Hello Pierre
Welcome to the forum.
There are a number of things it might be, but my first guess is that you should check the IP address. If you used ipaddy, it would have told you your "public" address. That is, the IP address your router has on the internet.
That will usually be different from the local IP address on your local network.
The PCs (etc) on the local network are allocated an address by the router, something link 192.168.0.10, for example. If you are connecting from one PC on your local network to another on that network, you would use the local address.
You can find out the local address by going to Start / Run / CMD, then typing the command IPCONFIG /ALL (it does not need to be in capital letters, I just typed it that way to illustrate the command). It will tell you the IP Address of the local connection. It's the address of the PC running broadwave that you need to type into here: http://myipaddress:88/broadwave.asx?src=1&kbps=56. Note the http:// in front of it - some players are fussy. Also make sure port 88 is open on the Broadwave PC's firewall, if any.
Once you get it working locally, you can then try via the internet, and you need to open the port and set up redirection on your router - but that's for another reply!
Good luck, let us know how you get on.