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I have a couple of servers that I'd like to duplicate as guest instances in virtualserver. One of the applications that runs on them uses the COM ports to communicate between the two servers, and specifically through null-modem/laplink/etc cable.

I've thought about binding the to guest instances COM ports to the host server's COM ports (1 and 2) and then connecting the ports together on with a null-modem cable. Is there a way I can make this connection entirely through virtualserver's control panel without having to physically access my server (it's cold and noisy in there :) )?

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VirtualBox does this out of the box. VirtualServer is kinda sucky IMHO – Tim Williscroft May 5 '09 at 2:57
up vote 2 down vote accepted

You can use a COM port redirector software to create virtual COM ports on both servers and connecting them by a TCP port. The linked Wikipedia page also provides links for both commercial and open source solutions.

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I have a solution that works under VMWare. it uses named pipe for serial communication between two VM. (Be advised that modem signals will not be carried across so hardware handshaking will fail).

Under VMWare you would do this:

On the "client side" add:

serial0.present = "TRUE"
serial0.fileType = "pipe"
serial0.pipe.endPoint = "client"
serial0.yieldOnMsrRead = "TRUE"
serial0.startConnected = "TRUE"
serial0.fileName = "/Virtual Machines/VMware/Serial/devbox_com1"

and this on the server side:

serial0.present = "TRUE"
serial0.fileType = "pipe"
serial0.yieldOnMsrRead = "TRUE"
serial0.startConnected = "TRUE"
serial0.fileName = "/Virtual Machines/VMware/Serial/devbox_com1"

This solution, of course does not apply exactly the same way for server 2005 but I would assume it should work (but I have not tested it).

Under Virtual Server 2005 follow these steps for both VM:

  1. Under Virtual Machines, point to Configure, and then click the virtual machine that you want to modify.
  2. Click the COM ports link.
  3. Under the serial port that you want to configure, click Physical computer serial port, and then click to clear the Wait for modem command to open port check box. Click Named pipe, and then type \.\pipe\name that you want to assign to the named pipe in the Named pipe box. For example, type \.\pipe\com2 and Click OK.

I must warn you that I never tried to get two named pipe setup under Virtual Server 2005 so I do not make guaranty.

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Just realized the question applied to Microsoft Virtual Server... oups! I leave the answer since I had to search a lot to get this. It will definitively not work in this case. – Pierre-Luc Simard May 4 '09 at 19:58

Using a remote terminal server like a Moxa ( is a common approach.

The serial devices all connect into the Moxa terminal server, then a windows Virtual COM port driver is installed on the VMWare Guest OS. The Virtual COM port driver is configured with the IP address of the Terminal server.

The advantage of this approach is that your virtual server becomes completely hardware independent, you can move the image around to any physical server, and as long as there's IP connectivity to your terminal server, nothing breaks.

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