PLC5 Messaging Across A Router

Hi,
I have PLC5's at our main site and at a remote pumping station. Routing is set up across ISDN to allow me to access the remote PLC's from the main site SCADA LAN. I can ping the remote LAN, interrogate the remote PLC's and access a remote SCADA using remote desktop or VNC but I can't get PLC5 messaging to work between the two sites to fire some alarn klaxons and bring in some analogue values I'm interested in. Before I increased the message connect timeout and message reply timeout settings in the PLC on the main site I was getting a comms timeout error in the MSG block but now the MSG block sits enabled but doesn't complete the read, no errors are generated. Any ideas ?

Cheers
Jim

First make sure that the Default Gateway address in the PLC-5E itself is the correct address of the router that leads to the remote network.

PING and HTTP and RDP are well-known protocols that most firewalls and routers handle gracefully. The PLC-5 MSG instructions operate on TCP Ports 2222 (native PLC5) and 44818 (Multi-Hop Mode).

Try the TCPING utility to make sure that those two ports are being handled correctly by your router.

If neither of those approaches shows useful information, you're going to need to find a mirror port to sniff the Ethernet data stream.

Thanks Ken,
The main site PLC gateway address is different but I'm going to need to wait for a plant shutdown to change it. Let you know how I get on.

Jim