Can nginx be used as a reverse proxy for a backend websocket server?

You can't use nginx for this currently^{[it's not true anymore]}, but I would suggest looking at HAProxy. I have used it for exactly this purpose.

The trick is to set long timeouts so that the socket connections are not closed. Something like:

timeout client  86400000 # In the frontendtimeout server  86400000 # In the backend

If you want to serve say a rails and cramp application on the same port you can use ACL rules to detect a websocket connection and use a different backend. So your haproxy frontend config would look something like

frontend all 0.0.0.0:80  timeout client    86400000  default_backend   rails_backend  acl websocket hdr(Upgrade)    -i WebSocket  use_backend   cramp_backend   if websocket

For completeness the backend would look like

backend cramp_backend  timeout server  86400000  server cramp1 localhost:8090 maxconn 200 check

How about use my nginx_tcp_proxy_module module?

This module is designed for general TCP proxy with Nginx. I think it's also suitable for websocket. And I just add tcp_ssl_module in the development branch.

nginx (>= 1.3.13) now supports reverse proxying websockets.

# the upstream server doesn't need a prefix! # no need for wss:// or http:// because nginx will upgrade to http1.1 in the config belowupstream app_server {    server localhost:3000;}server {    # ...    location / {        proxy_pass http://app_server;        proxy_http_version 1.1;        proxy_set_header Upgrade $http_upgrade;        proxy_set_header Connection "upgrade";        proxy_set_header Host $host;        proxy_set_header X-Real-IP $remote_addr;        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;        proxy_redirect off;    }}