server.pl doing nothing when network comes back after going down

I used this programs for a while. It’s working well at first, and give a headache later.
The story is that I sometimes saw that all the server.pl processes are doing nothing, and Nagios sent notifications for each service with UNKNOWN status.
Later I figured out that whenever the network is down, all the server.pl processes lost connection but still running. When the network comes back up, those processes cannot gain the connections.