Web Hosting Technology Overview - Servers

When a server receives a request from a user to display a web page, there are several things that it has to take into account. First, it has to determine what the request means. Servers can serve many different purposes, and may send out information other than just web pages. It can tell what request is for which material based on what port the request is being sent over. Requests for web pages are sent over port 80.
On web servers, all requests over port 80 have to be handled by some kind of program. The most common programs are Microsoft’s IIS and Apache. The function of these programs is to interpret requests sent over port 80 as well as keep track of all of the files that are going into websites. They are basically the part of the computer that handles the request for a web page to be sent to a user.
Once the server has determined that it is being asked for a web page, it has to figure out which one the user is requesting. Servers often host more than just one website. It refers back to the domain name that the user originally requested. It then begins looking for the specified web page within the directory of files that belongs to that domain name.
Once it has found the specific file that is being requested, the server has to figure out what to do with that file. The server cannot simply send the file back to the requester; many files contain sensitive data that webmasters do not want sent out to the general public. Other files are specifically intended to be interpreted by the server before it sends a response. The server is configured to treat different file types in different ways; there is a rule for each of them.
Once the server has determined what to do with the file, it will figure out what to send back to the user. This is the interpreted file. Sometimes this will just be the file itself. Other times it may not send back anything at all; it will just block the request. Depending on what the server decides to send back, the user’s computer will then interpret the response and display something for the end user. Now, the web page has finally been sent back to the user.