Multicast port is now configurable.

[JasonMahdjoub]

I use Cling in order to detect the local UPNP router of the lan, and to ask it to open a port with the current computer. I have made some tests, and they work under Linux and under Windows. However, I can't do these tests under MacOS. Here the log of Cling :

org.fourthline.cling.UpnpServiceImpl INFOS : >>> Starting UPnP service...
org.fourthline.cling.UpnpServiceImpl INFOS : Using configuration: com.distrimind.madkit.kernel.network.DefaultUpnpServiceConfiguration
org.fourthline.cling.transport.Router INFOS : Creating Router: org.fourthline.cling.transport.RouterImpl
org.fourthline.cling.transport.spi.MulticastReceiver INFOS : Creating wildcard socket (for receiving multicast datagrams) on port: 1900
org.fourthline.cling.transport.Router GRAVE : Unable to initialize network router: org.fourthline.cling.transport.spi.InitializationException: Could not initialize MulticastReceiverImpl: java.net.BindException: Address already in use
org.fourthline.cling.transport.Router GRAVE : Cause: org.fourthline.cling.transport.spi.InitializationException: Could not initialize MulticastReceiverImpl: java.net.BindException: Address already in use
org.fourthline.cling.UpnpServiceImpl INFOS : <<< UPnP service started successfully

It appears that the port 1900 is officially used by "Back to my mac" on mac OS. But if I make a netstat ou a lsof, no port is opened.

I have read the code, but there is no possibility to change the multicast port. So I have changed the code to enable it. It does not produce regression and it enables me to open another port than 1900. Then, with these modifications, I can open a port with my UPNP router.

So I propose you to accept this pull request.

Best regards,

Jason.