We all know netstat which can show you all the important network connections - if you remember how to use it. I always forget and it's hard to find it again. So I'll post the commands I found most useful in here.
This command displays all active TCP connections:netstat --tcp --programs --numeric-ports netstat -tp --numeric-ports (shorter)
Aktive Internetverbindungen (ohne Server) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 localhost:3306 localhost:38525 VERBUNDEN 3024/mysqld tcp 0 0 localhost:3306 localhost:38527 VERBUNDEN 3024/mysqld tcp 38 0 picard:36800 ldap.**** CLOSE_WAIT 1146/dbus-daemon
Parameter --programs adds the program name info, --numeric-ports prevents netstat of hiding the port numbers. To display UDP connections use --udp.
netstat --tcp --listening --programs --numeric-ports netstat -tlp --numeric-ports (shorter)
Aktive Internetverbindungen (Nur Server) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 *:3306 *:* LISTEN 3024/mysqld tcp 0 0 *:22 *:* LISTEN 2630/sshd tcp 0 0 *:8080 *:* LISTEN 12439/java
If you want to have the output continuously refreshed use "watch -n1". And if you've got a netstat that displays the information partially in another language (german in my case) you can set the locale to have it all in english. That will make using grep so much easier...
LANG=en watch -n1 netstat -tlp --numeric-ports
Some of the examples in here were copied from http://www.linuxhowtos.org/Network/netstat.htm .
