Patrick, Problems with NAT devices are the only thing I can think of that might cause this problem. If a downstream LDM can make a TCP connection to port 388 on the upstream computer, then there shouldn't be any problem. Your saying that problems arise by keeping port 388 open but closing everything else makes no sense to me. If you close everything but incoming TCP connections to port 388 on the upstream computer, then does a notifyme(1) on a downstream computer to the upstream LDM work? Regards, Steve Emmerson Ticket Details =================== Ticket ID: RBX-213298 Department: Support NOAAPORT Priority: Normal Status: Closed