I have a memory leak (I think), so it seems best to restart my server from time to time.
(about 1-2 times per week).
What I noticed was sometimes when I shut it down,
and then started it up again, I could not connect from a client,
even though Union Admin always could.
Occasionally it would be fine the first time,
or maybe the second, or maybe the third,
but sometimes it seemed the only thing to do was
reboot the operating system. (Which is not a problem,
because Union is the only thing running on it anyway.)
But now I think I have found the magic formula to getting it to
come up after just stopserver.sh (or stop server button in
Union Admin) followed by startserver.sh.
And that, very simply, is to wait 10-15 seconds between them,
for everything (I don't know what exactly, but probably network
stuff) to settle down or get cleaned up.
Since I started being a little more patient, it comes back to full life
on the first try just about every time.
I just thought I'd pass that little tip along if anyone else was seeing
the same thing.