The Internet is comprised of clients and servers. For example the web page you are reading right now is actually a computer file that is on the College of Engineering’s web server. The computer you are using to view this page is the client computer. The client and the server are connected by what is called the Hypertext Transfer Protocol, or HTTP for short.
Both computers must understand this protocol to communicate with each other. This is done by the programs that are used. On the client side it is your browser and on the server side it is one of many types of web server programs. We use the Apache web server, for example.
HTTP uses the Uniform Resource Locator, or URL, to communicate between the client and the server. This URL tells the server which web page it needs to send to the client. And so the URL is basically an address on the web. If you look at the top of your browser you will see that the URL for this web page is:
The address can be broken down like this:
This tells the server that the client is requesting a web page. The client can also request other things from the server (not discussed in this tutorial).
This is the host that the client computer wishes to connect to. It is basically the “name” of the computer that the web pages are stored in.
This is the path to the specific web page the client computer wants to see. It is basically a listing of the directories on the server computer where the file is stored. So this web page (webbasics.html) is in a directory called “web” that is within a directory called “how” that is in turn within a directory called “ens” that resides at the root of the web server.
Another important protocol that is used to communicate between clients and servers is Hypertext Markup Language, or HTML. This is the language that is used to actually create the web pages. It tells your browser how to display the content of the computer file on your browser window.
How the Web Works
- Your browser tells your computer to send out a request for a specific URL address.
- This request is sent to a number of other computers including domain name servers, firewalls, routers and gateways. Each one of these computers have a different task, but the bottom line is that they make sure that the request is sent to the correct server.
- The server computer accepts the request and the web server program determines exactly what is wanted.
- The server computer then sends out the web file that was requested.
- The web file is sent to the computers mentioned in step number 3. These are not necessarily the same physical computers as before, but the tasks that they perform will be the same.
- Your computer receives the web file the server sent.
- The browser parses the HTML contained in the web file and displays the contents in the browser’s window.
- You click a link on the page and it starts all over again with step number 2.