Determining what is using the Serial Port - PLCS.net

bbopn · May 30th, 2008, 04:52 PM

About a month ago I was at a customer's jobsite and used Mdbus Modbus simulator while troubleshooting some DCS problems. I connected to the ProSoft Modbus Card via my Latitude D830 serial port (COM1) without issue and even connected to a Woodward Governer and 489 Multilin... all via the COM1 port.

Earlier this week a co-worker wanted to do some Modbus simulation and asked if I would set up my computer to be a Slave and he would set his up to be the Master. When I tried turning the Mdbus simulator "On", it gave me a message that said it couldn't open the comm port.

I then ran RSLinx opened my drivers and attempted to start the DF1 driver. It gave me a message similar to what Mdbus and the DF1 status had a "Port Conflict" on it.

I realized then that something had grabbed control of my COM1 port and attempted several things like turning services OFF, uninstalling some programs I had loaded up since the last time the COM1 port worked. This did not yield anything.

I then went into my BIOS and changed the comm port to COM2 and the on board comm port is now working.

My question is this.... Is there any program that can help you determine what is taking control of the serial comm port? I did a cursory Google search and didn't come up with much. AB's knowledge base wasn't much help either. It said to close the application that was using the comm port.... which I would do IF I knew what application was using it.

Any direction on this would be greatly appreciated. Even though I have my serial port back by reassigning it to COM2, I feel like this is a cheesy fix and would like to determine what is taking control of the comm port.

Thanks,
Bobby

danw · May 30th, 2008, 05:55 PM

I have searched in vain for the utility that would report what has taken possession of the COM port without success. If you discover such a thing, would you be sure to tell us?

The only thing I can think of is to take a screen shot of task manager (for a record of the list or running apps), then do the laborious task of figuring out which running app could grab the serial port. If you're like me, you won't know what most of them do, so it'll be the Google-the-executable-file-name-effort to see what comes up.
Dan

gmferg · May 30th, 2008, 06:26 PM

I've had a similar thing happen to me on occassion. After trial and eror, I discovered my culprit was RSLinxNG.exe. Pull up task manager and click over to Processes tab and find RSLinxNG.exe and end the process. COM1 is now free.

I think RSLinxNG.exe is used for RSLinx Enterprise as I don't see it come up until I launched RSView Studio.

This isn't the fix you were looking for but, it's another thing people can look for when their COM1 is locked up.

Ken Roach · May 30th, 2008, 06:47 PM

I'm not aware of something that specifically looks at the COMx port and tells you which service or process is using it.

What I do is use the SysInternals "Process Explorer" (now owned by Microsoft).

http://technet.microsoft.com/en-us/s.../bb896653.aspx

In Process Explorer, select "Find Handle or DLL" and search for the word "serial". This should show anything that is using your serial ports.

Even if the process doesn't have a name, it will have a Process ID number (PID). You can go into the Windows Task Manager (via Ctrl-Alt-Del) and select View -> Select Columns to enable viewing the Process ID numbers, which can lead you to the image name of the program that's using your serial port.

It's a long way around, but it lets you get under the hood of the Windows COMx interface and peek around.

panic mode · May 30th, 2008, 07:06 PM

what was the software that had last successful connection?
that is probably your culprit...

ActiveSync etc. is also to be watched. the last time i used it, this was not the most cooperative thing to stop or remove.

danw · May 30th, 2008, 10:24 PM

Ken,

Thanks for that great link and explanation of Process Explorer.
You get a star for that effort!

bbopn · May 30th, 2008, 10:46 PM

Ken... Thanks for some good tips.

Quote:

I'm not aware of something that specifically looks at the COMx port and tells you which service or process is using it.

I wonder how hard it would be to come up with something like this. The only problem is the Serial Ports are almost like the dinosaur

Quote:

In Process Explorer, select "Find Handle or DLL" and search for the word "serial". This should show anything that is using your serial ports.

I loaded up Process Explorer, but I didn't get a hit on "serial" during the search. I then searhed "COM" and had a bunch of hits for COM3. Things that make me go hmmmmm.

I guess for now, I'll leave it defined as COM2 and keep trying to dive a little deeper as time permits.

Thanks again to everyone that answered.

==Bobby

pouch · May 31st, 2008, 04:32 AM

Try the following link, this will take you to other Microsoft utilities one of which is a Port monitoring utility.

http://technet.microsoft.com/en-us/s...84cb9e2f5.aspx

Regards

Paul.

OZEE · May 31st, 2008, 05:39 AM

What I usually do when I have problems with a COM port is to just go to Device Manager and delete the port, then reinstall it. It's a pain, but it works every time.

SNK · June 3rd, 2008, 02:09 PM

I too, have a Dell D620, that my Com1 port has been taken hostage now for quite sometime. Every re-boot, it captures the Com1 port again, and nothing else can access it.

I have tried process-explorer, numberous other applications, with no such luck. Nothing indicates COM1 useage.

The only way that I can get the COM1 back again is by uninstalling, and reinstalling in DeviceManager, and trust me, it is a royal pain in the ARSE, every time that you need it.

(I am using Win2K, SP4)

Other laptops in my group do not have this issue, but I have some more software installed.

I have uninstalled as much as possible, in an attempt to find out what is causing the problem.

The one thing that sticks in my head is that I tried a piece of software that someone posted here,

http://www.plctalk.net/qanda/showthr...ight=pocket+PC

I seem to remember my issues started after that....it could be a coincidence, but that is what I remember.

I am fed up changing my com ports before I connect to anything serially.

Does anyone have an update as to a fix?

I am going to try installing the above software on another laptop, and see if I can duplicate the issue...

Mickey · June 3rd, 2008, 02:14 PM

[quote=SNK

I am going to try installing the above software on another laptop, and see if I can duplicate the issue...[/QUOTE]

Make sure its the boss's laptop.

John M · June 3rd, 2008, 02:18 PM

I don't know if this will help but PortMon (available here)
http://www.download.com/Portmon/3000...-10630852.html
shows me what Process is using all of my ports that it is supposed to monitor.

SNK · June 3rd, 2008, 06:20 PM

John,tried that. Thanks for the info though.

That specific software is not that easy to figure out.
I tried some others that shows up all UDT,TCP/IP ports that are open, and indicates the process as well. But, it seems to be more ethernet related, and that it doesn't seem to be hardware serial ports. It shows about 12 services running on my corporate network, its IP addresses and such, but does not mention COM1 ports. (or any serial port that I can identify)

As I said, I have installed about 10 pieces of software today with no luck.

I am really thinking about reverting back to an older image that I knew worked. And then test in tiny increments.

rmceachran · September 20th, 2011, 06:31 PM

Hopefully I can get this thread going again because I am about to put my computer through a wall:

I have tried just about everything mentioned in this thread and more . It definitly seems like my com port is being taking over by something.

Strangely enough I keep thinking it is something to do with Rslinx Classis / Rslinx Enterprise

I have most of the latest and greatest software being:>

RsLinx Classic Professional 2.58.00.15
Factory Talk View Studio 6.0 (with no DF1 driver configured under Factory Talk view )

The cable I am using is 1761-cbl-pm02, serc

and I can not connect using my Rs-232 DF1 Device

I have changed com ports in BIOS I have closed RslinxNG processes.

I have used portmon and didnt quite understand the info I was seeing except for saying communication failed.

Here is a sample of what portmon displayed.
Rate: 1200

StopBits:1 Parity: EVEN Wordlength:8
EOF:0 ERR:0 BRK:0 EVT:0 XON:11 XOFF:13
Shake:1 Replace:40 Xonlimit:2048 Xofflimit:512

RI:-1 RM:0 RC:0 WM:0 WC:0
Purge:TXABORT RX ABORT TXCLEAR RXCLEAR
Mask: RXCHAR BRK ERR

Length 4
Mask: RXCHAR BRLK ERR

If any one has ANY insight at all I am willing to try anything.

OkiePC · September 20th, 2011, 08:43 PM

Quote:

Originally Posted by rmceachran

Hopefully I can get this thread going again because I am about to put my computer through a wall:

I have tried just about everything mentioned in this thread and more . It definitly seems like my com port is being taking over by something.

Strangely enough I keep thinking it is something to do with Rslinx Classis / Rslinx Enterprise

I have most of the latest and greatest software being:>

RsLinx Classic Professional 2.58.00.15
Factory Talk View Studio 6.0 (with no DF1 driver configured under Factory Talk view )

The cable I am using is 1761-cbl-pm02, serc

and I can not connect using my Rs-232 DF1 Device

I have changed com ports in BIOS I have closed RslinxNG processes.

I have used portmon and didnt quite understand the info I was seeing except for saying communication failed.

Here is a sample of what portmon displayed.
Rate: 1200

StopBits:1 Parity: EVEN Wordlength:8
EOF:0 ERR:0 BRK:0 EVT:0 XON:11 XOFF:13
Shake:1 Replace:40 Xonlimit:2048 Xofflimit:512

RI:-1 RM:0 RC:0 WM:0 WC:0
Purge:TXABORT RX ABORT TXCLEAR RXCLEAR
Mask: RXCHAR BRK ERR

Length 4
Mask: RXCHAR BRLK ERR

If any one has ANY insight at all I am willing to try anything.

I believe that RSLinx Enterprise and RSLinx Classic can get into a battle over the serial port and everybody loses.

I don't have the latest technotes with "RSLinx Enterprise" and what to look for but I think a search based on that quoted text here and at ab.com should help

May 30th, 2008, 04:52 PM	#1
bbopn Lifetime Supporting Member Join Date: Jun 2003 Location: Tulsa, OK Posts: 37	Determining what is using the Serial Port About a month ago I was at a customer's jobsite and used Mdbus Modbus simulator while troubleshooting some DCS problems. I connected to the ProSoft Modbus Card via my Latitude D830 serial port (COM1) without issue and even connected to a Woodward Governer and 489 Multilin... all via the COM1 port. Earlier this week a co-worker wanted to do some Modbus simulation and asked if I would set up my computer to be a Slave and he would set his up to be the Master. When I tried turning the Mdbus simulator "On", it gave me a message that said it couldn't open the comm port. I then ran RSLinx opened my drivers and attempted to start the DF1 driver. It gave me a message similar to what Mdbus and the DF1 status had a "Port Conflict" on it. I realized then that something had grabbed control of my COM1 port and attempted several things like turning services OFF, uninstalling some programs I had loaded up since the last time the COM1 port worked. This did not yield anything. I then went into my BIOS and changed the comm port to COM2 and the on board comm port is now working. My question is this.... Is there any program that can help you determine what is taking control of the serial comm port? I did a cursory Google search and didn't come up with much. AB's knowledge base wasn't much help either. It said to close the application that was using the comm port.... which I would do IF I knew what application was using it. Any direction on this would be greatly appreciated. Even though I have my serial port back by reassigning it to COM2, I feel like this is a cheesy fix and would like to determine what is taking control of the comm port. Thanks, Bobby __________________ Times and technology have changed so much. i remember my first laptop... an etch-a-sketch...

May 30th, 2008, 06:47 PM	#4
Ken Roach Lifetime Supporting Member + Moderator Join Date: Apr 2002 Location: Seattle, WA Posts: 8,712	I'm not aware of something that specifically looks at the COMx port and tells you which service or process is using it. What I do is use the SysInternals "Process Explorer" (now owned by Microsoft). http://technet.microsoft.com/en-us/s.../bb896653.aspx In Process Explorer, select "Find Handle or DLL" and search for the word "serial". This should show anything that is using your serial ports. Even if the process doesn't have a name, it will have a Process ID number (PID). You can go into the Windows Task Manager (via Ctrl-Alt-Del) and select View -> Select Columns to enable viewing the Process ID numbers, which can lead you to the image name of the program that's using your serial port. It's a long way around, but it lets you get under the hood of the Windows COMx interface and peek around. __________________ "Intelligence is the capacity to know what we are doing and instinct is just instinct. The results are about the same."

May 30th, 2008, 07:06 PM	#5
panic mode Member Join Date: May 2003 Location: Toronto, Canada Posts: 1,961	what was the software that had last successful connection? that is probably your culprit... ActiveSync etc. is also to be watched. the last time i used it, this was not the most cooperative thing to stop or remove. Last edited by panic mode; May 30th, 2008 at 07:08 PM.

May 30th, 2008, 10:24 PM	#6
danw Member Join Date: Oct 2004 Location: midwest, USA Posts: 1,703	Ken, Thanks for that great link and explanation of Process Explorer. You get a star for that effort! Last edited by danw; May 30th, 2008 at 10:26 PM.

May 31st, 2008, 04:32 AM	#8
pouch Member Join Date: Apr 2006 Location: Chester Posts: 44	Port Monitoring. Try the following link, this will take you to other Microsoft utilities one of which is a Port monitoring utility. http://technet.microsoft.com/en-us/s...84cb9e2f5.aspx Regards Paul.



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May 30th, 2008, 05:55 PM	#2
danw Member Join Date: Oct 2004 Location: midwest, USA Posts: 1,703	I have searched in vain for the utility that would report what has taken possession of the COM port without success. If you discover such a thing, would you be sure to tell us? The only thing I can think of is to take a screen shot of task manager (for a record of the list or running apps), then do the laborious task of figuring out which running app could grab the serial port. If you're like me, you won't know what most of them do, so it'll be the Google-the-executable-file-name-effort to see what comes up. Dan

May 30th, 2008, 06:26 PM	#3
gmferg Lifetime Supporting Member + Moderator Join Date: Feb 2008 Location: Modesto, CA Posts: 303	I've had a similar thing happen to me on occassion. After trial and eror, I discovered my culprit was RSLinxNG.exe. Pull up task manager and click over to Processes tab and find RSLinxNG.exe and end the process. COM1 is now free. I think RSLinxNG.exe is used for RSLinx Enterprise as I don't see it come up until I launched RSView Studio. This isn't the fix you were looking for but, it's another thing people can look for when their COM1 is locked up.

May 31st, 2008, 05:39 AM	#9
OZEE Member Join Date: Mar 2006 Location: Kansas Posts: 1,670	What I usually do when I have problems with a COM port is to just go to Device Manager and delete the port, then reinstall it. It's a pain, but it works every time.

June 3rd, 2008, 02:09 PM	#10
SNK Member Join Date: May 2004 Location: Toronto, Ontario Posts: 877	I am struggling with the same problem I too, have a Dell D620, that my Com1 port has been taken hostage now for quite sometime. Every re-boot, it captures the Com1 port again, and nothing else can access it. I have tried process-explorer, numberous other applications, with no such luck. Nothing indicates COM1 useage. The only way that I can get the COM1 back again is by uninstalling, and reinstalling in DeviceManager, and trust me, it is a royal pain in the ARSE, every time that you need it. (I am using Win2K, SP4) Other laptops in my group do not have this issue, but I have some more software installed. I have uninstalled as much as possible, in an attempt to find out what is causing the problem. The one thing that sticks in my head is that I tried a piece of software that someone posted here, http://www.plctalk.net/qanda/showthr...ight=pocket+PC I seem to remember my issues started after that....it could be a coincidence, but that is what I remember. I am fed up changing my com ports before I connect to anything serially. Does anyone have an update as to a fix? I am going to try installing the above software on another laptop, and see if I can duplicate the issue...

June 3rd, 2008, 02:14 PM	#11
Mickey Lifetime Supporting Member Join Date: May 2003 Location: Palmdale,Ca Posts: 7,585	[quote=SNK I am going to try installing the above software on another laptop, and see if I can duplicate the issue...[/QUOTE] Make sure its the boss's laptop. __________________ Mickey If you want happiness for an hour-take a nap. If you want happiness for a day-go fishing. If you want happiness for a month-getmarried. If you want happiness for a year-inherit a fortune. If you want happiness for a lifetime-help someone else. ----- Chinese Proverb

June 3rd, 2008, 02:18 PM	#12
John M Member Join Date: Mar 2004 Posts: 80	I don't know if this will help but PortMon (available here) http://www.download.com/Portmon/3000...-10630852.html shows me what Process is using all of my ports that it is supposed to monitor.

June 3rd, 2008, 06:20 PM	#13
SNK Member Join Date: May 2004 Location: Toronto, Ontario Posts: 877	John,tried that. Thanks for the info though. That specific software is not that easy to figure out. I tried some others that shows up all UDT,TCP/IP ports that are open, and indicates the process as well. But, it seems to be more ethernet related, and that it doesn't seem to be hardware serial ports. It shows about 12 services running on my corporate network, its IP addresses and such, but does not mention COM1 ports. (or any serial port that I can identify) As I said, I have installed about 10 pieces of software today with no luck. I am really thinking about reverting back to an older image that I knew worked. And then test in tiny increments. Last edited by SNK; June 3rd, 2008 at 06:23 PM.

September 20th, 2011, 06:31 PM	#14
rmceachran Member Join Date: Feb 2011 Location: Brantford Posts: 4	Hopefully I can get this thread going again because I am about to put my computer through a wall: I have tried just about everything mentioned in this thread and more . It definitly seems like my com port is being taking over by something. Strangely enough I keep thinking it is something to do with Rslinx Classis / Rslinx Enterprise I have most of the latest and greatest software being:> RsLinx Classic Professional 2.58.00.15 Factory Talk View Studio 6.0 (with no DF1 driver configured under Factory Talk view ) The cable I am using is 1761-cbl-pm02, serc and I can not connect using my Rs-232 DF1 Device I have changed com ports in BIOS I have closed RslinxNG processes. I have used portmon and didnt quite understand the info I was seeing except for saying communication failed. Here is a sample of what portmon displayed. Rate: 1200 StopBits:1 Parity: EVEN Wordlength:8 EOF:0 ERR:0 BRK:0 EVT:0 XON:11 XOFF:13 Shake:1 Replace:40 Xonlimit:2048 Xofflimit:512 RI:-1 RM:0 RC:0 WM:0 WC:0 Purge:TXABORT RX ABORT TXCLEAR RXCLEAR Mask: RXCHAR BRK ERR Length 4 Mask: RXCHAR BRLK ERR If any one has ANY insight at all I am willing to try anything.

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