Hosting a Web Server

Every time you open your browser to check a news article or read documentation, you use the Hypertext Transfer Protocol (HTTP). Developed in 1989, HTTP was built to let people share documents between computers over simple network links.

Today, almost every business runs a private Internal Web Server. Companies use these internal sites for staff directories, helpdesk tickets, and office announcements. Because the server stays inside the building, the website is fast and protected from the outside internet.

How Web Browsers Request Web Pages

HTTP works using a simple request and reply conversation. Your browser asks for a file, and the web server sends that file back:

1. Opening the Door (TCP Handshake): Before exchanging any text, your computer and the server shake hands over the network to establish a reliable connection targeting Port 80.
2. Sending the Request: Your browser sends a short text message asking for the home page:

   GET /index.html HTTP/1.1
   Host: 192.168.1.100
   Accept: text/html

3. Server Sends the Reply: The web server looks up index.html on its drive and sends it back with a status code:

   HTTP/1.1 200 OK
   Content-Type: text/html
   
   <html><body><h1>Welcome to the Office Intranet</h1></body></html>

4. Browser Shows the Page: The browser reads the HTML code, sets up colors and fonts, and displays the final visual page on your screen.

Notice that modern webpages rarely contain only text. When your browser downloads the initial HTML file, it scans the document for references to company logos, style sheets, and scripts. For each referenced resource, the browser opens another request to Port 80 until every image and asset appears on your screen.

Status Code	Status Name	What It Means in Practice
200 OK	Success	The server found the file and sent it back without problems.
301 Moved	Redirect	The page moved to a new address; your browser goes to the new link automatically.
403 Forbidden	Access Denied	The file exists, but your user account does not have permission to view it.
404 Not Found	Missing File	You typed a link or file name that does not exist on the server.
500 Error	Server Trouble	The server software had an internal error while trying to build the page.

Why HTTP Uses Port 80

When you type http://192.168.1.100 into your browser address bar, you do not need to write :80 at the end. Web browsers automatically assume Port 80 whenever you type http://. If you configure a web server on a non-standard port like 8080, users must type http://192.168.1.100:8080 to reach it.

Internet standards bodies reserved ports below 1024 as well-known ports so that clients do not have to guess where a service lives. On Unix-like operating systems, binding to Port 80 requires administrator privileges, which provides an extra layer of security so normal user programs cannot hijack official company websites.

Field Incident: The Accidental Port Conflict

In real office deployments, a common issue occurs when someone installs two programs on the same server that both want Port 80. For example, if a developer installs a local testing server while an existing company intranet is already running, the second software will fail to start. It displays a message saying "Address already in use".

Only one program can listen to a single port on a single IP address at the same time. Learning how Port 80 works allows network engineers to verify that the web service is bound to the right port and running properly.

The Bridge to Name Lookups

Now our office server reliably hosts the company intranet on Port 80, and any workstation can open it by typing http://192.168.1.100. But how many of your co-workers will remember that IP address next week? What if that server hardware needs to be upgraded and its IP changes? In our next chapter, we will see how a DNS Server gives that numeric address a friendly name that everyone can remember.

In your hands-on lab on the right, you will connect to the web server by entering its numeric IP address directly. As you do, notice how simple the HTTP transaction is, and why adding a name service will be the logical next step for corporate usability.