How to monitor Systems Up or Down with ping disabled on them?

For security reasons, ping is disabled across servers in organization, Now in order to monitor system status (up/down) hence Heartbeat or Uptime are ruled out (as both work on ping mechanism) .
Currently a basic OS level monitoring of a process (systemd) being monitored i.e. if that process on these servers is running then server is up else down.
Now considering this scenario, I am seeking an advice on , If any one came across and implemented a workaround OR any expert advice would be of a real help .
Thanks in advance, looking for response and if any clarification please let me know .