Communicating to control networks via the internet


Thread Starter

Kirby, Brendan

Hello Ball, (making an address)

I wish to communicate to a Modbus/TCP to Modbus RTU Converter (Lantronix's Cobox) from an NT based Cimplicity program over the internet. This means that on the Controller/PLC side I will be connected to a corporate LAN that has one IP address as seen by the Internet. The converter (call it a gateway) will look like a web "client", it will not be initiating a connection. From the little knowledge that I have it seems that the internet router on my "gateway" LAN will have to be configured to except the unique TCP port number and reroute this to the unique LAN address of the gateway using the NAT funcunality of the router. Does this make sense (meaning do I
need to read up on the router configuration and define a static table)? How about if I need multiple gateways? How much of a security issue is this? Any good books out there that I should be buying on this subject? Is this the future (present)?

____ LAN ____ internet _____ LAN ____ Modbus RTU __
| |___ | |________| |__ | |_________ |
|____| |____| |_____| |____| |__
PC w/ Router Router Gateway PLC

thnks in advance,

brendan kirby
acrison inc

Rob Entzinger

You configure the Lantronix Cobox with the TCPIP address, Modbus RTU parameters and the mode (master/slave etc.) Away you go for the PLC interface. The internet area will depend on your