How to get active connections in Unix

Hi All,
I have to find out how many active connections with other machines are there,then list the remote machine IP address and type of connection.
When u say type of connection what does it means TCP,UDP ram. then what is UNIX active connection
Please let me know as soon as possible.

Thanks in advance.
Jatin

man netstat.

netstat <options> | grep -i established

netstat -an | grep ESTABLISHED

my bad, yes it should be "established". misinterpretation. thanks for correction.