PublishAsync does not fail when MQTTnet server is not running

I am using MQTTNet, a .NET library for MQTT based communication from below link

https://github.com/chkr1011/MQTTnet

I am using managed MQTT Client from below link

managed MQTT Client

https://github.com/chkr1011/MQTTnet/wiki/ManagedClient

I have below code to publish messages to MQTT server.

publish

MQTT server

var messagePayload = new MqttApplicationMessageBuilder()
.WithTopic("Topic1")
.WithPayload(message)
.WithExactlyOnceQoS()
.WithRetainFlag()
.Build();

try
{
await mqttClient.PublishAsync(messagePayload);
}
catch (Exception ex)
{
//Why I am not getting exception?
}


1 Answer
1

This behaviour by design of the MQTT Managed client. It uses an internal queue. All the messages published at added to this queue and are then sent to the server when it is available.
It also ensures that the messages are not lost and can be resent even if the application restarts. Quote from the project wiki.

All MQTT application messages are added to an internal queue and processed once the server is available.
All MQTT application messages can be stored to support sending them after a restart of the application

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