Remote check if machine is alive and reachable using c# under NAT

Question

I'm trying to develop a "backup service" that should start if i can't reach a specific pc.

The backup service should check if the machine is alive (ping isn't a solution because the remote machine can be natted).

Maybe a failed ssh connection can tell me if the machine is down\\not reachable.

The idea is:

 If (!EndPointIsAlive){
//start backup
}else{
//wait x and retry
}

Answer 1

NAT is no argument against ping as I stated in my comment. In my oppionion you try to re-invent the wheel. I advise you to check the SNMP protocol and SNMP traps, which fulfill just you needs.

Traps are trigger based events which are sent to a management machine, where an alarm is raised.

You would instantly know, if and which machine just went down.