How to know why OpenEx() chose these specific ports?

I have this method call:

OpenEx( "DSN=MyServer; UID=foo; PWD=bar", dwOptions ); // dwOptions = 12

OpenEx method is overloaded from CDatabase, and inside our version I have this call:

if ( !Connect( dwOptions ) )

Once the above gets executed and succeed, a connection gets established using some port within the range 5xxxx.

Reading on CDatabase, Connect() is no longer there.

I need to know on what criteria did this Connect() choose the 5xxxx range, was it random? pre-configured somewhere? Can I change it?

Help.