MonoDevelop - Can No Longer Attach Debugger

Completely out of the blue I can no longer attach MonoDevelop to Unity for debugging. I get the following error:

“Could not open port for debugger. Another process may be using the port.”

I have restarted my computer and opened nothing but Unity and MonoDevelop and I still get this error. I have been trying to shutdown processes that are listening on ports one-by-one but to no avail.

  • Does anyone know what port the debugger is attempting to use so I can figure out what process is conflicting with it?
  • Can I change the port that MonoDevelop is trying to use?
  • Is this an actual bug in MonoDevelop and has nothing to do with ports?

I found the problem. It seems I accidentally turned off the option to attach a debugger:

1414761--74209--$EditorAttach.png

Can be found under Edit->Preferences…->External Tools