Add support for Socket.IO v2.x

[armoha]

... and therefore revision 4 of Socket.IO protocol and revision 3 of Engine.IO protocol, behind feature gate I suppose.
The v3 server can communicate with v2 clients, but v3 client can't connect to a v2 server.

I'm still learning Rust and Socket.IO but I'd like to contribute if this seems good first issue,

• Revision 4 Socket.IO protocol: https://github.com/socketio/socket.io-protocol/tree/v4

[1c3t3a]

Yeah makes sense! I appreciate every contribution :) You can basically fully lean on the current implementation and try to retrofit the changes made to the protocol. A feature flag definitely makes sense, especially regarding the switch in ping and pong packets. As there are currently ongoing changes to the crate, it might make sense to sync with @nshaaban-cPacket on when and how it would make sense to implement this. When you run into questions don't hesitate to ask, I am happy to help!

[ctrlaltf24]

main is available to any and all contributions! No synchronization needed, happy to answer questions/point you in the right direction though. As for how to implement this, feature flag make sense (will require some changes to CI), as well as try to keep all the protocol specific logic in one (or a couple) places so we're not stepping on each other's toes and accidentally break each other's code.

I'm still learning Rust

No issues at all, we're all still learning! Always learning! FYI, I've setup a VSCode devcontainer for Socket.IO, if you use VSCode + Docker, it can setup all the project dependencies and CI with a couple clicks.

[RyanWongGithub]

I'm glad the author can help, I would like to know how to modify this existing code to support engin protocol 3? @1c3t3a