Make server respond to websocket ping messages

[maximbaz]

Webapp sends 'Wire is so much nicer with internet!' every now and then to make sure it is still able to talk to the server. However because server doesn't respond to this message, in some cases it is impossible to detect if webapp is actually offline.

See this message for details: wireapp/wire-desktop#1129 (comment)

Please make Wire respond with some string like 'Indeed it is' on each such ping request, so that it's possible to improve webapp.

[tiago-loureiro]

Hi @maximbaz

Websockets have a built-in mechanism for this using control frames which is already supported on the backend (check this)

@bennyn Perhaps you want to have a look at this?

[maximbaz]

Hey hey @tiago-loureiro 👋

Yes I know about those, unfortunately they are not supported by client-side javascript, that's the reason webapp is faking ping requests by sending strings to the server.

https://www.w3.org/TR/websockets/#ping-and-pong-frames

The WebSocket protocol specification defines Ping and Pong frames that can be used for keep-alive, heart-beats, network status probing, latency instrumentation, and so forth. These are not currently exposed in the API.

[fisx]

Working on it. Thanks @maximbaz for reporting this, and for not letting go! :-)

[fisx]

I just talked with @bennyn:

• yes, the browser gives js no chance of learning about the death of its websocket other than the payload-level ping/pong game.
• we don't want to use protobuf to implement this like with all the other websocket traffic. the backend dislikes the beaurocracy involved, and the web client would have to pay a performance penalty.
• instead, the message payloads are ping and pong (those 4 bytes).
• all messages other than ping sent by the client will be ignored as before. this guarantees backwards compatibility (currently, the web client never sends ping).
• this plan needs to be confirmed by the other clients.

[maximbaz]

Solid plan 👍 Thank you both!

[marcoconti83]

To my understanding, this is an optional addition to the protocol. Only if a client sends a ping, the backend will respond with a pong. Currently no clients sends a ping so this addition is safe for older clients.

[maximbaz]

Yay for getting this merged! 🙂 @bennyn ping me if you want an early testing, or even for implementation if you guys are busy with other stuff, this is my most annoying issue with Wire on Desktop so I would be more than happy to collaborate again and get this implemented quickly 😉

[bennycode]

@maximbaz PRs are more than welcome because we won't have time this month to implement it ourselves.

[fisx]

@maximbaz also note that the PR went to staging yesterday; the next release that will bring it to app.wire.com is still a few days off (not scheduled, in fact, but very likely due this month).

btw i really appreciate your patience and helpful attitude. it's great working with you! :-)

[maximbaz]

Thanks for the kind words, happy to collaborate with you too 🙂 I have some preliminary implementation, please ping me when the code reaches app.wire.com so I can do some final testing before submitting a PR.

[fisx]

@maximbaz now this ticket is legitimately closed, and #561 is in production.

please re-open (or ping me) if you need anything else from the backend.