Generic USB redirection of Serial ports is supported in UXP and RDP sessions.

Note: In RDP sessions the Generic USB redirection should only be used when the applications fail to communicate with the serial device through the serial port redirected in Native way.

When the Generic USB redirection will be used for the serial ports then the low-level USB communication between the USB-to-serial adapter and virtual USB hub assigned to the user session on the terminal server machine will be sent over the terminal connection.

Some USB-to-serial adapters (e.g. the Prolific PL2303-based one used to illustrate examples contained in this book) appear on the USB bus as Vendor Specific Class devices. The RX-series firmware is unable to recognize such USB-to-serial adapters as serial ports. To enable the Generic USB redirection of such adapters their VID and PID numbers need to be added to the Custom VID:PID list.

The USB-to-serial adapter redirected with Generic USB redirection will appear in Device Manager of the terminal server machine. The ‘change port’ command can also be used inside the UXP or RDP session to verify whether the serial port has been redirected properly. Command output similar to the below will confirm a successful redirection:

Note: Additional requirements and limitations apply when using the RDP protocol.

Optimizing the Generic USB redirection of serial ports in vSpace Pro systems

The drawback of the Generic USB redirection is the fact that the Windows OS can create the redirected serial ports using unpredictable numbers (COM9, COM11, …) The same user connecting from the same device can get during subsequent logon differently numbered serial ports. Users connecting to same multiuser terminal server machine will surely get differently numbered serial ports. This can constitute a serious administrative challenge and make the configuration of application software installed on the terminal server difficult. The vSpace Pro 11LST and vSpace Pro Enterprise Edition system contain the ‘COM port management’ feature which allows mitigating the above described issue.

The number used for the first redirected COM port can be selected in vSpace Console, under ‘Servers > Server > Settings > Peripheral Devices’:

With this feature enabled the serial ports redirected from vSpace Client devices will be created starting with the selected number (e.g. COM3). All users of the vSpace Pro server (even connected concurrently) will get the redirected serial ports with the selected name. This will greatly simplify the configuration of the application software which will need to access the serial device, as the same system-wide settings can be used for all users.

Native redirection of Serial ports is supported in RDP connections only.

The RX-RDP, RX420(RDP), RX300 and LEAF OS firmware contain drivers for numerous USB-to-serial adapters, including adapters based on the popular Prolific PL2303, FTDI, CH341 chips, among many others. The device firmware creates a local serial port which the RDP client redirects then in the functional way.

The ‘change port’ command can be used inside the RDP session to verify whether the serial port has been redirected properly. Command output similar to the below will confirm a successful redirection:

The serial port redirected with native redirection will not appear in Device Manager of the remote desktop server.