Simple Modbus channels are able to use either one or two communication ports, depending on your system setup. Communications can be either Serial or TCP/IP. Where Network communications are used, Modbus channels use Modbus Transmission Control Protocol (TCP).
Use the Connection Type field on the Primary Port and Secondary Port tabs to specify how many ports are available for a channel, and the type of connection that is used. Where a Serial connection is specified, you need to specify the properties for that connection. For further information, see Configure a Channel’s Serial Connection Properties in the Geo SCADA Expert Guide to Drivers.
For an example that uses a channel with a Modbus TCP connection, see Use Modbus RTU to Communicate via a Terminal Server.