Very handy utility, but unfortunately the way MATLAB finds these serial ports does not take into account if other programs are using them - although fopen will of course prevent you from using that port. Also, when I incorporated it into a GUI, it did not stand up to being run a second time - it could not access the error message which instead replies with a 0x1 structure.
Shows available COM ports. When terminating a matlab program with CTRL-C. Windows 2000 thinks that the com port is occupied. Nice to se this in matlab. Can be seen by doing "mode" command at the command promt in windows as well.