Unable to connect with Unix Socket

[BastienCUENOT]

Unable to connect with Unix Socket

[chkr1011]

I cannot this test on my own because I have no Unix socket server.

I searched for some examples and in those examples, they set the protocol type to IP instead of TCP.
So, I exposed the protocol type in the MQTTnet client options.

Could you please try version 4.3.4.1071 from the MyGet feed (https://www.myget.org/feed/mqttnet/package/nuget/MQTTnet) and let me know if changing the protocol type (to IP) fixes the issue?

[BastienCUENOT]

I try to set protocol type to "IP" with the build 4.3.4.1071.
My code:

mqttClient = this.mqttFactory.CreateMqttClient();
var mqttClientOptions = new MqttClientOptions
{
  ChannelOptions = new MqttClientTcpOptions
  {
    RemoteEndpoint = new UnixDomainSocketEndPoint("/tmp/mosquitto.sock"),
    AddressFamily = AddressFamily.Unix,
    ProtocolType = ProtocolType.IP
  },
};
var response = await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
if (response.ResultCode == MqttClientConnectResultCode.Success)
{
    Console.Write("CONNECTED TO MQTT BROKER !");
}

I don't have the same error but there is another one on the NoDelay property:

Unhandled exception. MQTTnet.Exceptions.MqttCommunicationException: Operation not supported
May 13 08:31:23 PWE HmiAPI[167]:  ---> System.Net.Sockets.SocketException (95): Operation not supported
May 13 08:31:23 PWE HmiAPI[167]:    at System.Net.Sockets.Socket.UpdateStatusAfterSocketErrorAndThrowException(SocketError error, Boolean disconnectOnFailure, String callerName)
May 13 08:31:23 PWE HmiAPI[167]:    at System.Net.Sockets.Socket.UpdateStatusAfterSocketOptionErrorAndThrowException(SocketError error, String callerName)
May 13 08:31:23 PWE HmiAPI[167]:    at System.Net.Sockets.Socket.SetSocketOption(SocketOptionLevel optionLevel, SocketOptionName optionName, Int32 optionValue, Boolean silent)
May 13 08:31:23 PWE HmiAPI[167]:    at System.Net.Sockets.Socket.SetSocketOption(SocketOptionLevel optionLevel, SocketOptionName optionName, Int32 optionValue)
May 13 08:31:23 PWE HmiAPI[167]:    at MQTTnet.Implementations.CrossPlatformSocket.set_NoDelay(Boolean value)
May 13 08:31:23 PWE HmiAPI[167]:    at MQTTnet.Implementations.MqttTcpChannel.ConnectAsync(CancellationToken cancellationToken)
May 13 08:31:23 PWE HmiAPI[167]:    at MQTTnet.Adapter.MqttChannelAdapter.<>c__DisplayClass30_0.<<ConnectAsync>b__1>d.MoveNext()

I searched more information about SocketOptionLevel, and it seems that it is not possible to set SocketOptionLevel.TCP or IP to an unix socket: https://learn.microsoft.com/en-us/dotnet/api/system.net.sockets.socketoptionlevel?view=net-8.0
(I use socket with "Unix" addressFamily).

---

Update:

I rebuild the library on my own, and I commented 'set' method for NoDelay property in the file 'CrossPlatformSocket.cs':

public bool NoDelay
{
    // We cannot use the _NoDelay_ property from the socket because there is an issue in .NET 4.5.2, 4.6.
    // The decompiled code is: this.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.Debug, value ? 1 : 0);
    // Which is wrong because the "NoDelay" should be set and not "Debug".
    get => false /*(int?)_socket.GetSocketOption(SocketOptionLevel.IP, SocketOptionName.NoDelay) != 0*/;
    set { } /* _socket.SetSocketOption(SocketOptionLevel.IP, SocketOptionName.NoDelay, value ? 1 : 0);*/
}

I know it is not a final solution, but it is only for testing.

Then, I set 'protocolType' to 'Unspecified' like that:

mqttClient = this.mqttFactory.CreateMqttClient();
var mqttClientOptions = new MqttClientOptions
{
  ChannelOptions = new MqttClientTcpOptions
  {
    RemoteEndpoint = new UnixDomainSocketEndPoint("/tmp/mosquitto.sock"),
    AddressFamily = AddressFamily.Unix,
    ProtocolType = ProtocolType.Unspecified
  },
};
var response = await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
if (response.ResultCode == MqttClientConnectResultCode.Success)
{
    Console.Write("CONNECTED TO MQTT BROKER !");
} 

With this change, it works !

[chkr1011]

Thanks for testing and providing feedback.

Please try again with version x.x.x.1073 from the myget feed. The NoDelay is only set if the protocol type supports that algorithm at all.

It if works I can create a PR, merge and release a new version.

[BastienCUENOT]

I tried with the build x.x.x.1073 and it works !
I think you can merge, and thank you for your support 😃