The PLC compatibility problem
A plant may add Ethernet gateways, serial device servers, DTUs, or remote access equipment while the Windows PLC software still expects COM1, COM2, or another serial port. Replacing the software may be more risky than bridging the connection.
How a virtual serial port helps
The bridge presents a local COM port to the PLC software and forwards traffic to the TCP endpoint. This keeps the software interface stable while allowing the physical connection to move over Ethernet.
Before you configure the bridge
- Record the PLC gateway IP address and TCP port.
- Confirm whether the gateway expects raw TCP or another transport mode.
- Check the serial settings used by the PLC software and device.
- Choose a COM number that operators can recognize and document.
Recommended test sequence
- Ping or otherwise verify network reachability from the Windows machine.
- Create the virtual COM port in the bridge software.
- Add a TCP client binding to the PLC gateway.
- Start the binding and check for connected status.
- Open the virtual COM port in the PLC software and run a read-only test first.
Reliability notes
For unattended PLC workflows, use reconnect behavior and keep a record of the COM number, IP address, port, and protocol mode. This makes future troubleshooting much faster.