XTLS/Xray-core · error

set deadline: %w

Error message

set deadline: %w

What it means

Wraps a failure from deadlines.beginHandshake(), which sets the socket's read/write deadlines at the start of the Minecraft login handshake. The %w chains the underlying net.Conn.SetDeadline error, typically indicating the connection is already closed or the OS refused the deadline (e.g. invalid deadline on a wrapped conn).

Source

Thrown at transport/internet/finalmask/xmc/client.go:79

		profiles:        profiles,
		password:        password,
		rsaPublicKey:    rsaPublicKey,
		hostname:        hostname,
		paddingSchedule: paddingSchedule,
		deadlines:       newConnectionDeadlines(c),
	}, nil
}

func (c *clientConn) handshake() error {
	c.handshakeLock.Lock()
	defer c.handshakeLock.Unlock()

	if c.state != clientStateHandshake {
		return nil
	}

	if err := c.deadlines.beginHandshake(); err != nil {
		return fmt.Errorf("set deadline: %w", err)
	}
	defer func() { _ = c.deadlines.endHandshake() }()

	var (
		protocolVersion Varint        = Varint(775)
		serverAddress   String        = String(c.hostname)
		serverPort      UnsignedShort = UnsignedShort(25565)
		nextState       Varint        = Varint(2)
	)

	host, portString, err := net.SplitHostPort(c.c.RemoteAddr().String())
	if err == nil {
		port, err := strconv.Atoi(portString)
		if err == nil {
			serverPort = UnsignedShort(port)
		}

		if serverAddress == "" {

View on GitHub (pinned to 7d214f8b09)

Solutions

1. Check that the remote address/port is correct and the server accepts connections.
2. Unwrap the error (errors.As to *net.OpError) to see whether it is 'use of closed network connection' or a timeout.
3. If using a custom net.Conn wrapper, make sure SetDeadline is implemented rather than returning an error.

if err := cc.Handshake(); err != nil {
	var opErr *net.OpError
	if errors.As(err, &opErr) && opErr.Op == "set-deadline" {
		// conn already dead or wrapper lacks deadline support
		_ = conn.Close()
		return retryDial(ctx)
	}
	return err
}

When it happens

Trigger: Calling handshake() on a conn that the peer already closed, or on a custom net.Conn wrapper whose SetDeadline returns an error. Timeout enforcement begins here, so dead conns surface at this point rather than at the first write.

Common situations: Server closed the TCP connection during a previous phase; aggressive server-side connection timeouts; passing a pipe or mock conn into the transport without deadline support.

Related errors

• select padding profile: %w
• write handshake packet: %w
• write login start: %w
• read encryption request: %w
• bad encrypt request packet id

AI-assisted analysis of XTLS/Xray-core@7d214f8b09 (2026-08-15). Data as JSON: /api/errors/de6e356659c6c509. Report an issue: GitHub.