From SHELL FU: http://www.shellfu.org

The command below will monitor open TCP connections:

watch -n 1 "netstat -tpanl | grep ESTABLISHED"

This shows connections by processes for your user, or if done as root (“sudo netstat”) all processes.

Another option to perform the same task is:

sudo lsof -i -T -n

Again, ‘watch’ could be used with this, or adding -r as an option will make lsof refresh the output.