In today’s internet-driven world, where data constantly travels between millions of devices, it’s often not enough to establish a direct connection — you may need a “middleman.” That’s where a proxy server comes in. It acts as a bridge between you (the client) and the destination resource (server), handling network requests on your behalf. Understanding how proxies work is critical for network security, optimization, and access management.

What is a Proxy Server?

A proxy server (from the English proxy — representative, intermediary) is a server in a computer network that acts as an intermediary between a user (client) and other internet servers. All client requests go through the proxy first, which then forwards them to the destination server. Responses from the destination server also return to the proxy first before being sent back to the client.

Why Do We Need Proxy Servers? Key Functions:

Proxy servers serve many purposes, making them indispensable in modern network infrastructure:

1. Security and Access Control:
   • Filtering: A proxy can block access to unwanted websites (e.g., for controlling employee productivity).
   • Firewall: Protects the internal network by hiding its real structure and IP addresses.
   • Authentication: Requires username and password input for accessing the internet or specific resources.
2. Anonymity and Privacy:
   • The proxy hides the client’s real IP address from the destination server. The server only sees the proxy’s IP address.
   • This can be used to bypass regional restrictions or protect personal information.
3. Performance Optimization (Caching):
   • The proxy can store copies of frequently requested web pages or files in its cache. When a client requests a cached resource, the proxy delivers it directly, without contacting the origin server. This speeds up page loading and reduces network load.
4. Bypassing Blocks and Censorship:
   • If a resource is blocked in your region, you can connect through a proxy server in another region where access is allowed.
5. Logging and Monitoring:
   • A proxy can log all requests, allowing user activity tracking or traffic analysis.

Types of Proxy Servers: Forward and Reverse

Depending on their role and traffic direction, proxy servers are divided into two main types:

1. Forward Proxy ➡️🌐 (For clients accessing the internet)

A forward proxy server sits between the client (e.g., your office computer) and the internet. Clients configure their applications (browsers) to send all requests through this proxy. It acts on behalf of the client.

• Working with HTTP traffic:
  • Caching: A well-known example of a caching HTTP proxy is Squid.
  • Content Filtering: Blocks access to specific websites or categories of content.
  • Access Control: Determines who can access what online.
• Working with TCP traffic (SOCKS proxies):
  • SOCKS (Socket Secure) proxies are low-level proxies capable of forwarding any TCP traffic (and UDP in SOCKS5), not just HTTP.
  • They don’t inspect the content of the traffic at the application level — they just tunnel it. This makes them suitable for various apps like online games, messengers, FTP clients.
  • Examples: Dante, 3proxy can function as SOCKS proxies.

2. Reverse Proxy ⬅️🌐 (For servers receiving internet requests)

A reverse proxy server sits in front of one or more web servers (or other backend applications). When a user requests your website or service, the request first goes to the reverse proxy. It then forwards the request to the appropriate internal server.

• Working with HTTP traffic:
  • Load Balancing: Distributes incoming requests across multiple backend servers to balance the load, prevent overloads, and improve fault tolerance.
  • SSL Termination (SSL Offloading): The proxy handles all SSL/TLS encryption, reducing the computational load on backend servers. This simplifies SSL certificate management and improves web app performance.
  • Caching: Can also cache responses from your own servers to speed up delivery of frequently requested content.
  • Routing (URL Routing): Directs requests to different internal servers based on the URL, headers, or other request parameters.
  • Protection: Hides real backend server IP addresses from the outside world, and provides basic protection against DDoS attacks and other threats.
  • Examples: Nginx, HAProxy — powerful reverse proxies for HTTP traffic.
• Working with TCP traffic:
  • TCP Load Balancing: Distributes any TCP connections (e.g., databases, mail servers, game servers) across multiple backend servers.
  • SSL Passthrough: In this mode, the proxy doesn’t decrypt the traffic but passes the encrypted TCP connection through to the backend server, which performs the decryption itself.
  • Example: HAProxy is also well-suited for TCP traffic load balancing.

Conclusion

Proxy servers are powerful and flexible tools that can be used for a wide variety of tasks — from enhancing privacy and security for everyday users to optimizing complex corporate web services and protecting internal infrastructure. Understanding the differences between forward and reverse proxies, as well as their core functions, is key to effectively using network technologies. In upcoming articles, we’ll explore specific software solutions like Nginx, HAProxy, Dante, 3proxy, and Squid, and how they are applied in real-world scenarios.