Proxy Server is an intermediate server located between the client and the target server. It can send requests to the target server on behalf of the client, receive and forward responses from the target server. The proxy server can provide some special functions, such as caching, filtering, security control, etc., thereby improving the efficiency and security of network access. Socks proxy (Socket Secure) is a common proxy server protocol, mainly divided into two types: Socks4 and Socks5. This article will compare the differences between Socks4 proxy and Socks5 proxy in terms of protocol structure, functional characteristics, security, etc.

1. Agreement structure

1. Socks4 proxy

The Socks4 proxy is the earliest version. It was designed by David Koblas in 1993 and is the earliest widely used proxy protocol. The Socks4 proxy protocol is based on the SOCKSv3 protocol and uses TCP connections for communication.

2. Socks5 proxy

The Socks5 proxy protocol was improved on the basis of Socks4. Because its designer believed that the Socks4 protocol had some security issues, the Socks5 protocol was launched in 1996. Compared with Socks4, the Socks5 proxy protocol has undergone major changes in the protocol structure.

2. Functional features

a. Socks4 proxy

(1) Only supports TCP connection

The Socks4 proxy protocol only supports TCP connections and therefore cannot handle UDP packets. This is also one of the main reasons why the Socks4 protocol was replaced by the Socks5 protocol.

(2) Does not support authentication

The Socks4 proxy protocol does not support authentication, that is, the client does not need to provide a username and password to establish a connection. This reduces security to some extent.

(3) Only IPv4 addresses can be proxied

The Socks4 proxy protocol can only handle IPv4 addresses, not IPv6 addresses. With the popularity of IPv6, this has also become a limitation of the Socks4 protocol.

b. Socks5 proxy

(1) Support TCP and UDP connections

The Socks5 proxy protocol not only supports TCP connections, but also supports UDP connections, which can implement more functions, such as FTP file transfer, Internet voice, video, etc.

(2) Support identity verification

The Socks5 proxy protocol supports multiple authentication methods, such as username/password authentication, GSS-API authentication, etc., which improves security.

(3) Support IPv6 address

The Socks5 proxy protocol can handle IPv6 addresses, overcoming the limitations of the Socks4 protocol.

(4) Support agent chain

The Socks5 proxy protocol supports proxy chaining, that is, the client can achieve network connections through multiple proxy servers, improving flexibility.

3. Security

a. Socks4 proxy

Since the Socks4 proxy protocol does not support authentication, it is less secure. Attackers can use this to disguise their identity and access restricted resources, thereby posing a security threat.

b. Socks5 proxy

The Socks5 proxy protocol supports multiple authentication methods, improving security. At the same time, the Socks5 protocol also adds a "Request Type" field, which allows more detailed control of the connection, such as restricting access to specific IP addresses, restricting access to specific ports, etc., thus improving security.

4. Summary

To sum up, there are obvious differences between Socks4 proxy and Socks5 proxy in terms of protocol structure, functional features, and security. The Socks4 proxy protocol has simple functions and low security, and has been gradually replaced by the Socks5 proxy protocol. The Socks5 proxy protocol is more powerful and secure, and can meet more network needs. Therefore, when choosing a proxy server, you need to choose a suitable protocol type based on the actual situation.