Imprevement to 'Emulated POSIX TCP Sockets over WebSockets' to work with Socks4/5 proxy .

[Maksons]

Hello to all,

Would like to share idea of adding connection pass to Socks 4 or 5 proxy.
It's look like should not be hard, just on first message add extra header with destination IP/Port/protocol and on response to check connection result (connected/bindded) and then report status on POSIX socket.
On PC side same 'websockify' + Socks proxy.
It will give option to connect/listen for multiple emulated sockets in web application not single one.

[Maksons]

In any case, I have implemented this feature in Emscripten (with help from Gemini) and :

• it's possible to connect to any IP / address over emulated POSIX sockets
• on PC side Websockify should be directed to Socks5 proxy , or I have new Python script which serve WebSocket Socks5 Proxy solution.
• I tested it by connecting to PostgreSQL
• I use WEBSOCKET_SUBPROTOCOL='binary,socks5' at compilation time to use new realization.
• Websockify+Socks5 handle only TCP , but new created Python script planed to support UDP as well (currently improving it).

Any advice are welcome.
If anyone interested could share code / patch.
If maintainers are interested to include this feature to Emscripten, I'm ready to prepare Pull request.