In today’s internet era, proxy servers play an increasingly important role. For mainland Chinese enterprises intending to expand their overseas business, using Hong Kong servers to set up proxy servers is a wise move. However, before deployment, we need to clarify a key question: what is a proxy server? This article will deeply analyze the types, working principles, and practical applications of proxy servers to help you fully understand this important concept.

Definition and Classification of Proxy Servers

A proxy server is an intermediate server located between the client and the target server, whose main function is to send requests and receive responses on behalf of the client to the target server. Based on the different working modes, proxy servers can be divided into two major categories: forward proxy and reverse proxy.

A forward proxy server is located on the client side, and the client needs to actively configure the IP and port of the proxy server. When the client initiates a request, the request is first sent to the proxy server and then forwarded by the proxy server to the target server. VPNs and scientific internet access tools are typical forward proxy applications.

A reverse proxy server, on the other hand, is located on the server side, and the client usually does not need any configuration to access it. When the client initiates a request, the request is directly sent to the reverse proxy server, which then distributes the request to the backend servers. Reverse proxies can hide the real server IP, enhancing security, and can also achieve load balancing, improving system availability.

Analysis of Proxy Server Working Principles

Regardless of whether it is a forward proxy or a reverse proxy, the working principle can be summarized into two steps: “intercept-forward.” Here is a simplified HTTP forward proxy processing flow:

  1. The client initiates an HTTP request and sends the request to the pre-configured proxy server;
  2. After receiving the request, the proxy server initiates a new request to the target server based on the request content;
  3. The target server processes the request and returns the response to the proxy server;
  4. The proxy server receives the response and forwards it to the client.

In this process, the target server can only see the IP of the proxy server and cannot obtain information about the real client. Here is a simple Nginx forward proxy configuration example:

server {
    listen 8080;
    location / {
        proxy_pass http://target_server;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
    }
}

Load Balancing Function of Reverse Proxy

Compared to forward proxies, a major advantage of reverse proxies is the ability to achieve load balancing. When there are multiple backend servers, the reverse proxy can distribute requests to different servers based on pre-set rules (such as round-robin, weighted round-robin, IP hash, etc.), thereby achieving the purpose of load balancing.

The following is an Nginx reverse proxy configuration that implements weighted round-robin load balancing:

upstream backend {
    server 192.168.1.101 weight=2;
    server 192.168.1.102 weight=1;
}

server {
    listen 80;
    location / {
        proxy_pass http://backend;
    }
}

In addition to load balancing, reverse proxies can also implement caching, compression, SSL termination, and other functions, greatly improving system performance and security. For cross-border access, proxy servers are even more indispensable tools.

In summary, proxy servers are an important component of modern network architecture. A deep understanding of what a proxy server is and how its work is crucial for optimizing network topology and improving system performance. When planning Hong Kong server deployment, consider introducing proxy servers to escort your overseas business.