SOCKS4

SOCKS4 is a predecessor of SOCKS5. Like its successor it works at the transport layer and forwards traffic without understanding the application protocol, but it is far more limited: it handles only TCP, offers no authentication, and the original version could not resolve hostnames — the client had to pass an IP address. A common extension, SOCKS4a, added remote hostname resolution. Because it lacks authentication and UDP, SOCKS4 has been almost entirely superseded by SOCKS5 for modern use.

A SOCKS4 client connects to the proxy and sends a request containing the target IP and port plus a user-ID string; the proxy opens the connection and relays bytes. Without an authentication exchange, access control has to come from elsewhere — typically IP whitelisting. There is no UDP association, so UDP-based traffic cannot pass. The destination still sees the proxy's exit IP rather than your real address, which is the one property it shares fully with newer proxies.

s4m provides an authenticated SOCKS5 proxy on port 1080 rather than SOCKS4. SOCKS5 supports username/password negotiation and defines UDP ASSOCIATE, but authentication alone does not encrypt credentials or payloads, and UDP needs end-to-end support. Use a SOCKS5-capable client and TLS for sensitive application traffic. See the s4m proxy plans. The free public proxy list is a separate third-party pool: its protocol and anonymity labels are test results, not a guarantee of safety.