I am interested in creating an instant messenging program just to get experience and have more projects to show potential employers. But I have a few questions. How do AOL, ICQ, MSN, etc, work in a general sense? I mean, I realize you have to sign up for their service, but once you log on, are you connecting to AOL''s servers or what? If I wanted to create my own instant messenging system, would I have to host the conversations or how would two people with my program communicate? I appreciate any and all comments/suggestions. Thanks a million.

This site has some information on the protocol that AIM, ICQ, and other IMs use.. Should give you some idea of how they work

Hope that helps..
Lord Hen

"I am free of all prejudices. I hate everyone equally." - W. C. Fields

[edited by - Lord Hen on December 2, 2008 2:32:49 AM]

They connect to a central server, and log in using a username and password. Some systems download a buddy list from that server. Then a connection with that server is maintained so that changes in buddy status are sent to you as appropriate. When you initiate a conversation, it''ll send a message to the central server and either decide to pass on data via the server, or return the other person''s IP address and listening port info (for example) so that you can establish a direct connection. The central server waits for you to either signal that you''re going offline, or to disconnect, so that it can then inform all your buddies that you''re gone. Rinse and repeat.

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quote:Original post by voigtkampf
I am interested in creating an instant messenging program just to get experience and have more projects to show potential employers.

Funny you should mention this, it happens to be one of my favorite question to ask on an interview. I ask the candidate how she/he would design an IM system similar to MSN/ICQ, and we discuss around that for about an hour. The important thing is of course not to know all about instant messaging, but more to see how the candidate approaches the problem.