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How Does Instant Messaging Work?

written by: •edited by: Michele McDonough•updated: 1/15/2011

If you've spent any amount of time online, chances are, you've used instant messaging as a means for communicating with others while online. How does instant messaging work? Learn about the ins and outs of what makes your message pop up on someone else's screen here.

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    The Instant Messaging Phenomenon

    How does instant messaging work? Instant messaging has been around for about 30 years, though it's only been in the form we use on a regular basis since the late 1990s. It is incredibly easy to talk with friends, family, clients, and strangers from anywhere in the world and get an instant response.

    If you're like many, until now, you probably have't given much thought to what it is that makes instant messaging work. In the early days of the computer and computer networks, instant messaging was a function of what was known as timesharing, a resource created through the development of CTSS in the 1960s to allow multi-tasking on computers.

    While the modern instant messaging program has come a long way from the CTSS .RECORD system that allowed users on the computer to leave messages for each other, instant message at its core is still mediated through a server and then the messages are distributed to the recipients. You may finally be wondering for the first time ever as you contemplate some of the things you've sent through the internet, how does instant messaging work?

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    1. User One Signs on the Computer

    The instant messaging process begins when the initiating user connects to the internet and opens his or her instant messaging software. A message is then typed into the user interface (the box that displays the conversation in the top half, and the message you are typing in the bottom portion.

    Another key feature of your instant messaging program is the contacts list. This list shows you who is online, who is idle, and who is offline. When you sign onto the server, a signal is transmitted through the Internet service provider to the provider's servers, and in turn, is signaled as being "online" to other messenger users.

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    2. User One Selects Another User and Sends a Message

    Once online, the initiating user will often click, or double click, on another user's screenname. This allows the user to now type into the user interface the message he or she would like to send. Once the message is typed, then the user either uses the mouse to click on the "send" button or simply hits "enter" to send the message.

    The message then is coded into computer language and it travels through the ISP and the ISP's server to the other server, and appears on the second user's screen once the computer decodes it. While this seems instantaneous, the process actually takes a second or two to deliver the message to you in tact. When the ISP's server is overloaded, then instant messages can be slowed down in their transmission process.

    Vocal usage of instant messaging also tends to be slower, or jumpy - this is because there is a lot of rich information being translated into and out of code between two computers. This can give the jumpy effect that you get sometimes when chatting using a webcam.

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    3. How Does the Message "Know" Where to Go?

    ICQ, the original instant messaging program that preceded AOL's modern messaging interface was known for using numbers instead of using name. The way messages are transmitted is not that different from this. Every computer has a unique number, called an IP address, that tells other computers where to route the information being transmitted to and from the computer. When you use an instant messaging client, the client has the other user's IP address and port number stored in its databases. When you click "send," the message is sent to the other IP address and port, much in the way a letter is delivered through the mail using a street address, only with an instant messaging program, a lot of information can be transmitted very quickly.

    Because information is sent directly to and from your computer's IP address, be especially vigilant in preventing instant messaging threats to your computer. Be sure that you do not click on unexpected links or download unexpected files sent to you in instant messages, they could be virus, spyware, or other malware programs that could cause problems for you.

    Finally, when your computer is having a hard time instant messaging with others, try to remember that you might be using the client during a period of high traffic. When this happens, sometimes the servers are overloaded and it slows down the instant messaging process.