I’m seeing the same issue. Any luck resolving it?
Make sure to install socket.io in the /var/lib/cloud9 directory. You can’t do this from cloud9 so you’ll need to use a shell (SSH) and enter this:
cd /var/lib/cloud9
npm install socket.io
For more details and an example on using socket.io, see https://github.com/lgxlogic/BoneScript-SocketIO
Hope this helps.
Roland Groeneveld
Logic Supply
www.logicsupply.com