The MaxPort property specifies the maximum range of port
numbers that will be used with passive data connections. A value of
zero specifies the default value of 65535 should be used. The minimum
value of this member is 10000 and the maximum value is 65535. If the
value is non-zero, it must be greater than the value of the MinPort
property.
Attempting to change the value of this property after the server
has started will cause an exception to be raised. To change the
maximum port number for the server, you must first call the Stop
method which will terminate all active client connections.