Why can't I open more than one session to my serial port? - or can I?

[Believer]

Is there any way I can open more than one session to my serial port ASRL5::INSTR?

This is actually a big deal - because if my serial port is in use, and then another driver seeks to query my serial device it comes back as VI_ERROR_RSRC_BUSY - unfortunately popping up a horrible error message on the screen.

I thought the viOpen with an accessMode of VI_LOAD_CONFIG would work but I get the same result.

I have Visa 3.6 and am running Windows XP SP2

Thanks!

[Makoto]

I think it is due to restriction of Win32 kernel internals.  Once a process has opened a serial com port by CreateFile() or by similar file functions, any other processes can not open the device until it is closed.  The only exception is, it can be opened multiple times as shared access mode from within the same process.  Normally you can multi-open a file on HDD or CD-ROM from different processes at a time if in shared access mode, but not for serial com port device even if applying shared access.

[Wim S]

Hello,

I don't know if this is usefull information for your problem, but there are several programs that enable you to share a serial port between several applications.

http://www.serial-port-splitter.com/

http://www.mks.zp.ua/shared-serial-ports.php

http://www.shareup.com/Share_Serial_Ports-download-21220.html

[Believer]

"but there are several programs that enable you to share a serial port between several applications"

Thank you for the links - which I looked at. These take real COM ports and split them up.

However my serial port is actually a virtual serial port already - so I'm not sure if it would work.

But it is something to think about. Thank you.