Forum Index > [Comm32.ocx] Can't open Ports higher than 15

By: Guest Posted on: Jan 12 2011 at 08:23:28 PM
Hi there, Have just installed comm32 as having problems with mscomm32, but it still will not allow a comm port higher than 15 to be opened. I have a comm port 30 which when I put the number 30 into the comm port number the device ID shows up ok but when I open the port it says invalid port number. If I change the comm port number to a lower number in device manager then it will open it ok. I am using VB6. Is this a restriction of the trial version of Comm32 or am I doing something wrong? Don't want to buy it if its going to have the same problem as MSComm32.ocx

By: Guest Posted on: Jan 12 2011 at 08:27:32 PM
Sorry to add to this, the function portexists shows that the port does exist. Am also running on Windows 7. Any help greatly appreciated. :-)

By: Support Posted on: Jan 12 2011 at 10:11:50 PM
No, there's no such restriction in the trial version.

You should not have any problem opening ports above 15

Try the getPortStatus function. What does that say?

By: Nick Smith Posted on: Jan 13 2011 at 12:18:01 AM
Hiya and thanks for the fast response, impressive!

There doesn't seem to be a function for getPortStatus but I may have solved the problem in the meantime. I had to reset all the port numbers from system registry and restart the machine and now it seems to talk to higher numbers ok. If I reassign a comm port number from device manager then I have to restart the computer otherwise it will not open the port.

Another question, MScomm32 had a memory leak which if the commport was opened and closed repeatedly over a few days the program would hang, is this a problem that is known and is it fixed in comm32? If so then that would seal the deal for me and will save me re-writting whole sections of comms routines.

Praying that this is something that is fixed...

Many thanks again and look forward to your reply. :-)

By: Support Posted on: Jan 13 2011 at 02:49:07 PM
During testing and development I often use device manager to change the port numbers. I've never needed to do it via the registry. Changing via device manager the changes take affect immediately.

getPortStatus function appeared around October 2010 with version 3.2t (See the version property)

The portexists function simply returns true or false but the getportstatus function returns a numerical value indicating the reason if the port is not available.

Memory leak. Microsoft say the memory leak in their MSComm32 can be reproduced simply by doing something like this:-


Open the port

pause a moment

close the port

pause a moment


They say that if you let that run for a while you'll see the memory drain - although I do believe Microsoft fixed their bug in more recent VS SP's

I've never been aware of any such bug in our OCX but please do run that test and let us know. If you find such a bug then I assure you we'll give it our immediate attention.

By: Nick Smith Posted on: Jan 16 2011 at 11:15:23 PM
Thank you once again for your very prompt reply. I have been running your control on 7 open ports for 4 days now and not one hiccup, very impressive. Have now bought the control as it is a bargain especially compared to the hastles MSComm32 gave me, thank you for a great improvement on MScomm32, one very happy customer and am happy to recommend to anyone! :-)


Reply - add comment to this topic
You may enter letters, numbers and standard punctuation only. HTML and other scripts/tags will be rejected
  Topic:- [Comm32.ocx] Can't open Ports higher than 15

Your Name


Forum scripts and databases - Copyright (c) 2009 - 2012