B4J Question Irregular characters when sending via MQTT

[warayTek]

Hi everyone, I am trying to test the MQTT chat app. When I try to send a string I have the following output.
Using B4J

Public Sub SendMessage(Body As String)
    If connected Then
        Log(Body)
        client.Publish2("home/light/livingRm", CreateMessage(Body), 0, False)
    End If
End Sub

Output from Ubuntu Terminal(broker side)

But when using MQTT explorer app, it sends okay.

Thanks for any input.

 

[DonManfred]

Are you sending serialized data? What does createMessage do?

Note

The messages are serialized with B4XSerializator (RandomAccessFile library). B4XSerializator is very useful for cross platform communication.

if you are using this example

[B4X] MQTT Chat Room

It's time to learn how to use MQTT: https://www.b4x.com/android/forum/threads/59471/#content It is simple and powerful. In most cases MQTT is the best solution for low level networks. Low level network means a network solution that is traditionally based on ServerSocket + Socket + AsyncStreams...

www.b4x.com

Note that it should work in all B4X projects.

The serialized data are not meant to print in serverside...

 

[warayTek]

Are you sending serialized data? What does createMessage do?

Note


if you are using this example

[B4X] MQTT Chat Room

It's time to learn how to use MQTT: https://www.b4x.com/android/forum/threads/59471/#content It is simple and powerful. In most cases MQTT is the best solution for low level networks. Low level network means a network solution that is traditionally based on ServerSocket + Socket + AsyncStreams...

www.b4x.com

Note that it should work in all B4X projects.

The serialized data are not meant to print in serverside...

Thanks for the time. I got it working.

 

[DonManfred]

I got it working.

what did you change?

 

[warayTek]

Temporarily commented this line.
"serializator.ConvertBytesToObject()"

And to send a test message use the
client.Publish("home/light/livingRm","Hello from B4J".GetBytes("UTF8"))

I have another question, how to receive the message in B4J?
This the command I use in the terminal (broker side) mosquitto_pub -h 192.168.1.44 -t home/light/livingRm -m "Hello earthling."

 

[DonManfred]

I have another question, how to receive the message in B4J?

run a MQTT-Client in B4J and subscribe to home/light/livingRm

BTW: The B4J-client is able to work with the serialized-data.

 

[warayTek]

run a MQTT-Client in B4J and subscribe to home/light/livingRm

BTW: The B4J-client is able to work work the serialized-data.

"BTW: The B4J-client is able to work work the serialized-data." okay I will try it.

it gives an error when it receives the message.

Private Sub client_MessageArrived (Topic As String,Payload As String)
Log(Topic)
End Sub

here is the error

Connected: true
1
java.lang.Exception: Sub client_messagearrived signature does not match expected signature.
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:113)
    at anywheresoftware.b4a.BA$3.run(BA.java:267)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:428)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:427)
    at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:174)
    at java.base/java.lang.Thread.run(Thread.java:834)

 

[DonManfred]

it gives an error when it receives the message.

check the b4j-client-example

this is how the code should look like

Private Sub client_MessageArrived (Topic As String, Payload() As Byte)
    Dim receivedObject As Object = serializator.ConvertBytesToObject(Payload)
    If Topic = "all/connect" Or Topic = "all/disconnect" Then
        'new client has connected or disconnected
        'do nothing. The server will handle it.
    Else if Topic = "all/users" Then
        Dim newUsers As List = receivedObject
        Main.NewUsers(newUsers)
    Else
        Dim m As Message = receivedObject
        Main.NewMessage(m)
    End If
       
End Sub

This expects to get the payload as serialized though ;-)