Hello
I am struggling to understand how to use the lastwill message system in mqtt.
I believe that the lastwill message work like this:
'
If we have a topic:
-and clientA subscribed to this topic:
-and clientB is connected with a desire for a LastWill like this:
-and you end clientB like this:
Then the event for clientA will be fired.
But I can't get this to work. Can someone help me. I've made a short B4X project showing that the clientA_MessageArrived is not fired for TopicClientBWill. The code in the project and log is shown below. The project is also attached.
Can someone help me?
And this is the log when the button is pushed:
The log shows that clientA_MessageArrived was not fired with subject ClientBWill after clientB was disconnected.
I am struggling to understand how to use the lastwill message system in mqtt.
I believe that the lastwill message work like this:
'
If we have a topic:
-and clientA subscribed to this topic:
-and clientB is connected with a desire for a LastWill like this:
-and you end clientB like this:
Then the event for clientA will be fired.
But I can't get this to work. Can someone help me. I've made a short B4X project showing that the clientA_MessageArrived is not fired for TopicClientBWill. The code in the project and log is shown below. The project is also attached.
Can someone help me?
B4X:
#Region Shared Files
#CustomBuildAction: folders ready, %WINDIR%\System32\Robocopy.exe,"..\..\Shared Files" "..\Files"
'Ctrl + click to sync files: ide://run?file=%WINDIR%\System32\Robocopy.exe&args=..\..\Shared+Files&args=..\Files&FilesSync=True
#End Region
'Ctrl + click to export as zip: ide://run?File=%B4X%\Zipper.jar&Args=Project.zip
Sub Class_Globals
Private Root As B4XView
Private xui As XUI
Private MqttBroker As MqttBroker
Private clientA As MqttClient
Private clientB As MqttClient
Private bc As ByteConverter
End Sub
Public Sub Initialize
' B4XPages.GetManager.LogEvents = True
End Sub
'This event will be called once, before the page becomes visible.
Private Sub B4XPage_Created (Root1 As B4XView)
Root = Root1
Root.LoadLayout("MainPage")
End Sub
'You can see the list of page related events in the B4XPagesManager object. The event name is B4XPage.
Private Sub Button1_Click
Dim TopicClientBWill As String = "ClientBWill"
Dim PayloadClientBWill() As Byte = "Stoped".GetBytes("AscII")
Dim TopicCLientBStarted As String = "ClientBStarted"
Dim PayloadClientBStarted() As Byte = "Started".GetBytes("AscII")
Dim BrokerURI As String = "tcp://localhost:1883"
MqttBroker.Initialize("broker",1883)
MqttBroker.DebugLog = False
MqttBroker.Start
Log("ClientA Connect to broker")
clientA.Initialize("clientA",BrokerURI,"clientA")
clientA.Connect
Wait For clientA_Connected (Success As Boolean)
Log($"clientA_Connected(${Success})"$)
clientA.Subscribe(TopicCLientBStarted,1)
clientA.Subscribe(TopicClientBWill,1)
clientB.Initialize("clientB",BrokerURI,"clientB")
Dim options As MqttConnectOptions
options.Initialize("","")
options.SetLastWill(TopicClientBWill,PayloadClientBWill,1,True)
clientB.Connect2(options)
Wait For clientB_Connected (Success As Boolean)
Log($"clientB_Connected(${Success})"$)
clientB.Publish2(TopicCLientBStarted,PayloadClientBStarted,1,True)
Sleep(5000)
clientB.Close
Wait For clientB_Disconnected
Log("clientB_Disconnected")
End Sub
Private Sub clientA_MessageArrived (Topic As String, Payload() As Byte)
Dim bc As ByteConverter
Log($"clientA_MessageArrived Topic:${Topic} Payload:${bc.StringFromBytes(Payload,"AscII")}"$)
End SubAnd this is the log when the button is pushed:
The log shows that clientA_MessageArrived was not fired with subject ClientBWill after clientB was disconnected.
Last edited:
