What causes "request version:%d error" in XX-net/XX-Net?

Set the client to SOCKS5: socks5://127.0.0.1:

request version:%d error

Error message

request version:%d error

What it means

Logged by X-Tunnel's socks5_handler when the request frame's version byte is not 5 (e.g. 4 for SOCKS4). The handler refuses the request and closes the connection. Note the preceding debug line referencing auth_mode_num/data is leftover from the greeting stage and will itself often fail with NameError on that path in strict review — the effective signal is the non-5 version.

Source

Thrown at code/default/x_tunnel/local/proxy_handler.py:239

        g.session.conn_list[conn_id].start(block=True)

    def socks5_handler(self):
        sock = self.connection
        auth_mode_num = ord(self.read_bytes(1))
        data = self.read_bytes(auth_mode_num)

        sock.send(b"\x05\x00")  # socks version 5, no auth needed.
        try:
            data = self.read_bytes(4)
        except Exception as e:
            xlog.debug("socks5 auth num:%d, list:%s", auth_mode_num, utils.str2hex(data))
            xlog.warn("socks5 protocol error:%r", e)
            return

        socks_version = ord(data[0:1])
        if socks_version != 5:
            xlog.warn("request version:%d error", socks_version)
            return

        command = ord(data[1:2])
        if command != 1:  # 1. Tcp connect
            xlog.warn("request not supported command mode:%d", command)
            sock.send(b"\x05\x07\x00\x01")  # Command not supported
            return

        addrtype_pack = data[3:4]
        addrtype = ord(addrtype_pack)
        if addrtype == 1:  # IPv4
            addr_pack = self.read_bytes(4)
            addr = socket.inet_ntoa(addr_pack)
        elif addrtype == 3:  # Domain name
            domain_len_pack = self.read_bytes(1)[0:1]
            domain_len = ord(domain_len_pack)
            domain = self.read_bytes(domain_len)
            addr_pack = domain_len_pack + domain

View on GitHub (pinned to cfa5bc17b6)

Solutions

Set the client to SOCKS5: socks5://127.0.0.1:<port>
Confirm the application is connecting to the X-Tunnel local port, not another service
Remove the stale debug line referencing undefined auth_mode_num/data in the except block to avoid masking the real error

Example fix

# before
except Exception as e:
    xlog.debug("socks5 auth num:%d, list:%s", auth_mode_num, utils.str2hex(data))
    xlog.warn("socks5 protocol error:%r", e)

# after
except Exception as e:
    xlog.warn("socks5 protocol error:%r", e)

Defensive patterns

Strategy: validation

Validate before calling

# client side
assert proxy_scheme == 'socks5', 'X-Tunnel local proxy is SOCKS5 only'

Prevention

Use socks5:// in client configuration
Remove the stale debug line in the except block so real errors surface

When it happens

Trigger: A SOCKS4 client or a non-SOCKS protocol sends bytes to the X-Tunnel local SOCKS5 port after the initial greeting exchange.

Common situations: Client proxy configured as SOCKS4 instead of SOCKS5, wrong port targeted by another application, protocol garbage from port scans.

Related errors

AI-assisted analysis of XX-net/XX-Net@cfa5bc17b6 (2026-08-27). Data as JSON: /api/errors/c9f24b0c71d7e476. Report an issue: GitHub.