B4R Question mqtt Client Id encoding

fbritop · Feb 21, 2022

I'm using a simple MQTT init. I want to send as the clientId the Mac Address of an ESP32.

B4X:

mqtt.Initialize2(wifiSocket.Stream, "api.***.com", 82, bc.HexFromBytes(MacAddress), "mqtt_MessageArrived", "mqtt_Disconnected")"]

Sub MacAddress() As Byte()
    RunNative("getMac", Null)
    Return MacArray
End Sub

#if C
  void getMac(B4R::Object* u) {
  WiFi.macAddress((Byte*)b4r_main::_macarray->data);
  }
#end if

I cannot find the way that the clientId is sent as plain text. On the other end, I have mosca mqtt broker, that when the client connects it just gives me a strange encoding for the client Id

Is this a problem with the client or the broker?

Erel · Feb 22, 2022

Does it look ok if you send a constant string: "test12" ?

fbritop · Feb 22, 2022

Yes it send it correctly when using constants

Erel · Feb 22, 2022

It happens because bc.HexFromBytes creates the string on the stack.

The fact that we need a string here makes it more complicated.
This should work (I haven't tested it with MQTT):

B4X:

Sub Process_Globals
    Public Serial1 As Serial
    Private MacArray(6) As Byte
    Private MacHexBytes(13) As Byte
    Private MacString As String
    
End Sub

Private Sub AppStart
    Serial1.Initialize(115200)
    Log("AppStart")
    RunNative("getMac", Null)
    Dim bc As ByteConverter
    Dim b() As Byte = bc.HexFromBytes(MacArray)
    bc.ArrayCopy2(b, 0, MacHexBytes, 0, 12) 'byte 13 = 0
    RunNative("UpdateStringDataPointer", Null)
    Log(MacString)
End Sub


#if C
 void getMac(B4R::Object* u) {
      WiFi.macAddress((Byte*)b4r_main::_macarray->data);
    ((Byte*)b4r_main::_macarray->data)[6] = 0;
    
}
void UpdateStringDataPointer(B4R::Object* u) {
    b4r_main::_macstring->data = (const char*)b4r_main::_machexbytes->data;
}
#end if

B4R Question mqtt Client Id encoding

fbritop

Well-Known Member

Erel

B4X founder

fbritop

Well-Known Member

Erel

B4X founder

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B4R Question mqtt Client Id encoding

fbritop

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Erel

B4X founder

fbritop

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Erel

B4X founder

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