ginuerzh/gost · error

Service unavailable

Error message

Service unavailable

What it means

Returned by the SOCKS5 bind connector's ConnectContext (socks.go) when the SOCKS5 server replies to the BIND request with a Rep code other than Succeeded. The error is client-side reporting of a server-side rejection: the proxy accepted the connection but refused or failed to set up the bind listener.

Source

Thrown at socks.go:276

	if err := req.Write(conn); err != nil {
		return nil, err
	}

	if Debug {
		log.Log("[socks5]", req)
	}

	reply, err := gosocks5.ReadReply(conn)
	if err != nil {
		return nil, err
	}

	if Debug {
		log.Log("[socks5]", reply)
	}

	if reply.Rep != gosocks5.Succeeded {
		return nil, errors.New("Service unavailable")
	}

	return conn, nil
}

type socks5BindConnector struct {
	User *url.Userinfo
}

// SOCKS5BindConnector creates a connector for SOCKS5 bind.
// It accepts an optional auth info for SOCKS5 Username/Password Authentication.
func SOCKS5BindConnector(user *url.Userinfo) Connector {
	return &socks5BindConnector{User: user}
}

func (c *socks5BindConnector) Connect(conn net.Conn, address string, options ...ConnectOption) (net.Conn, error) {
	return c.ConnectContext(context.Background(), conn, "tcp", address, options...)
}

View on GitHub (pinned to a33fdbf4c9)

Solutions

1. Inspect the SOCKS5 server logs to find why the BIND request was rejected
2. Verify the target address/port passed in the bind request is reachable and permitted by the proxy's ACL
3. Confirm the SOCKS5 server supports the BIND command at all
4. Check that authentication succeeded — some servers report auth failures as a generic non-success Rep

When it happens

Trigger: Thrown at socks.go:276 when the library encounters an invalid state.

Common situations: See trigger scenarios.

Understand the failure class

• HTTP status errors: handling 4xx and 5xx responses — how to handle 4xx and 5xx responses properly.

AI-assisted analysis of ginuerzh/gost@a33fdbf4c9 (2026-09-02). Data as JSON: /api/errors/2548d83eea0cd858. Report an issue: GitHub.