Understanding SOCKS4 Protocol

SOCKS4 is a protocol that facilitates the routing of network packets between client-server applications via a proxy server. It's an earlier version of the SOCKS protocol, preceding SOCKS5.

What is SOCKS4?

SOCKS4 is a simple protocol for TCP proxy across network firewalls. It allows a client behind a firewall to gain full access to the Internet without requiring direct IP-reachability.

SOCKS4 protocol diagram
Key Features of SOCKS4
  • TCP Support: SOCKS4 is designed to proxy TCP connections.
  • Simple Authentication: Uses a simple authentication method based on IP address or username.
  • Firewall Traversal: Allows clients behind firewalls to access the internet.
  • No Encryption: SOCKS4 does not provide encryption or strong authentication.
  • IPv4 Only: SOCKS4 only supports IPv4 addresses.
How SOCKS4 Works
  1. Connection Request: The client sends a connection request to the SOCKS4 server.
  2. Request Details: The request includes the destination IP, port, and user ID (if authentication is used).
  3. Server Processing: The SOCKS4 server processes the request and attempts to establish a connection to the destination.
  4. Response: The server sends a response back to the client indicating success or failure.
  5. Data Transfer: If successful, data can now flow between the client and the destination server via the SOCKS4 proxy.
SOCKS4 and the OSI Model

SOCKS4 primarily operates at the Session Layer (Layer 5) of the OSI model, but it also interacts with other layers:

  • Session Layer (Layer 5): SOCKS4 establishes and manages the connection between the client and the proxy server.
  • Transport Layer (Layer 4): SOCKS4 works with TCP at this layer.
  • Network Layer (Layer 3): SOCKS4 handles IPv4 addresses at this layer.

For more information on these layers, visit our Session Layer, Transport Layer, and Network Layer pages.

SOCKS4 vs SOCKS5

SOCKS4 is an older protocol compared to SOCKS5. Here are the key differences:

  • Authentication: SOCKS5 supports multiple authentication methods, while SOCKS4 has limited authentication capabilities.
  • UDP Support: SOCKS5 can proxy UDP traffic, but SOCKS4 only supports TCP.
  • IPv6: SOCKS5 supports IPv6, while SOCKS4 only works with IPv4.
  • Flexibility: SOCKS5 is more flexible and can handle various types of network traffic more efficiently.

For more information on SOCKS5, visit our SOCKS5 page.

Use Cases for SOCKS4
  • Legacy System Support: Some older systems or applications may only support SOCKS4.
  • Simple Proxying Needs: When basic TCP proxying is required without the need for UDP or advanced authentication.
  • Firewall Bypassing: SOCKS4 can be used to bypass simple firewalls in some scenarios.
  • Lightweight Proxying: In situations where the additional features of SOCKS5 are not needed, SOCKS4 can be a lighter alternative.
Security Considerations

While SOCKS4 can be useful in certain scenarios, it has several security limitations:

  • Limited Authentication: SOCKS4 has very basic authentication, making it vulnerable to unauthorized access.
  • No Encryption: SOCKS4 does not provide any encryption, potentially exposing data to eavesdropping.
  • IPv4 Only: The lack of IPv6 support can be a security concern in modern networks.
  • No UDP Support: This limitation can impact the functionality of certain applications and protocols.
  • Outdated: Being an older protocol, SOCKS4 may not be maintained or updated to address new security threats.

Due to these limitations, it's generally recommended to use SOCKS5 or other more secure proxying methods when possible.