While using amazon gamelift and UNet LLAPI, how to return the proper listening Port to gamelift?

While using amazon gamelift and UNet LLAPI, how to return the proper listening Port to gamelift, and what's the standard process?

If I return port by getting free ports, should I keep the unet server running continuously? Because if a process considers a particular port 'x' for it, 'x' should appear as busy for another process. So this needs unet server's host to be continuously running. Am I right?

If I keep running host continuously, how to disconnect all connections of a host after a session ends?

If above process is wrong, what's the correct process (or better process if any) for returning port while using UNet and gamelift?