Just wondering if anyone knows of any good on-line documentation on TCP/UDP Ports. Basically i want to know how to check if they are in use, learn how to close them, etc...
Thanks...
Try this link (Rutgers University) and do a search for lsof (either on your system or on Goggle ) - lsof is a program that lists open files (a port is a file in UNIX)
try this link for tcp/ip
information
http://www.cisco.com/univercd/cc/td/doc/product/iaabu/centri4/user/scf4ap1.htm
Quickest way to see if a port is in use is to simply use the 'netstat' command and grep for the port you are interested in. Also note that port alias names can be configured in '/etc/services' thus if a port does not appear to be in use check if an alias exists and grep accordingly.
Many implimentations of netstat have the -n flag that causes netstat to not look up a common name in /etc/services.