While testing a simple tornado app I managed to get a WinError 10048. The rest of the error message made no sense which is why I’ve made a note of it here.
Basically is was caused by the port I had tried binding to already being in use. In my case a previous run had failed to exit. When I tried to run the program again I got this message. A simple mistake and easy to fix.
If you do need to check what applications are listening on ports use the netstat command with as follows