How can I check connections with my linux server?

Netstat is a very usefull command to verify if you’re connecting with other servers, and if other machines are connection with you.But also extra options, like routing, traffic can be seen with netstat.

Check all ports, ports that are listening and ports that are connected:

netstat -an
netstat -an | grep LIST
netstat -an | grep ESTA

Show which process is using with port

netstat -tulpn

Show statistics by protocol

netstat -s

Show routing for your server

netstat -rn

Show statistics for your interfaces

netstat -i