How to use WebRTC without an answer?

Question

In the absence of a signalling server for coordinating the initial exchange, does WebRTC provide any way to allow the responder to send information freely to the caller, if the responder has only received an offer and has no other methods of communication with the caller?

(There's no signalling server because the web app must be useable offline. Any method to establish a connection with only one exchange of information would also be useful.)

_{Sorry, it's a long and weird question.}

score 1 · Answer 1 · answered Sep 23 '16 at 07:22

1

I guess by offline you mean that you have two parties that will connect through a network not connected to the internet.

Signaling is just a way to transmit information between the two parties. For the sake of example it can even be manual copy and paste. Even one of the parties can play the role of a server if the other one has a way of connecting to it (doable within the same network).

Without some kind of signaling mechanism, a WebRTC connection is not possible. And signaling is not part of the WebRTC specification, nor of any implementation.

answered Sep 23 '16 at 07:22

Adrian Ber

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Sorry, to clarify, I have a kind-of signalling mechanism, but only the caller can use it. The responder can only read it, so it only works one way. – Shien Sep 23 '16 at 08:55
Then unfortunately you cannot establish a WebRTC connection. – Adrian Ber Sep 23 '16 at 12:58
I am also confused by this. Once the originator gets its ICE candidate, that is everything necessary for sending data to them. What is the purpose of the peer needing to send an answer out-of-band back to them instead of just sending messages? – Charles Lohr Aug 16 '22 at 07:27
I guess it's to check both way communication. – Adrian Ber Aug 16 '22 at 12:23

score 0 · Accepted Answer · answered Sep 23 '16 at 16:41

Webrtc needs a signalling system for establishing peer to peer connection. Now the thing to notice is why it needs signalling.

In the process of establishing peer connection the two parties exchange sdp which contains information such as the IP and Port at both ends at which the media/data packets will get exchanged. Similarly it contains the encoding/decoding or codec to be used plus many other useful things.Thus without the exchange of these packets between both the parties any communication can't be possible.

That is why it is not possible at least in case of webrtc that without the communication from both sides a peer connection can be established.

How to use WebRTC without an answer?

2 Answers2