ps ef| grep drp
If you see an entry for each Digi Device similar to the following, the RealPort process is running.
root 2254 1 0 Dec 13 ? 0:03/sbin/drpd 1 199.86.0.1 root 2049 1 0 Dec 13 ? 0:01/sbin/drpd 1 199.86.5.1
/usr/sbin/drpadmin