To connect a laptop to a desktop using the USB ports, a bridge cable is needed. Bridge cables are proprietary, and using services over the connection often requires using the software that comes with the cable.
Bridge cables are identified by a hard plastic module between the two ends of the cable that contains the circuits that allow the two computers to communicate. Many such cables allow for two different types of connections: link mode, which only permits the two computers to transfer only data, and network mode, which allows the connected machines to share other network connections. It can also allow the laptop to use printers hooked up to the desktop. The software included with the cable must be running on both computers for the bridge service to work correctly. Using any other USB cable to attempt the bridge can cause damage to either computer, as USB cables also transmit power.