With serial port redirection, you can redirect locally connected, serial (COM) ports such as built-in RS232 ports or USB-to-serial adapters. Devices such as printers, bar code readers, and other serial devices can be connected to these ports and used in the remote desktops.

If a Horizon administrator has configured the serial port redirection feature, and if you use the VMware Blast display protocol or the PCoIP display protocol, serial port redirection works on the remote desktop without further configuration. For example, COM1 on the local client system is redirected as COM1 on the remote desktop. COM2 is redirected as COM2, unless the COM port is already in use. If so the COM port is mapped to avoid conflicts. For example, if COM1 and COM2 already exist on the remote desktop, COM1 on the client is mapped to COM3 by default.

Although you must have any required device drivers installed on the local client system, you do not need to install the device drivers on the remote desktop operating system where the agent is installed. 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. To do so routes the device through USB redirection, and bypasses the serial port redirection functionality.

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, and customize the mapped COM ports.

    When you click the serial port icon, the Serial COM Redirection for VMware Horizon context menu appears.

    Note: If the items in the context menu are grayed out, it means that an administrator has locked the configuration. Also note that the icon appears only if you use the required versions of the agent and Horizon Client for Windows, and you must connect over VMware Blast or PCoIP. The icon does not appear if you connect to a remote desktop from a Mac, Linux, or mobile client.
  • In the context menu, the port items are listed using the following format, for example: COM1 mapped to COM3. The first port, which is COM1 in this example, is the physical port or the USB-to-serial adapter used on the local client system. The second port, which is COM3 in this example, is the port used in the virtual desktop.
  • Right-click a COM port to select the Port Properties command.

    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 (that is, ignore the data-set-ready signal), which is required for some modems and other devices.

    You can also change the port number used in the remote desktop. For example, if the COM1 port on the client is mapped to COM3 in the remote desktop, but the application you are using requires COM1, you can change the port number to COM1. If COM1 already 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 ESXi host and also from the client system.

  • Make sure you connect to a mapped COM port before you attempt to launch an application that requires access to this port. For example, right-click a COM port and select Connect to use the port in the remote desktop. When you launch the application, the application opens the serial port.

    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 COM port is in use on the local computer, you cannot access the port on the remote desktop.

  • In the remote desktop, you can use the Windows Device Manager Port Settings tab to set the default Baud rate for a particular COM port. Be sure to use the same settings in the Windows Device Manager on your client system. Note that the settings from this tab are used only if the application does not specify the port settings.
  • Before you can disconnect the COM port, you must close the port in the application or close the application. You can then select the Disconnect command to disconnect and make the physical COM port available for use on the client computer.
  • If you configure a serial port to connect automatically, launch an application that opens the serial port, and then disconnect and resonnect the desktop session, the auto-connect feature does not work. You also cannot connect using the serial port's system tray icon's menu option. In most cases, the application can no longer use the serial port. This is expected behavior. You must terminate the application, disconnect the desktop session and reconnect again to resolve the problem.