IP Port Numbers


Every once in a while, I check my system log to see which packets are bouncing off my firewall. I usually see half a dozen a day, usually directed at ports I'm not familiar with.

Does anyone know of a good, more-or-less comprehensive list of IP port numbers? I mean, port 80 is http, I think 110 is smtp, 22 is I think ssh, etc. But what, for example, is port 53, or 111, or 515? There must be a list of them out there somewhere...
The standard port assignments can be found in RFC 1700 which should answer the ones you mentioned. Ports used by specific applications only most likely won't show up there. There's also a file which comes with nmap (called nmap-services) which lists many of these application-specific uses.
try this on almost any unix-like computer:

cat /etc/services | grep 111

you'll see something like:
sunrpc 111/tcp portmapper # RPC 4.0 portmapper TCP
sunrpc 111/udp portmapper # RPC 4.0 portmapper UDP

basicaly, every unix-like OS has a file in /etc, called services, and lots of services look there to decide what port to run on.