Last Will not working?

[SCHoschY]

Describe your question

Im Currently testing LW and cant get it working.

Which project is your question related to?

• Client

Im currently testing with this example
I have extended the Optionsbuilder for credentials and last will. The credentials are working fine, but LW seems to not work.

        string topicLW = "test/LW";
        string messageLW = "Cya, im gone";

        ...
        var options = new MqttClientOptionsBuilder()
                          .WithClientId(clientId)
                          .WithTcpServer(broker, port)
                          .WithCredentials(username, password)
                          .WithCleanSession()
                          .WithKeepAlivePeriod(TimeSpan.FromSeconds(30)) 
                          //.WithWillDelayInterval(10) -> Im Using 3.1 - not implemented
                          .WithWillQualityOfServiceLevel(MqttQualityOfServiceLevel.AtLeastOnce)
                          .WithWillRetain(true)
                          .WithWillTopic(topicLW)
                          .WithWillPayload(messageLW)
                          .Build();

Am i missing a OptionsBuilder parameter or is something off in general?

---

The program sends 0-9 with these OptionsBuilder settings, but my "test/LW" topic does not get changed.

Im also Testing with Retained and clearing - noted here, to explain the 3rd screenshots with "missing" topic ;)

Initial Subscription

in the middle of my test-run:

10 min. after the test:

if i test it with another subscriber i get the same result:

run 1

schoschy@NB105:~$ mosquitto_sub -t test/LW -h 192.168.42.6

run 2 to verify that the normal messages do work

schoschy@NB105:~$ mosquitto_sub -t test/csharp -h 192.168.42.6
Hello, MQTT! Message number 0
Hello, MQTT! Message number 1
Hello, MQTT! Message number 2
Hello, MQTT! Message number 3
Hello, MQTT! Message number 4
Hello, MQTT! Message number 5
Hello, MQTT! Message number 6
Hello, MQTT! Message number 7
Hello, MQTT! Message number 8
Hello, MQTT! Message number 9

a Wireshark trace seems to be okay aswell.

Other applications of mine do offer a working LW retained message

schoschy@NB105:~$ mosquitto_sub -t Availability/Webio-20 -h 192.168.42.6 -v
Availability/Webio-20 Online
+pulled Eth Cable
Availability/Webio-20 Offline
+linked Eth Cable
Availability/Webio-20 Online

i did start a test-instance of mosquitto to check if there are problems with my Test-broker, that did also not help.

---

Thanks for your help and have a nice week

Schoschy

[chkr1011]

In the sample the client gets disconnected properly by calling DisconnectAsync. This will indicate a clean disconnect. The last will ist only published if the client is disconnected in a non clean way.

This means losing network connection or a crashing application. You can also try to make in non clean by avoiding the call of DisconnectAsync and instead calling Dispose. Or you simply close your application 😄

[SCHoschY]

I did test that behaviour and came to the same conclusion this weekend.

Working for years with MQTT applications that run 24/7 i never noticed that the LW is only triggered on an ungracefull disconnect, because i do only get those. :)

Thanks for the reminder!