USB Direct Connection


Since USB port is on every PC, is it possible to connect two PCs via USB ports using a USB cable?


Full Speed USB (USB 1.1) and High Speed USB (USB 2.0) specifications do not specify the use of a simple USB A-to-A cable for connecting two USB hosts. USB was designed to connect up to 127 USB peripherals to a USB host (typically a PC). It was not designed as a LAN technology and the USB Implementers Forum recommends existing LAN technology such as Ethernet for creating a computer network.

But maybe because users were interested in connecting computers using USB cable, many vendors worked out this "limitation" of USB specifications by making a special hardware, that's USB bridge or sometimes known as USB-to-USB adapter. A USB bridge emulates an NDIS-compliant LAN adapter. You can easily find an A-to-A USB cable with a USB bridge on the cable at computer or networking stores.

A-to-A USB cable with USB bridge

Figure: A USB bridge cable for USB networking.

The cable length is usually 2 meters and newer products support USB 2.0, so theoretically the USB bridge can transfer data at up to 480 Mbps, faster than the ubiquitous Fast Ethernet or even the pre-N Wi-Fi. Several vendors make USB bridge cable which can work in two modes, that's for simple data transfer between two computers and local area networking (LAN). If you want to copy or move large files from one computer to another, choose the direct transfer mode. If you want to network computers for file and printer sharing or Internet connection sharing, choose the virtual LAN mode.

To connect two computers (PCs) using a USB bridge in Windows XP:
- Install the software that comes with your hardware. It will copy the driver to your computer.
- Plug the USB bridge cable end to your computer' USB port.
- Follow the instructions on the Found New Hardware Wizard that appears to install the USB network adapter.
- Verify that the USB network adapter has been installed from the Device Manager.

USB virtual network adapter on the Device Manager

- A Local Area Connection will be created under LAN or High Speed Internet in Network Connections folder. You can use the Network Setup Wizard or define IP address and configure other settings manually via the Network Connections folder. The step-by-step instructions are similar with direct connection using Ethernet crossover cable. It includes defining computer and workgroup names, assigning private IP addresses and preparing files/folders, printer or Internet connection for sharing.
- If you find troubles when configuring the connection using Windows automatic private IP address assignment (DHCP), define a static IP address for each USB network adapter on each computer. Both IP addresses must be within the same subnet.
- If both PCs have USB 2.0 ports, you are going to have a 480 Mbps connection. If one PC has USB 1.1 port, the connection speed will fall to 12 Mbps.

USB 2.0 direct connection status


1. A-to-A USB cable has a type A USB connector at both ends. An A-connector is the rectangular connector that is plugged into a computer (USB host) or USB hub.
2. A USB bridge cable can also be used to connect a computer to a USB hub to create a LAN with more than two computers.
3. NDIS: Network Driver Interface Specification.

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