Support Unix Domain Sockets

[rafael-biz]

Describe the feature request

I'm am trying to connect a client application to a MQTT message broker (Mosquitto) through Unix Domain Sockets instead of the localhost loopback address (both are installed on the same machine). However, I'm using the MqttClient and its current implementation doesn't seem to support it.

Which project is your feature request related to?

• Client

Describe the solution you'd like

I would like the ability to specify the unix file name as a parameter at the MqttClientOptionsBuilder.

Example

    MqttClientOptions clientOptions = new MqttClientOptionsBuilder()
        .WithUnixDomainSocket("foo.socket")
        .Build();

[chkr1011]

These are not yet support and require a rework of the internal socket handling because it requires usage of different classes, overloads etc. I will have a look on how to implement it.

[chkr1011]

@rafael-biz Please download the following build from the myget feed: https://www.myget.org/feed/mqttnet/package/nuget/MQTTnet/4.3.3.957

This versions adds a new overload for the client options builder (WithEndPoint). It allows you to pass another end point implementation type like the unis domain sockets.

I am not sure if you also have to change the AddressFamily in the options but it may be required.

Please test the version and let me know if it works.

[rafael-biz]

@chkr1011 Unfortunately I can't test it now because I just discovered that Mosquitto's Unix Domain Sockets support on Windows isn't working either.
eclipse-mosquitto/mosquitto#2857

I'll wait for a fix in Mosquitto so I can test MQTTNet.

Thank you very much!

[chkr1011]

OK, I will then merge the PR because it exposes the EndPoint which allows using other types of endpoints.