Possible results are
0 - Success, connection to target was established and expected response was received.
2 - Can not connect to target (connection refused or connection timeout)
3 - Invalid / unexpected response from target (e.g. pattern or response-code not matched)
4 - Agent internal error
5 - Protocol handshake error (e.g. wrong data or no data expected by protocol received, SSL certificate problem)
(https://www.netxms.org/documentation/adminguide/service-monitoring.html#network-service-monitoring-using-dci)
Value of 1 is not described there :), but yes, that's bad parameters of the metric