Is In-Memory communication channels supported?

[mauroa]

The documentation mentions it: Extensible communication channels (e.g. In-Memory, TCP, TCP+TLS, WS), however I'm not sure if this is really supported and how I should configure it.

I ask this in order to avoid the firewall prompt to allow opening a TCP port when starting the MQTT server, in cases where the MQTT connection and messages exchange will be performed in-process.

Thanks

[wellsjiang]

I had this requirement a year ago, but after reviewing the documentation and issues, I found that MQTTnet does not provide a ready-to-use in-memory communication channel. It needs to be implemented manually. I’m not sure if this feature is available now. If it is still not provided, implementing this feature is quite easy. You just need to implement IMqttClientAdapterFactory, IMqttChannel, and IMqttServerAdapter.

[mauroa]

Thanks for your response. I did exactly that, since I noticed that it's not really supported. I have a working in-memory version now.
The trickiest part was to synchronize the memory stream of the channels to read/write correctly. Did you use another alternative than a MemoryStream to accomplish it?
Thanks

[sebastian-dev]

@mauroa
can you upload a small sample client/server with your implementaion.
have you benchmarked the connection: local TCP vs inMemmory.
Have you seen a significant improvement in performance or memory consumption?

[mauroa]

I'm attaching a simple console app that I made with the in-memory support. It uses MemoryStream and a series of thread synchronization and lock mechanisms to allow reading and writing correctly in both client and server sides, given the nature of the MemoryStream.

If you find improvements to make, please let me know.

TestMQTTnet.zip

[CZEMacLeod]

Would this be easier to implement using System.IO.Pipelines? - My understanding is it is designed for this kind or scenario.

[sebastian-dev]

As it is in the demo, you can only communicate within the application.
If you want to do this in memory between different applications, i.e. server <-> client, you have to do this via a global shared memory segment or via a named pipe.

[chkr1011]

The file Source/MQTTnet.Tests/Mockups/MemoryMqttChannel.cs contains an in-memory channel used for testing.
You can use it as a reference. An official in-memory channel is not part of this project.