Websocket is actually not that complicated. A couple of headers to upgrade the request from HTTP to websocket, then framing of each payload.
But you could use something like websocketd, which spawns a process of your chioce for each client and pipes the websocket to stdin and vice versa.
https://github.com/joewalnes/websocketd
Each PHP process looks like it takes about 5 MB of ram on my laptop, so probably not the best method for 5000+ concurrent users if you use PHP, but still.
> I don't know of any library/framework that could help you with the websocket protocol level
FYI - http://socketo.me/
Yeah, I implemented a simple ircd once. Funny days... but I don't know of any library/framework that could help you with the websocket protocol level, and I'm too old for writing my own ;)