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Configure a COM port for a virtual machine

Updated: June 25, 2009

Applies To: Windows 7

The COM ports on a virtual machine provide serial connections. This type of port is most commonly used to transfer data for debugging purposes or to capture the output of virtual machine. You can select one of the following to attach to a COM port:

  • Physical serial port. Select this option to use a COM port on the physical computer for input and output on the virtual machine. If you want the serial port on the physical computer to be captured when a program running on the virtual machine attempts to access the COM port, select Wait for modem command to open port. This option causes Windows Virtual PC to wait for an AT modem command to be sent for the port (AT commands direct the modem to perform communication tasks). If the program using the COM port times out after capturing the port, the port is released to the host operating system.

    Clear this option if you want the virtual machine to attempt to capture the serial port on the physical computer when the virtual machine starts. If the serial port is already captured, the virtual machine cannot capture it. If the virtual machine captures the serial port, the serial port is not released to the host operating system until the virtual machine is shut down.

  • Named pipe. This option connects the virtual serial port to a Windows named pipe on the host operating system or a computer on the network. A named pipe is a portion of memory that can be used by one process to pass information to another process, so that the output of one is the input of the other. The second process can be local (on the same computer as the first) or remote (on a networked computer). For example, a local named pipe path could be \\.\pipe\mypipename.

    Named pipes can be used to create a virtual null modem cable between two virtual machines, or between a virtual machine and a debugging program on the host operating system that supports the use of named pipes. By connecting two virtual serial ports to the same named pipe, you can create a virtual null modem cable connection. Named pipes are useful for debugging or for any program that requires a null modem connection.

  • Text file. Select this option to send COM port output from the virtual machine to a text file. You can specify a text file location on any valid disk drive on the physical computer.

To configure a COM port for a virtual machine

  1. Open the settings for the virtual machine. Do one of the following:

    • In the Virtual Machines folder, right-click the name of the virtual machine, and then click Settings.

    • From the virtual machine window, click the Tools menu, and then click Settings.

  2. In the left pane of the Windows Virtual PC Settings page, click the name of an available COM port. For example, COM 1.

  3. In the right pane, select the type of connection you want to make and provide the additional details. For example, specify the full path and name for the named pipe or text file.

  4. Click OK to save the change.

See Also

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