Web Servers: An Overview and Types

Many times we wonder how a web container/ web-server (e.g. Tomcat) works? How they handle the incoming HTTP requests coming from all over the world? What are the things which make it happen behind the scene?

In this article, we are going to read what web server is, how they work, and their type.

What is a WebServer?

A web server is a software and hardware that uses HTTP (Hypertext Transfer Protocol) and other protocols to respond to client requests made over the World Wide Web.

The main job of a web server is to display the content by storing, processing, and delivering webpages to users.        

Not only the HTTP protocol, but web servers also support SMTP (Simple Mail Transfer Protocol) and FTP (File Transfer Protocol), used for email, file transfer, and storage.

A web server is essentially the backbone of the internet. It’s never disconnected from the web and operates 24/7 to ensure uninterrupted service. Each web server has a unique identifier, an address composed of four numbers ranging between 0 and 255, separated by periods. For instance: 127.0.0.1.

This numerical address ensures that every server can be located accurately in the vast digital space.

The process is an example of the client/server model. All computers that host Web sites must have Web server programs.

How Does a Web Server Process Your Request?

When you search for something online, here’s what happens:

• Browser Translates the URL

Your browser converts the URL (like www.example.com) into a machine-readable format using the Domain Name System (DNS). DNS acts like a phonebook, translating human-readable domain names into the numerical IP addresses of web servers.

• Making a Request

Once the translation is complete, the browser sends a request to the web server. This is typically done via the HTTP (HyperText Transfer Protocol) or another similar protocol.

• Checking the Cache

Sometimes, the requested data might already exist in the browser's cache memory. If available, the content loads instantly without needing to communicate with the server.

• Server Responds

If the content isn't in the cache, the web server processes the request, retrieves the required data (like a web page, video, or image), and sends it back to the browser through the same protocol.

What is HTTP?

Hypertext Transfer Protocol, commonly known as HTTP, is the foundation of communication between various computing systems. It facilitates the seamless exchange of information and data across networks, ensuring the efficient transmission of data packets.

HTTP requests are transmitted unencrypted, meaning they are exposed and vulnerable to those with advanced technical expertise. Using basic tools can allow individuals to intercept and interpret the data being exchanged in these requests, which is where HTTPS comes into the picture.

What is HTTPS?

Hypertext Transfer Protocol Secure, or HTTPS, safeguards data transfer between web servers and browsers. HTTPS secures data transmission with a digital security protocol that utilizes cryptographic keys for encryption and data validation. This is commonly done by obtaining a Transport Layer Security (TLS) or Secure Sockets Layer (SSL) certificate.

By doing so, they ensure that all communication and data exchange between the users and the server is encrypted and protected from any potential malicious activity.

HTTP v/s HTTPS: Which is better?

Types of Web Servers:

1. Apache HTTP Server

• Developer: Apache Software Foundation
• Key Features: Free and open-source
• Compatible with multiple operating systems, including Windows, macOS, Unix, Linux, and Solaris
• Powers approximately 60% of the world's web machines
• License: Requires the Apache License

2. Microsoft Internet Information Services (IIS)

• Developer: Microsoft
• Key Features: Designed exclusively for Microsoft platforms
• Not open-source
• Widely used for hosting websites and applications on Windows servers

3. Nginx

• Key Features: Open-source and highly popular among system administrators
• Known for lightweight resource utilization and scalability
• Functions as a proxy server and load balancer in addition to being a web server

4. Lighttpd

• Key Features: A free web server included with the FreeBSD operating system
• Renowned for its speed and security
• Consumes minimal CPU resources, making it an efficient choice for smaller setups

5. Sun Java System Web Server

• Developer: Sun Microsystems
• Key Features:Free to use
• Compatible with Windows, Linux, and UnixSuitable for medium to large-sized websites due to its robust capabilities

The Dynamic Duo: Web Servers and Application Servers

In the world of web-based applications, two critical components ensure the seamless delivery of content and functionality to users: the Web Server and the Application Server. Understanding their roles, interactions, and importance is essential for developers, architects, and tech enthusiasts alike.

The Role of the Web Server

A web server is the first point of contact for a client’s request. Before reaching the application server, all requests are handled by the web server, which excels at serving static content such as:

• HTML files
• Images
• PDFs or ZIP files

The web server retrieves files from the server’s storage, formats them for web browsers, and transmits them over the network. Its design focuses on efficiently delivering static content to a large audience. However, web servers have limitations—they cannot execute logic or generate dynamic content.

Why Do We Need an Application Server?

Static files are not enough when your application demands interactivity, logic, or data retrieval. Enter the Application Server, which extends the capabilities of the web server by:

• Processing dynamic requests
• Generating HTML on the fly
• Accessing databases for content

Dynamic content such as real-time stock prices, personalized dashboards, or transaction histories requires the intelligence that only an application server can provide.

Bridging the Gap: The Application Server Plug-In

To ensure a harmonious relationship between the web server and the application server, an application server plug-in is installed on the web server. This plug-in:

• Identifies requests for dynamic content (e.g., JSPs or Servlets).
• Forward these requests to the application server for processing.
• Receives the generated HTML and returns it to the client as if the web server handled it.

The plug-in operates based on an XML configuration file that maps specific requests to the application server’s IP address and port.

How the Relationship Works: A Conversation

Imagine a dialogue between a web server and an application server:

Application Server: Hey Web Server, I hear you’re great at serving static files. But when it comes to dynamic requests, you might struggle.

Web Server: Absolutely! I can’t handle those JSPs and Servlets. What should I do?

Application Server: No worries. Just pass those requests to me. I’ll handle the heavy lifting and give you the HTML to send back to the client.

Web Server: Sounds good! How will I know which requests to send to you?

Application Server: Check the XML file I provide—it lists all dynamic content.

From Request to Response: The Workflow

1. Client Request: The user sends a request for a JSP or Servlet.
2. Web Server Processing: The web server identifies the request type using the XML configuration file.
3. Forwarding: The web server forwards the request to the application server based on the provided IP and port.
4. Application Server Handling: The application server invokes the relevant Servlet or JSP, processes the logic, and generates a response.
5. Response Delivery: The application server sends the processed HTML back to the web server, which then delivers it to the client.

Inside the Web Container

When the application server receives a dynamic request:

• It loads the corresponding Servlet or JSP (if not already loaded).
• Creates a thread to process the request.
• Maintains the Servlet in memory for future requests until the server shuts down.

What is a Servlet and What Does It Do?

A Servlet is a Java class used to extend the capabilities of servers that host applications accessed via a request-response programming model. In simpler terms, it is a server-side component that processes incoming requests from clients and generates responses, typically over HTTP.

How Does a Servlet Work?

At its core, a Servlet is a Java class that can handle HTTP requests and generate HTTP responses. When a client (like a web browser) makes a request, the Servlet processes that request and sends a response. Here's how the process works:

1. Request Handling: The Servlet container (like Tomcat) manages the HTTP request. It abstracts the details of networking, allowing developers to focus on business logic.
2. Response Handling: Once the Servlet processes the request, the container wraps the response in an HTTP response object and sends it back to the client.

Example: If a user fills out a form on a website, a Servlet can capture the form data, process it, and save it to a database. The Servlet acts as the controller in the Model-View-Controller (MVC) design pattern, and it often delegates tasks like database operations to other components such as JavaBeans or EJBs (Enterprise JavaBeans).

What Does a Servlet Do?

A Servlet can perform any task the developer wants, but it is typically used to implement control logic in web applications. Some common tasks include:

• Processing user input: A Servlet can capture form data submitted by a user on a website.
• Interacting with databases: Though Servlets can interact with databases, it's generally better to delegate database operations to other components like JavaBeans or EJBs.
• Generating dynamic content: Based on the request, a Servlet can generate dynamic HTML or other content and send it back to the client.

Servlet Containers: Tomcat Example

Servlets are hosted and executed within a Servlet container. These containers, like Apache Tomcat, handle network communication, request parsing, and response handling. The container ensures that developers don’t need to worry about low-level details such as network connections.

What is a JSP (JavaServer Pages)?

A JavaServer Page (JSP) is a technology used to create dynamic, server-side web pages in Java. It is similar to Servlets but focuses more on the presentation layer rather than the control layer.

How Does a JSP Work?

A @JSP is essentially an HTML page with embedded Java code. When a client requests a JSP page, the server compiles it into a Servlet. The logic in the JSP is executed, and the resulting content (usually HTML) is sent back to the client.

1. JSP and Servlets Together: While a Servlet handles the application logic, a JSP is typically used to display the results. The Servlet processes the data (such as retrieving records from a database), and the JSP is responsible for formatting and displaying that data.
2. Embedded Java in HTML: In a JSP, you can write Java code directly within the HTML using special tags, like <% %> to execute Java code, <%= %> to output expressions, or <%@ %> for directives like imports.

Servlets vs JSP

Why Does This Matter?

Understanding how web servers operate not only helps tech enthusiasts but also empowers businesses to optimize their online presence. Efficient servers and well-designed caching mechanisms can significantly improve user experience and website performance.

Next time you type a URL into your browser, remember the intricate journey your request takes. The seamless experience you enjoy is powered by the complex but fascinating process of web servers working tirelessly in the background.

Stay tuned for more tech insights!

References

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