Yup, it's been a while since I read the spec but I believe it leaves the transport up to what can be negotiated for maximum compatibility.

If you handle the SDP and SCTP handshake you can force it to only use UDP via SCTP. Chrome and FF both support it today.

Yeah with WebRTC data channels can be UDP!

It's just -- and this may be mildly out of date -- EXTREMELY hard to find a server-side setup that will let you do all of what the browsers now support with WebRTC.

My recollection from the last time I skipped across this topic was: there are 1 or 2 heavyweight open source projects that mostly focus on the video aspects but also supported data channel stuff, and then one lightweight C and one lightweight Go project that supported everything, and you were mostly out of luck otherwise.

I remember the last time I checked, a year ago or so, pieces of what's required being worked on in recent OTP releases in BEAM-land. Hmmm ... time to check again.

There is no raw udp or tcp access from browser js, just higher lwvel protocols that are implemented over tcp or udp.