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Kepware Knowledge Base: Solution


Resolving 'Communications error on COMn [***O***]'


Last Update: 11/12/2018

Possible Cause:
This is a character buffer overrun error.

Solution:
To resolve the error, refer to the instructions below.

  1. Open the Windows Device Manager. Then, click Ports | <the COM port in question> | Port Settings | Advanced.
  2. Next, decrease the Receive Buffer one notch from the maximum.
  3. Restart the computer. The new setting will not take effect until the computer has been restarted.
  4. Continue to decrease the Receive Buffer until the buffer overruns stop occurring.

Note: Do not automatically set the Receive Buffer to 1. It needs to be as high as possible without causing buffer overruns.

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KEPServerEX