The IsListening property returns True if the server is
listening for connections after the Start method has been
called. If the server has not been started, is not yet accepting
client connections or has been suspended, this property will return
False.
When a server is started, the control starts a background thread
which creates the listening socket and begins waiting for incoming
client connections. This property will only return True once the
server thread has started executing, so it may not return a value of
True immediately after the Start method has been called. To
determine the status of the server at any time, check the value of
the State property.