      :receiverName => "agent_wine_backend",
-                      :replyTopic => "/agent/wine/frontend/514b634a_90b9_4e07_891d_fdf55b1aed25",
-                      :mqttBrokerAddress => "wss://mqtt.yiem.cc:8083",
-                      :senderName => "agent_wine_frontend",
-                      :senderselfnote => nothing,
-                      :senderId => "514b634a_90b9_4e07_891d_fdf55b1aed25"))
-    """
+#     Dict(:payload => Dict(:args => Dict(), :functioncall => "load_winetable"),
+#      :msgMeta => Dict(:msgPurpose => nothing,
+#                       :receiverId => nothing,
+#                       :getpost => nothing,
+#                       :msgId => "7fe4b765_fa2e_4c2e_9df0_9cb97e84ec32",
+#                       :requestresponse => nothing,
+#                       :msgFormatVersion => nothing,
+#                       :timestamp => "Tue Oct 01 2024 16:22:12 GMT+0700 (เวลาอินโดจีน)",
+#                       :replyToMsgId => nothing,
+#                       :acknowledgestatus => nothing,
+#                       :sendTo => "/yiem_branch_1/agent/wine/backend/db/api/v1/testing",
+#                       :mqttBrokerPort => nothing,
+#                       :receiverName => "agent_wine_backend",
+#                       :replyTopic => "/agent/wine/frontend/514b634a_90b9_4e07_891d_fdf55b1aed25",
+#                       :mqttBrokerAddress => "wss://mqtt.yiem.cc:8083",
+#                       :senderName => "agent_wine_frontend",
+#                       :senderselfnote => nothing,
+#                       :senderId => "514b634a_90b9_4e07_891d_fdf55b1aed25"))
+#     """
 
-    if data !== nothing # if the user provide data, store it in a new session workspace
-      dataTransferSessionID = uuid4snakecase()
-      haskey(workDict, :dataTransferOverMQTT) ? nothing : workDict[:dataTransferOverMQTT] = Dict()
-      workDict[:dataTransferOverMQTT][dataTransferSessionID] = Dict()
-      s = workDict[:dataTransferOverMQTT][dataTransferSessionID]
-      s[:dataTransferSessionID] = dataTransferSessionID
-      dataDict = Dict(pairs(data))
-      merge!(s, dataDict)
-    else
-      error("No data provided")
-    end
+#     if data !== nothing # if the user provide data, store it in a new session workspace
+#       dataTransferSessionID = uuid4snakecase()
+#       haskey(workDict, :dataTransferOverMQTT) ? nothing : workDict[:dataTransferOverMQTT] = Dict()
+#       workDict[:dataTransferOverMQTT][dataTransferSessionID] = Dict()
+#       s = workDict[:dataTransferOverMQTT][dataTransferSessionID]
+#       s[:dataTransferSessionID] = dataTransferSessionID
+#       dataDict = Dict(pairs(data))
+#       merge!(s, dataDict)
+#     else
+#       error("No data provided")
+#     end
 
-    # compute hash value for each piece of data
-    s = workDict[:dataTransferOverMQTT][dataTransferSessionID]
-    s[:hashes] = [bytes2hex(sha256(JSON3.write(s[:dataparts][i]))) for i in 1:s[:totalparts]]
+#     # compute hash value for each piece of data
+#     s = workDict[:dataTransferOverMQTT][dataTransferSessionID]
+#     s[:hashes] = [bytes2hex(sha256(JSON3.write(s[:dataparts][i]))) for i in 1:s[:totalparts]]
 
-    # send metadata without data to receiver()
-    datainfo = Dict()
-    for (k, v) in s
-      if k ∉ [:dataparts]
-        datainfo[k] = v
-      end
-    end
+#     # send metadata without data to receiver()
+#     datainfo = Dict()
+#     for (k, v) in s
+#       if k ∉ [:dataparts]
+#         datainfo[k] = v
+#       end
+#     end
 
-    d = Dict(
-      :result=> "dataTransferOverMQTT",
-      :dataTransferSessionID=> dataTransferSessionID,
-      Symbol(dataTransferSessionID)=> datainfo
-    )
+#     d = Dict(
+#       :result=> "dataTransferOverMQTT",
+#       :dataTransferSessionID=> dataTransferSessionID,
+#       Symbol(dataTransferSessionID)=> datainfo
+#     )
     
-    """ Sending metadata to the requester
-    Dict(:result => "dataTransferOverMQTT",
-     :b57123aa_a4c6_4d07_ace2_4885005d51c6 => Dict(:partsize => 3,
-                                                   :hashes => ["755fb25ae04890fa2a40c2b5fb5ddf05adeff6b934475998576bdf307359cd0f",
-                                                               "b95ba78344ad409755a386b6ab0cb2c8ea490756ce2df401aa6e5f77cf445025",
-                                                               "5b51277dd06ca255492cfc432824adf77e9e0de94179806cb130bef38e75da48"],
-                                                   :datatype => "vector{Dict}",
-                                                   :dataTransferSessionID => "b57123aa_a4c6_4d07_ace2_4885005d51c6",
-                                                   :totalparts => 46),
-     :dataTransferSessionID => "b57123aa_a4c6_4d07_ace2_4885005d51c6")
-    """
+#     """ Sending metadata to the requester
+#     Dict(:result => "dataTransferOverMQTT",
+#      :b57123aa_a4c6_4d07_ace2_4885005d51c6 => Dict(:partsize => 3,
+#                                                    :hashes => ["755fb25ae04890fa2a40c2b5fb5ddf05adeff6b934475998576bdf307359cd0f",
+#                                                                "b95ba78344ad409755a386b6ab0cb2c8ea490756ce2df401aa6e5f77cf445025",
+#                                                                "5b51277dd06ca255492cfc432824adf77e9e0de94179806cb130bef38e75da48"],
+#                                                    :datatype => "vector{Dict}",
+#                                                    :dataTransferSessionID => "b57123aa_a4c6_4d07_ace2_4885005d51c6",
+#                                                    :totalparts => 46),
+#      :dataTransferSessionID => "b57123aa_a4c6_4d07_ace2_4885005d51c6")
+#     """
 
-    return d
+#     return d
   
-  else
+#   else
 
-    """ Expected incomingMsg (with "dataTransferSessionID") for requesting a data part
-    Dict(:payload => Dict(:dataTransferSessionID => "5543f3b9_194e_4670_b961_e51c77955e40", :args => Dict(), :requestingDataPartNumber => 1, :functioncall => "load_winetable"),
-     :msgMeta => Dict(:msgPurpose => nothing,
-                      :receiverId => nothing,
-                      :getpost => nothing,
-                      :msgId => "fbcc3bd9_c2bc_4bde_908a_dfe88ab7a305",
-                      :requestresponse => nothing,
-                      :msgFormatVersion => nothing,
-                      :timestamp => "Tue Oct 01 2024 16:34:06 GMT+0700 (เวลาอินโดจีน)",
-                      :replyToMsgId => nothing,
-                      :acknowledgestatus => nothing,
-                      :sendTo => "/yiem_branch_1/agent/wine/backend/db/api/v1/testing",
-                      :mqttBrokerPort => nothing,
-                      :receiverName => "agent_wine_backend",
-                      :replyTopic => "/agent/wine/frontend/514b634a_90b9_4e07_891d_fdf55b1aed25",
-                      :mqttBrokerAddress => "wss://mqtt.yiem.cc:8083",
-                      :senderName => "agent_wine_frontend",
-                      :senderselfnote => nothing,
-                      :senderId => "514b634a_90b9_4e07_891d_fdf55b1aed25"))
-    """
+#     """ Expected incomingMsg (with "dataTransferSessionID") for requesting a data part
+#     Dict(:payload => Dict(:dataTransferSessionID => "5543f3b9_194e_4670_b961_e51c77955e40", :args => Dict(), :requestingDataPartNumber => 1, :functioncall => "load_winetable"),
+#      :msgMeta => Dict(:msgPurpose => nothing,
+#                       :receiverId => nothing,
+#                       :getpost => nothing,
+#                       :msgId => "fbcc3bd9_c2bc_4bde_908a_dfe88ab7a305",
+#                       :requestresponse => nothing,
+#                       :msgFormatVersion => nothing,
+#                       :timestamp => "Tue Oct 01 2024 16:34:06 GMT+0700 (เวลาอินโดจีน)",
+#                       :replyToMsgId => nothing,
+#                       :acknowledgestatus => nothing,
+#                       :sendTo => "/yiem_branch_1/agent/wine/backend/db/api/v1/testing",
+#                       :mqttBrokerPort => nothing,
+#                       :receiverName => "agent_wine_backend",
+#                       :replyTopic => "/agent/wine/frontend/514b634a_90b9_4e07_891d_fdf55b1aed25",
+#                       :mqttBrokerAddress => "wss://mqtt.yiem.cc:8083",
+#                       :senderName => "agent_wine_frontend",
+#                       :senderselfnote => nothing,
+#                       :senderId => "514b634a_90b9_4e07_891d_fdf55b1aed25"))
+#     """
     
-    # check transfer session id
-    dataTransferSessionID = incomingMsg[:payload][:dataTransferSessionID]
-    clientRequestingDataPartNumber = 
-        incomingMsg[:payload][:requestingDataPartNumber]
-    s = workDict[:dataTransferOverMQTT][dataTransferSessionID]
+#     # check transfer session id
+#     dataTransferSessionID = incomingMsg[:payload][:dataTransferSessionID]
+#     clientRequestingDataPartNumber = 
+#         incomingMsg[:payload][:requestingDataPartNumber]
+#     s = workDict[:dataTransferOverMQTT][dataTransferSessionID]
 
-    d = Dict(
-      :result=> "dataTransferOverMQTT",
-      :dataTransferSessionID=> dataTransferSessionID,
-      Symbol(dataTransferSessionID)=> Dict(
-        :dataPartNumber=> clientRequestingDataPartNumber, 
-        :datapart=> s[:dataparts][clientRequestingDataPartNumber]
-        ),
-      )
+#     d = Dict(
+#       :result=> "dataTransferOverMQTT",
+#       :dataTransferSessionID=> dataTransferSessionID,
+#       Symbol(dataTransferSessionID)=> Dict(
+#         :dataPartNumber=> clientRequestingDataPartNumber, 
+#         :datapart=> s[:dataparts][clientRequestingDataPartNumber]
+#         ),
+#       )
 
-    return d
-  end
-end
+#     return d
+#   end
+# end
 
-""" Send a message to specified MQTT topic then wait for reply.
+# """ Send a message to specified MQTT topic then wait for reply.
 
-# Arguments
-  - `outgoingMsg::Dict`
-      an outgoing message
+# # Arguments
+#   - `outgoingMsg::Dict`
+#       an outgoing message
 
-# Return
-  - `result::NamedTuple`
-    ( success= true, error= nothing )
+# # Return
+#   - `result::NamedTuple`
+#     ( success= true, error= nothing )
 
-# Example
-  ```jldoctest
-  julia> using Revise
-  julia> using GeneralUtils, Dates, JSON3, UUIDs
-  julia> msgMeta = GeneralUtils.generate_msgMeta(
-            "/testtopic",
-            senderName= "somename",
-            senderId= uuid4snakecase(),
-            mqttBrokerAddress= "test.mosquitto.org",
-            mqttBrokerPort= 1883,
-          )
-  julia> outgoingMsg = Dict(
-            :msgMeta=> msgMeta,
-            :payload=> Dict("hello"=> "World"),
-          )
-  julia> success, error = GeneralUtils.sendMqttMsg(outgoingMsg)
-  ```
-# TODO
-  - [PENDING]
+# # Example
+#   ```jldoctest
+#   julia> using Revise
+#   julia> using GeneralUtils, Dates, JSON3, UUIDs
+#   julia> msgMeta = GeneralUtils.generate_msgMeta(
+#             "/testtopic",
+#             senderName= "somename",
+#             senderId= uuid4snakecase(),
+#             mqttBrokerAddress= "test.mosquitto.org",
+#             mqttBrokerPort= 1883,
+#           )
+#   julia> outgoingMsg = Dict(
+#             :msgMeta=> msgMeta,
+#             :payload=> Dict("hello"=> "World"),
+#           )
+#   julia> success, error = GeneralUtils.sendMqttMsg(outgoingMsg)
+#   ```
+# # TODO
+#   - [PENDING]
 
-# Signature
-"""
-function dataTransferOverMQTT_receiver()
+# # Signature
+# """
+# function dataTransferOverMQTT_receiver()
   
 
 
@@ -878,7 +879,7 @@ function dataTransferOverMQTT_receiver()
 
 
 
-end
+# end
 
 
 
diff --git a/src/dbUtil.jl b/src/dbUtil.jl
index 40296bd..2e4fea8 100644
--- a/src/dbUtil.jl
+++ b/src/dbUtil.jl
@@ -2,7 +2,7 @@ module dbUtil
   
 export dictToPostgresKeyValueString, generateInsertSQL, generateUpdateSQL
 
-using JSON3, DataStructures, Distributions, Random, Dates, UUIDs, MQTTClient, DataFrames,
+using JSON3, DataStructures, Distributions, Random, Dates, UUIDs, DataFrames,
       SHA
 using ..util
 
diff --git a/src/interface.jl b/src/interface.jl
index f7c5672..dea5dcb 100644
--- a/src/interface.jl
+++ b/src/interface.jl
@@ -8,7 +8,7 @@ export noNegative!, randomWithProb, randomChoiceWithProb, findIndex, limitvalue,
         isLess, allTrue, getStringBetweenCharacters, JSON3read_stringKey, mkDictPath!, 
         getDictPath, detectKeywordVariation, textToDict
 
-using JSON3, DataStructures, Distributions, Random, Dates, UUIDs, MQTTClient, DataFrames, CSV
+using JSON3, DataStructures, Distributions, Random, Dates, UUIDs, DataFrames, CSV
 using ..util, ..communication
 
 # ---------------------------------------------- 100 --------------------------------------------- #
diff --git a/src/util.jl b/src/util.jl
index 16ca962..671a201 100644
--- a/src/util.jl
+++ b/src/util.jl
@@ -9,7 +9,7 @@ export timedifference, showstracktrace, findHighestIndexKey, uuid4snakecase, rep
         extractTextBetweenCharacter, extractTextBetweenString, 
         convertCamelSnakeKebabCase, fitrange, recentElementsIndex, nonRecentElementsIndex
 
-using JSON3, DataStructures, Distributions, Random, Dates, UUIDs, MQTTClient, DataFrames
+using JSON3, DataStructures, Distributions, Random, Dates, UUIDs, DataFrames
 
 # ---------------------------------------------- 100 --------------------------------------------- #