SOCKS

2026-06-15

A bit on the socks protocol, which is used for creating proxies.

SOCKS protocol

The protocol is used for forwarding internet traffic, particularly TCP/IP via a proxy server. Version 5 later added support for ipv6 and UDP that also allows dns lookups.

The handshake works as follows:

Client connects and sends a greeting, which includes a list of authentication methods.
Server chooses a method.
Client sends multiple messages now.
Finally the regular connection requests occur:
- One packet from client to server with the version, command code, destination port, destination IP, and the user ID string.
- Server responds with version, reply code, destination port and IP, which the client should bind to if the command code was BIND.

SOCKS protocol

The protocol is used for forwarding internet traffic, particularly TCP/IP via a proxy server. Version 5 later added support for ipv6 and UDP that also allows dns lookups.

The handshake works as follows:

Client connects and sends a greeting, which includes a list of authentication methods.

Server chooses a method.

Client sends multiple messages now.

Finally the regular connection requests occur:

One packet from client to server with the version, command code, destination port, destination IP, and the user ID string.
Server responds with version, reply code, destination port and IP, which the client should bind to if the command code was BIND.