What's This 'Internet' I Keep Hearing About? - Part Eight - Meaningful Dialog

I've fully covered the essence of how messages are delivered over the Internet, but so far these messages are completely raw and meaningless. Before meaningful communication can occur we need to layer on yet another protocol (recall IP and TCP protocols are already layered over our physical network).

There are many protocols that work on the communications already established, including:

• HTTP - for web pages, typically read in web browser software
• POP3 - for reading e-mail
• SMTP - for sending e-mail

I'm not going to go into the details of any of these protocols because it's not really relevant unless you actually need to know it.

The information transferred via a protocol is usually a request for something, or a response for something requested. For example, with HTTP, a client computer requests a certain web page from a server via HTTP and then the web server, basically, responds with the file embedded within HTTP.

Each of these protocols operates on more or more so-called 'ports', and it is these 'ports' that allow the computers to know which protocol to use. For example, a web server (special computer software running on a server computer that serves out web pages) uses a port of number '80', and hence when the server receives messages on that port it passes them to the web server software which naturally knows that they'll be written in HTTP.