How to identify app on port number

[codnaway]

Just started playing with a port scanner and found some interesting results. The scanner reported some open ports that are usually reserved for standard apps (like tcp 21) and some high number ports and suggests I investigate further.

How do I determine what is running on a given port?

[dmorison]

Doing a Google Groups search for "Port X" is pretty good at identifying services as many people have posted Usenet questions along the lines of "What is running on Port X" over the years.

There's also the official list at IANA:

[iana.org...]

[Xoc]

You can find information about what is running by executing

netstat -a -b

from a command shell. Netstat -a, by itself also gives useful information.