Hi, I'm using:
and i have a comunication problem with Opera when socket.io and webserver are located on different port / host.
I have created a simple example (based on your chat example) to reproduce an error: kitek/socket.io@9b7d548
I think Opera can't establish connection to socket.io and it is associated with support for Cross-Origin Resource Sharing.
I use Opera as well and it works for cross-domain via jsonp. You are using quite non-production scheme.
My working environment is site.local, comet.site.local(instead of localhost:300x). All proxied through HaProxy. It emulates live environment on production.
Opera can have issue especially with localhost. You can try to put it in your etc/hosts alias to 'yoursite.local' and use it instead of localhost.