Hello!
From what I understand, WebSockets (as opposed to plain TCP/IP) proxy will be suitable for you. WebSockets is supported in modern browsers, and there is a Flash implementation of WebSockets for those ones which don't.
I can write an asynchronous application (using libuv) or a multithreaded one.
I can mostly work only on weekends, that's why such term. However, it has been often the case I was able to be done earlier than planned.