Download of Image File

I want to download a new image file to the device but the Kernel Download Tool or the Windows CE Platform Builder doesn't response to the Bootme request. Why can the download not work although I can ping the emtrion...
The device requests a new image from a workstation by sending a bootme message as an ethernet broadcast to the connected network. This ethernet broadcast with the destination FF:FF:FF:FF:FF:FF is a UDP datagram on port 980 (dec.). So if this port 980 is blocked by an active Windows-Firewall, the download doesn't start. Furthermore the download will also not start when a router instead of a network switch or a direct cable is connected between the device and the workstation because ethernet broadcasts are normally not routed between two networks.