code: func DoTCPProbe(addr string, timeout time.Duration) (probe.Result, string, error) {
  	conn, err := net.DialTimeout("tcp", addr, timeout)
  	if err != nil {
  		// Convert errors to failures to handle timeouts.
  		return probe.Failure, err.Error(), nil
  	}
  	err = conn.Close()
  	if err != nil {
  		klog.Errorf("Unexpected error closing TCP probe socket: %v (%#v)", err, err)
  	}
  	return probe.Success, "", nil
  }
docs: // DoTCPProbe checks that a TCP socket to the address can be opened.
  // If the socket can be opened, it returns Success
  // If the socket fails to open, it returns Failure.
  // This is exported because some other packages may want to do direct TCP probes.