code: func (c *Client) ListenTCP(laddr *net.TCPAddr) (net.Listener, error) {
  	if laddr.Port == 0 && isBrokenOpenSSHVersion(string(c.ServerVersion())) {
  		return c.autoPortListenWorkaround(laddr)
  	}
  
  	m := channelForwardMsg{
  		laddr.IP.String(),
  		uint32(laddr.Port),
  	}
  	// send message
  	ok, resp, err := c.SendRequest("tcpip-forward", true, Marshal(&m))
  	if err != nil {
  		return nil, err
  	}
  	if !ok {
  		return nil, errors.New("ssh: tcpip-forward request denied by peer")
  	}
  
  	// If the original port was 0, then the remote side will
  	// supply a real port number in the response.
  	if laddr.Port == 0 {
  		var p struct {
  			Port uint32
  		}
  		if err := Unmarshal(resp, &p); err != nil {
  			return nil, err
  		}
  		laddr.Port = int(p.Port)
  	}
  
  	// Register this forward, using the port number we obtained.
  	ch := c.forwards.add(*laddr)
  
  	return &tcpListener{laddr, c, ch}, nil
  }
docs: // ListenTCP requests the remote peer open a listening socket
  // on laddr. Incoming connections will be available by calling
  // Accept on the returned net.Listener.