VMware Serial Port Passthrough: The Definitive Guide
(2020 Edition)

Virtualization offers up the benefit of being able to simulate multiple environments with different operating systems, peripheral resources, and disaster recovery processes. With a single physical server, multiple virtual sessions can be created synchronously, allowing these virtual sessions to use and share the physical resources available on the server, whether it’s processing, storage or even accessing connected peripheral devices.

There is one shortcoming of virtualization environments, and that is the lack of VMware serial port support. There are however workarounds that can be implemented.

VMware serial port passthrough -
the easiest way

An easy and convenient way to redirect serial ports to VMware is to use Serial to Ethernet Connector (SEC). SEC allows you to share serial interface devices over both LAN and Internet.
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Accessing COM ports in VMware can be achieved by creating virtual copies of actual serial ports of the networked computers. These virtual serial ports are created within the VMware instance and through Serial Over Network, they are linked to the real COM port that they are emulating.

Once the connection is established, if a peripheral device is attached to the physical port on the server, the device will appear in the guest OS session and it will be accessible as if it is physically connected.

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How to add serial ports in VMware

In order to access serial ports within a VMware virtual machine, you need to follow these steps:

On the host server:

  1. Download and install the Serial to Ethernet Connector software.
  2. Start the application. In the “Server Connection” Tab, enter the host’s COM port to which the device is attached, as well as the TCP port to listen on.
  3. Click ‘Create server connection’.

On the guest operating system:

  1. Install the SEC Software, and then launch the application.
  2. Click on the ‘Client connection’ tab and specify the Host IP address and TCP port as defined in the host server.
  3. Enter a name for your virtual machine’s COM port and select the ‘Create as virtual serial port’ option.
  4. Click ‘Create client connection’.

Your client can now connect to the host’s COM interface via the virtual serial port over Ethernet connection created by SEC. The connected device on the COM port will be redirected to the virtual VMware serial port.

Forward serial ports to VMware Workstation

You can add up to 4 serial connections to VMware Workstation. This allows you to share different serial devices and make them available to the VM. The virtual interfaces that are created can redirect data to the physical serial ports, files or a named pipe. This is especially useful for debugging, where the virtual port can send data to the host or to other connected VMs.

Here is how to add serial ports in VMware Workstation:

  1. Shut down the virtual machine
  2. Select the VM and choose ‘VM > Settings”
  3. Select “Add” from the “Hardware” tab
  4. Select “Add Hardware” wizard and choose “Serial Port”
  5. Click “Finish”
  6. Select the destination of the serial port output
  • You can direct the output to the VMware host’s physical serial port.
  • Create a connection between virtual sessions or between a virtual session and the host with a named pipe.
  • Use any file on the host as an output file. You can create a new file or select an existing one by simply typing the name in the directory.
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If you have opted for a named pipe output, you’ll need to adjust your configurations according to your operating system as follows:

  • Linux Hosts

Add a UNIX socket name in the text box. The name must be the same on the client and the server and should look like this: /tmp/socketname

  • Windows host

You can enter a customized name or leave it as the default setting. The pipe name must be the same on both the client and the server, and it must follow the naming convention of \\.\pipe\.

When transmitting data between the server and the virtual machine, always configure the sender by selecting the “This End is the Server” option, and setting the receiver as “The Other End is the Application”.

If you want the VMware Workstation to connect to the serial port when the VM is turned on, select the “Connect at Power On” option.

Bear in mind when there are a number of virtual machines connected, the first VM will usually be the server.

Now to configure other VMs, simply repeat this process. If you are configuring the named pipe, you must define the client by selecting ‘This End is the Client”.

You’re now well on your way to redirecting serial ports in VMware. You can access different serial devices from any virtual session allowing you to have a wider, more valuable resource pool to share across your organization.