How Does Instant Messaging Work?

Holding a Conversation

Your instant messaging program beings the process of communicating with others by connecting you to a server used by everyone who uses the same program.

Once connected, your program sends your specific connection information, including your IP address and the port you are using, to the server. This is important information that is used in connecting with others.

Once you've selected someone to talk to (normally from a list of contacts you've maintained of friends or acquaintances who have given you their contact information), your instant messaging program sends any messages you choose directly to the IP address and port of the person in question. This is what enables conversations to happen in real-time, as you aren't sending a message to a server and back to another computer. Two computers are directly connected to each other at that point, and can send messages to each other as rapidly as they choose.