Hey guys, I got some info. about the Instant Messaging. The messages don’t hop between MSN or Yahoo servers. The servers are just intermediary. When a person logs into his/her account from MSN or Yahoo messengers, the contact list of that person is downloaded to the messenger and the server checks to see if the people in his/her contact list are online or not and this info. too is sent to the messenger.

So when a person starts a conversation with someone, that person’s messenger (and the respective server) knows the IP address of the other person and a peer-to-peer connection is established between the two parties. [Note: The IP is already known! So how can we find this out?]

So if we know the IP address of the person we want to talk to then we can have a conversation without a messenger. We need some sort of a messaging service because we cannot find out whether the person we want to chat to is online or not and also because the IP address of most of the people change each time they log in. One advantage of an instant messaging service is that a person can find out who is online at any moment.