TCP Socket error 105

I have made a simple app based on the tcp client / server example from the Xojo examples folder.
I set the tcp-socket server listening and send text with the client, it works great.

In order to extend a third party application that communicates by TCP socket, I set the Xojo app listing on that specific portnumber.
Directly after starting that app, my app reports error 105. This error is described as ‘No buffer space available’.

How do I create buffer space?

Where are you getting the error code from? TCPSocket.LastErrorCode = 105 means that the local port number is already in use.

If you need to accept several simultaneous connections on the same port then use the ServerSocket class, but you can’t use a port that’s being used by another app.

ok. the port is in use. that is correct. I have to use ServerSocket class.

The third party app is sending messages between differtent devices. I want to ’ hear’ / 'monitor ’ those messages too to do some extended actions in my software.