Android : At what point does Android free ports?

I have a child activity that creates an asynchronous task that opens a Java ServerSocket and calls accept() on that serverPort.

Now, in this Activity's onStop() method, I have a call to cancel() my asynchronous task. In my asynchronous class, in both the onPostExecute() and onCancelled() methods, I close the serverSocket (as well as any other dataStreams or Sockets that may have been opened).

All my code runs properly. Through debugging, I know for a fact that if I:

1. Run the application linearly up to the point where the serverSocket starts to accept() connections.


2. Hit the back button, closing the child activity and calling its onStop() method which then cancels the asynchronous task in question and calls close() on the serverSocket.


3. Run the child activity again, creating the new Asynchronous thread, and the code runs up to the point where I create a serverSocket on the same port as the first one. However, it throws an IO exception and says that the port is already in use.


4. 
   

   No matter how long I wait restarting this child Activity will just shoot off IO exceptions claiming that the port is already taken. However, doing things like:

   
   

   Restarting the device

   
   

   Reinstalling the Application

   
   

   Completely Closing the Application (instead of just relaunching the child activity from its parent activity)

   
   

Seem to free up the port.

How exactly does Android refresh/free up ports that you've used? Is there any way I could call a refresh on those ports programatically?

And before the obvious questions arise, I'm using P2P and java sockets, so yes, I do actually want to use direct connection to sockets and direct accept on static local ports and the such.

EDIT: formatting