What port do instant messenger program such as AIM or MSN use?

They do not all use the same port. I cannot test this because I don't use AIM or MSN messenger and don't want to download either but...Try doing a netstat -a on your dos prompt (command.com or cmd.exe) when you have the program running.

For msn we figured that out last week sometime here:
http://www.undergroundnews.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=3;t=000272

As for aim, I don't have the slightest clue.

Infinite

dashocker,

The netstat idea is good, now I just need a willing volunteer with AIM. I refuse to put that on my machine! Does anyone have AIM and would be willing to try that test?

Infinite,

Thanks for the help. Those sites were exactly what I wanted.

"I refuse to put that on my machine!"

Use trillian.

nomel,

What is trillian?

It's a chat client that supports a number of protocols. AIM, MSN, Yahoo, IRC, and Jabber. http://www.trillian.cc

Protocol | TCP | UDP
MSN Messenger | 1863
Mirabilis ICQ | dyn >=1024 | 4000
Yahoo [Voice] | 5000-5001 | 5000-5010
Yahoo [Text] | 5050
Yahoo [Cams] | 5100
AIM | 5190 | 5190
AOL ICQ | 5190, dyn >=1024 |

Aim's Image DCC is port 4443..