WebRTC TURN over TCP needs adjust

[scvthorsten]

Clients firewalls are outright configured to block UDP or not route UDP. This presents a problem to establish WebRTC sessions to our SipSorcery .NET backend, even when we provide a TURN server to proxy the traffic between peers. In this implementation, the browser is peer to the backend stack, the corresponding peer (on a static IP address)

While the client can establish a TCP connection to COTURN (our TURN server), it seems SipSorcery does not offer TCP options. It is not clear if this line L287 is a bug since "udp" is hard coded under the tcp condition:

sipsorcery/src/net/ICE/RTCIceCandidate.cs

Line 287 in 23441de

candidateStr = String.Format("{0} {1} udp {2} {3} {4} typ {5} tcptype {6} raddr {7} rport {8} generation 0",

[sipsorcery]

There is a TCP ICE channel albeit with a very confusing base class. I have personally never used or tested that implementation.

In the original implementation no TCP option was implemented for RTP as I was somewhat skeptical that it would work well enough to be useful. As soon as there's packet loss or congestion TCP is going to be a big handicap for real-time media. I do get the point about corporate firewalls blocking UDP and I guess with WebRTC now taking over from VoIP an occassionally glitchy stream is better than no stream.

[tozzi21]

WebRTC is indeed taking a learing role in the conversational AI implementations, since its ability to carry data and voice provides a cross-browser channel whilst avoiding WebSockets, often outright blocked in corporate networks.

We see tcp in the robust solutions like Google Meet, when udp failsover:

Engineers best to decide on their implementation. Quality difference in 1:1 streams should be minimally different (passing over same routes).

We shall do trails of PR #1295 in our preprod.

Really love your work. Will contribute additional PRs, wherever we can help too.

[bryanlimktscv]

@sipsorcery I saw that the PR #1295 is now merged, to align RTC candidate to use TCP. Can we release an updated Nuget with the changes?

[sipsorcery]

@bryanlimktscv (or anyone else) would you be able to confirm whether that PR allows ICE over TCP to now work?