node.js express socket.io port 3000 in use

Question

I\'ve been following this(http://socket.io/get-started/chat/) tutorial on how to make a simple chat application using socket.io.

I tried to however use Express to create

Answer 1

I had (forgotten that I had) previously installed ntop, which by default also uses port 3000, and was therefore getting the same error as described here.

As others have mentioned, use netstat or lsof to find the offending service (and prefix the command with sudo, to get the correct process name):

sudo lsof -P | grep ':3000'

- or -

sudo netstat -anp tcp | grep 3000

On Ubuntu, the service is disabled with (simply):

service ntop stop