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Kepware Knowledge Base: Solution

Received Failure to start unsolicited communications Error Message

Last Update: 11/7/2018

The "Failure to start unsolicited communications" error message is posted to the KEPServerEX Event Log.

Possible Cause:
The Modbus TCP/IP Ethernet driver was unable to create a TCP socket with port 502 to listen for unsolicited Modbus communications.

In most cases, this error occurred because another application is running that has already created a TCP socket with port 502 on the same NIC that is being used in the KEPServerEX project. To resolve this error, shut down the other application or change the port number that the Modbus Master is using as well as the port number that the Modbus TCP/IP Ethernet driver is using to listen for unsolicited communications. This setting is located in Channel Properties | Ethernet.