SOCKS is a general-purpose proxy protocol for relaying messages between application client and application server via SOCKS proxy server. The SOCKS protocol is used between SOCKS client and SOCKS proxy server. SOCKS V4 supports only TCP CONNECT and TCP BIND commands, while in SOCKS V5 also UDP relaying is supported. Additionally, SOCKS V5 supports IPv6 addressing scheme and different authentication methods. This test suite can be used for testing security flaws and robustness of SOCKS proxy server implementations. The suite acts as a SOCKS client, and if wanted, it can act also as an application server, in which case an external application server is not needed. The test suite supports username-password authentication defined in RFC1929 and GSS-API authentication method defined in RFC1961. GSS-API authentication uses Kerberos v5 method.