libdatachannel: PeerConnection sometimes fails to establish local connection

Hi Paul-Louis,

I hope you are well 😃

I’m using libdatachannel to facilitate networking in a realtime multiplayer game. When a player hosts a game they run both the client & server code within the same process & thread i.e. the architecture is client-server, the host just happens to be running both the client & server code. In this hosting instance two rtc::PeerConnections are created, one for the “server side” code & one for the “client side” code. I then connect these two local PeerConnections to eachother. Remotely connecting clients only create a single rtc::PeerConnection that is connected to the host’s server side rtc::PeerConnection.

Now I’m occasionally having trouble establishing a connection between the host’s two local rtc::PeerConnection’s in the same process. I’d say connection establishment fails 5% of the time. As a side note I have a WebAssembly build of the game and I don’t experience the same issue.

I’ve attached game.log captured during a session that experienced the problem. It’s sprinkled with a few of my own log items for my own context so I can help but I can remove these if you like. I’ve also attached my stun_server.log although it’s likely of little use other than for my own context.

Interestingly in the captured logs the client side rtc::PeerConnection finds both host & srflx ice candidates, but the server side only finds a host candidate. Seems a little strange to me. My STUN server also sees much more activity in these 5% failure cases vs the 95% happy path cases. After 10 seconds (at the end of the logs) the game aborts the connection attempt.

Let me know how I can help?

Kind regards,

Deon