With serial port redirection, you can redirect locally connected serial (/dev/ttyS) ports, such as built-in RS232 ports and USB-to-serial adapters. Devices such as printers, bar code readers, and other serial devices can be connected to these ports and used in virtual desktops and RDS-hosted desktops.

If an administrator has configured the serial port redirection feature, and if you use the VMware Blast or PCoIP display protocol, serial port redirection works in the virtual desktop or RDS-hosted desktop without further configuration. For example, /dev/ttyS0 on the local client system is redirected as COM1 on the remote desktop. Serial port /dev/ttyS1 is redirected as COM2. If the /dev/ttyS port is already in use, it is mapped to avoid conflicts. For example, if COM1 and COM2 exist on the remote desktop, /dev/ttyS0 on the client system is mapped to COM3 by default.

You must have any required device drivers installed on the local client system, but you do not need to install the device drivers on the remote desktop. For example, if you use a USB-to-serial adapter that requires specific device drivers to work on your local client system, you must install those drivers, but only on the client system.

Important: If you are using a device that plugs in to a USB-to-serial adapter, do not connect the device from the Connect USB Device menu in Horizon Client. Doing so routes the device through USB redirection and bypasses the serial port redirection feature.

Tips for Using the Serial Port Redirection Feature

  • Click the serial port icon ( Use the serial port icon to connect a serial port to the remote desktop ) in the system tray or notification area of the remote desktop to connect, disconnect, or customize the mapped /dev/ttyS ports.

    When you click the serial port icon, the Serial COM Redirection for VMware Horizon context menu appears. If an administrator has locked the configuration, the items in the context menu are dimmed. The icon appears only if an administrator has configured the serial port redirection feature and all requirements are met. For more information, see System Requirements for Serial Port Redirection.

  • In the context menu, the port items are listed as port mapped to port, for example, /dev/ttyS0 mapped to COM1. The first port, which is /dev/ttyS0 in this example, is the physical port or the USB-to-serial adapter on the local client system. The second port, which is COM1 in this example, is the port used in the remote desktop.
  • To select the Port Properties command, right-click a /dev/ttyS port.

    In the COM Properties dialog box, you can configure a port to connect automatically when a remote desktop session is started, or you can ignore DSR (data-set-ready signal), which is required for some modems and other devices.

    You can also change the port number that the remote desktop uses. For example, if the /dev/ttyS0 port on the client system is mapped to COM3 in the remote desktop, you can change the port number to COM1. If COM1 exists in the remote desktop, you might see COM1 (Overlapped). You can still use this overlapped port. The remote desktop can receive serial data through the port from the server and also from the client system.

  • Connect to a mapped COM port by selecting Connect to use the port in the remote desktop.

    When a redirected COM port is opened and in use on a remote desktop, you cannot access the port on the local computer. Conversely, when a /dev/ttyS port is in use on the local computer, you cannot access the port on the remote desktop.

  • You can then select the Disconnect command to disconnect and make the physical COM port available for use on the client computer.

Viewing Information About Redirected Serial Ports

For remote desktops that have Horizon Agent 2106 or later installed, you can view details about redirected serial ports by running the vmwsprrdctl.exe console utility on the desktop. The utility is supported on both remote desktop sessions and nested mode sessions.

The utility is located on the remote desktop in C:\Program Files\Common Files\VMware\SerialPortRedirection\Agent\vmwsprrdctl.exe.

To get help with command-line usage for the utility:

  1. Start a remote desktop session and open a console window on the desktop.
  2. Change to the directory location of the utility and run the following command.
    vmwsprrdctl.exe -h

The utility provides the following information.

  • Hardware ID information:
    • USB device VID (Vendor ID)
    • USB device PID (Product ID)
    • USB device Rev (Product Revision)
  • COM port device description as it appears in Device Manager
  • Source COM port number on the client
  • COM port redirection status
Note: The utility does not provide the source COM port number on the client or the COM port redirection status for any virtual COM port on the agent redirected from a client port that uses a USB-to-serial adapter.