# Unable to open COM port **URL:** \ **Category:** XCTU\ **Created:** [November 1, 2012, 12:07pm UTC](https://forums.digi.com/t/unable-to-open-com-port/3043 "2012-11-01T12:07:40Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![jdogjennings](https://avatars.discourse-cdn.com/v4/letter/j/2bfe46/32.png) [@jdogjennings](https://forums.digi.com/u/jdogjennings)\ **Post date:** [November 1, 2012, 12:07pm UTC](https://forums.digi.com/t/unable-to-open-com-port/3043/1 "2012-11-01T12:07:40Z")
I have a XBee-PRO-PKG U connected to a Windows 7 virtual machine running on a Mac and an XBee Pro module as the remote device (with a loopback jumper on the main In and Out ports. When I initially start X-CTU the Modem responds fine, i can read the parameters and write them as well. But when I do a range check it returns a message “Could not open COM port” Is this a problem with the hardware/software or is it an issue with running everything through a virtual machine? ---
**Author:** ![xainnasir](https://avatars.discourse-cdn.com/v4/letter/x/f14d63/32.png) [@xainnasir](https://forums.digi.com/u/xainnasir)\ **Post date:** [November 6, 2012, 12:56pm UTC](https://forums.digi.com/t/unable-to-open-com-port/3043/2 "2012-11-06T12:56:31Z")
I think its either the virtual modem error or there may be some error in ur hardware … its not the software one … first of all try it on real com port dont use usb to serial cable and then check ur hardware the output u r giving to the xbee … ---
**Author:** ![Ninad](https://avatars.discourse-cdn.com/v4/letter/n/7ba0ec/32.png) [@Ninad](https://forums.digi.com/u/Ninad)\ **Post date:** [March 7, 2013, 10:01pm UTC](https://forums.digi.com/t/unable-to-open-com-port/3043/3 "2013-03-07T22:01:56Z")
Is it true that you were trying to get the XTend modems to connect using a USB to serial connector at one end? If so, did you find a way to resolve the issue? I am facing the same problem and any inputs will be very helpful. Thanks!