Problem
My service connects to a TCP server over a particular port and when establishing the connection throws the exception: “SocketException: Only one usage of each socket address (protocol/network address/port) is normally permitted”.
Diagnosing the Issue
Use netstat at the command line to see what is using the port.
netstat –a
Displays all the ports in use.
netstat –b
Displays all the active connections and the process/exe that is using them
In my case a network error had occurred and I believe my service had left the client open, knew it was dead and so was trying to reconnect – throwing the exception. Restarting the service resolved the issue but the code will need reviewing.
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