The following command is useful to watch what connections from the Internet are being made on your Linux system:
watch -d -n1 lsof -i
This will run the command lsof ( with the list interface option ) ever second and highlight differences
You can use the watch command with netstat as well to see connections:
watch -d -n1 'netstat -anp | grep -i stream'
The following command will show socket connections and the process that is bound to a port: