clear com port assignments

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How to Delete COM Port In Use?

Every time you plug in a COM or USB device to your computer, Windows creates a virtual COM port and assigns it to a device. A new COM port with a unique number from 1 to 255 is created for each connected device (COM1, COM2, COM3, etc). Even if you unplug (turn off) the external device from your computer, the COM port number assigned to it remains reserved (Windows shows it as “in use”). This may exhaust free virtual COM ports on the computer.

In this article, we will show you how to delete COM ports in use or change assigned COM port numbers on Windows.

Note . Although modern computers almost never have physical serial COM ports (such as RS-232), virtual COM ports are still commonly used in Windows for emulated ports created by USB (USB-to-UART, USB-to-COM, USB modem, card/RFID reader) and Bluetooth adapters.

How to Manually Change COM Port in Windows

Some legacy apps can only address COM port numbers 1 to 9. If your device is assigned a high COM port number, you can change it manually using Device Manager.

For example, Windows has reserved the COM24 port for your device, but you need the COM9 port number.

Expand Ports ;

A warning may appear stating that the selected COM port number is already in use. You can ignore this warning by selecting “Yes” and this should not cause any issues.

These steps won’t help if Windows says the COM Port you need is already in use. In this case, manually delete the used COM port and reassign it to a new device.

Delete COM Ports in Use on Windows

You can clear the COM port reservation for a device that is not connected to the computer.

Expand the Ports (COM & LPT) section. The COM port number reserved for each device is shown. Disconnected devices have grayed-out icons;

DO NOT check the option “Delete the driver software for this device”;
Repeat these steps until all grayed-out COM ports are removed;
You can now assign a free COM port number to the device you need.

How to Check Which Program Uses the Serial (COM) Port

In some cases, to free up a serial port (COM port), you will need to find out which application is using the port.

You can use the Process Explorer tool to check which particular Windows process is using the COM port.

Open the Device Manager , expand Ports (COM & LPT) , right-click on the COM port you want to check, and select Properties ;
Go to the Details tab, select Service from the Property dropdown list ;

Download the Sysinternals Process Explorer utility from the Microsoft website;

In the Handle or DLL substring search box, enter the name of the service that uses your COM port. In our example, this is serial . Click Search;

You have unlocked the COM port and can assign it to your device.

Clear COM Ports Using the COM Name Arbiter Tool

Also, you can easily delete COM ports using the free third-party tool called COM Name Arbiter .

Download the COM Name Arbiter Tool from the official website and run the executable file with Administrator privileges.

Tool shows the list of COM ports with checkmark next to the currently busy ports of connected devices. Press the Remove non-present devices to clear all assigned COM port number reservations.

You can also clear the COM port manually, by unchecking a specific device from the list.

Another handy tool for viewing COM port configuration is COM Port Info . This tool allows you:

View assigned COM port numbers;
Safely remove hardware;
Change and swap COM port numbers;
Reset USB Ports.

Removing Unused COM Ports via CMD

You can use the built-in PnPUtil tools to list and remove assigned COM ports from the command prompt.

List COM port devices:

In this example, you can see that the COM3 port is occupied by a MediaTek USB Port device. This device is currently not connected (Status: Disconnected).

Copy the Instance ID and remove this COM device with the command:

Reset COM Ports Using the Registry Editor

Now let us talk about the most difficult low-level method of deleting used COM ports in Window.

Windows stores COM ports assignments in the registry value of the ComDB parameter under reg key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\COM Name Arbiter. You can make direct changes to the registry to reset COM port reservations.

Caution . It is recommended that you create a system restore point before making these registry changes.

Disconnect any peripheral devices from the computer;

Go to the reg key Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\COM Name Arbiter ;

Restart your computer. When it boots back, connect all the COM devices in the proper order.

Now you know how to delete COM ports and reassign them to a different device.

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Windows OS Hub / Windows 10 / How to Clean Up or Reset COM Port Numbers in Windows

How to Clean Up or Reset COM Port Numbers in Windows

A number of legacy applications are able to address only two-digit COM port numbers, and won’t work with COM100 and higher. In the worst cases, these programs work only with COM1-COM9 ports. What if a device has got a higher COM port number? Is it possible to reset the numbering for reserved COM ports and delete assigned ports?

How to Change a COM Port Number for a Device in Windows?

Find out which process is using a serial com port in windows, resetting com port numbers in windows registry.

In Windows, you can manually change the COM port number assigned to a device. Suppose the necessary COM port is already busy, and you want to try to free it.

Open the Device Manager by running the devmgmt.msc command;

Then expand Ports (COM & LPT) and find your device in the list;
Go to the Port Settings tab and click the Advanced button;
The current COM port number assigned to the device can be found in the COM Port Number field;

But more often you cannot change the assigned COM port number to another one in the hardware properties, since all the “lower” COM ports are already in use.In this case, you need to try to remove the COM port reservation

Expand the Ports (COM & LPT) branch, find which COM port number you need is assigned to (a pale icon means that this COM port is assigned, but this device is not currently connected);

Get-WMIObject Win32_SerialPort | Select-Object Name,DeviceID,Description You can get the COM port number for a specific device by its name, for example:

Get-WMIObject Win32_SerialPort | Where-Object { $_.Name -like "*Arduino*"}|select name, deviceid or Get-WMIObject Win32_SerialPort | Where-Object { $_.Name -like "*GPS*"}|select name, deviceid

You won’t be able to release the COM port of a device that is used by Windows or a running program (process). First, you need to stop the process that is currently using the COM port. You can use the Process Explorer tool (by Sysinternals) to find out the name of the process using a particular COM port number ( https://docs.microsoft.com/en-gb/sysinternals/downloads/process-explorer ).

First, you need to display the name of the service that uses the COM port. Run the PowerShell command:

get-pnpdevice -class Ports -ea 0| Select Name, PNPDeviceID, Status, Service

The service name of the specific COM port is shown in the Service column. For example, for COM2 it is Serial . Now you need to run Process Explorer as an administrator and select Find -> Find Handle or DLL from the menu. In the Handle or DLL substring line, enter the Service value obtained earlier. In our example, this is Serial .

Process Explorer should show the process name that is currently using your COM port. To release the COM port, kill the process or program.

process explorer - getting process name is using serial com port number

Information about the COM ports in use is stored in CommDB registry parameter under the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\COM Name Arbiter reg key.

Unplug all external devices and restart your computer;
After the reboot, connect the devices in the necessary order, reinstall USB-to-serial converters, etc. All detected COM port devices will be automatically detected by the system and assigned sequential COM port numbers.

You can also use the following free tools to clean up reserved COM ports:

com name arbiter reset tool to reset com port number assignment

Device Cleanup Tool – the utility is used to search the registry for previously connected devices (under the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum ), remove unused devices, and clear COM port reservations.

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Hi dear When I open Device Manager there is no branch of (COM & LPT) to expand. How can I Add or Find it?

thank you so much

thanks you so much , life saving post 🙂 , i mostly work with iot devices and sometime com ports get busy and am getting com port busy returns in code so this saved my life in flushing com port

Thank you for the post, very helpful

WHAT IS COM PORT?

How to reset com ports, how to disable adding new com port numbers, how to clear or reset com ports.

HOW TO CLEAR OR RESET COM PORTS?-Uncategorized

COM port (Communication port) is the name for the port serial interface that can be found in a common computer(IBM compatible). Sometimes computers come with one or two physical COM ports (RS-232), while today’s models don’t have them ususally. However, the COM port does not necessarily refer to physical ports, but also virtual. Such ports are created when using USB-to-UART adapter , most notably used by FTDI and Croduino. Here are a few examples of such devices: USB modems, cell phones, RFID readers , card readers, and so on.

Every time Windows register such a device with a new ID, it gives that device a new COM port (COM2, COM3, COM4, etc.). Even when you turn off the device, the COM port that is assigned to the device remains reserved for it. That is, each time you reconnect they will be assigned to the same COM port. Generally it’s great. The problem can occur if some software that comes into your device is set so that it can access only, say, the first five COM ports. However, this tutorial will describe how to “clean” COM ports that are in use, and how to disable numbering of new ports.

1. Click Start – write regedit then click Enter. 2. Navigate through folders: HKEY_LOCAL_MACHINE\SYSTEM\CurrentConstrolSet\Control\COM Name Arbiter

Once you confirm the changes by clicking on OK , our ports are reset. We can also check:

1. Click Start – write devmgmt.msc or simply Device manager , then click Enter. 2. From the middle pane, expand Ports (COM & LPT) , right-click on any of the available ports and Properties 3. Choose Port Settings and click Advanced 4. Click on the drop down menu COM Port Number , and we see that all COM ports available.

Check those ports after Windows assignes them a COM port, there should be written “ in-use “.

As the title says, follow the instructions to disable the Windows computer from getting the new COM port number each time a new USB-to-UART device is connected.

1. Click Start – write regedit then click Enter. 2. Navigate through folders: HKEY_LOCAL_MACHINE\SYSTEM\CurrentConstrolSet\Control\usbflags

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How can I remove all COM ports from the command line on Windows 7?

We have a computer that's used to test some devices. Every once in a while, testers need to go in and remove the assigned COM ports so they free up and start back at 1. Lately, it's been assigning them the same COM port to a couple of devices (around 8 are connected at the same time) and also, they need to change the test code to match whatever number was assigned by the OS.

Duplicate numbers was the reported problem, but I see the 'having to check the COM ports and updating the code' multiple times a day as a problem too.

In Device Manager , if I turn on to show hidden devices, I see hundreds of them!

You can tell by the size of the scrollbar the list is pretty big. I can click at each one and uninstall, but that's insane going 1 by 1 which is why I ask for a command-line alternative, so I can write a script that they can double click when they need to reset the ports.

Of course, if there's some software out there that will allow for this to happen then that's good too.

command-line

2 Answers 2

Remove active USB ports:

Remove active LPT and COM ports:

Query all COM and LPT ports:

Query active USB ports:

Query all USB ports - different results:

Enum all devices:

Part at WDK, Windows Driver Kit Version 7.1.0 .

The old version, 2003-01-29, does not work on Windows 7 (not del device). devcon old version 2003-01-29

Source code for DevCon

Alternative 1 - PnPUtil

Alternative 2 - registry key, search USB device at subkey

Not del all!

If ports enumerate devcon FindAll =Ports - delete this registry key:|

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\ACPI

If ports enumerate devcon status @usb\* - delete this registry key:|

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\USB

Thx geermc4! I tested devcon. On Windows Driver Kit Version it works correctly with Windows 7.

The hardware profile can be set up only for Windows XP. We will not be able to setup on Windows 7. It is by design ... backup HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum ...

that place you suggested in the registry does look like the place, but devcon seems more straight forward, I do see a long list of devices with devcon, but when i try the remove command i get 'Remove Failed' on all – geermc4 Commented Feb 7, 2013 at 0:29
@geermc4 port enumerate devcon FindAll =Ports or devcon status @usb\* ? – STTR Commented Feb 7, 2013 at 0:32
2 those did work, just remove failed, I was trying with the old version link since it is a single smaller file to download, but now trying with the new version and that is working yay! – geermc4 Commented Feb 7, 2013 at 0:43
1 @geermc4 Thx at good comment! Good Luck! – STTR Commented Feb 7, 2013 at 1:33

I also need to test hundreds of units. However I tried to use command line " devcon /r remove @usb*" and devcon /r remove =ports", which did not work. I also download WDK (donot know how to use it). I felt confused after reading the conversation. @geermc4 and @STTR, would you explain again how you did it?

This does not really answer the author's question, due to the clarification request, answer should only be used to answer a question. – Ramhound Commented Feb 8, 2017 at 21:38
This is not an answer to the original question. If you have a new question please ask your own question (referencing this one for context if it helps). – DavidPostill ♦ Commented Feb 9, 2017 at 10:41

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Manage COM Port Assignment in Windows 10

This question was asked by Praxair and answered by Brendan3385 but the solution given was product specific and did not solve the issue by modifying Windows 10. That is the type of solution I need.

REF: Windows 10 assign specific COM port to device

I am using digital calipers, Tesa micro heights, and other peripheral measurement devices, running through Midwest flexports with 25 pin serial to USB cables. These run to Dell Optiplex 3070 thin clients into an application called WINSPC.

WINSPC requires specifying the COM port in the application. Windows 10 self manages the assignment of COM ports. It frequently changes this assignment when rebooted or the serial to USB cable is unplugged. When it assigns a different COM port the measurement devices lose the ability to transmit data. I know I can change this manually in device manager every time as an admin but my users can not. I need to stop it from happening.

My ideas are possibly a registry edit, a locally placed startup script, or even a script attached to the profile in active directory.

I will need to frequently solve these types of issues throughout my career so if possible I would rather be taught to fish rather than find one in my desk drawer…

Thanks Everyone!

@lauren7060 @marcmaehner7836 @brendanshreve7169 @pblais

I use a USB Serial Port to access CLI on a Cisco ASA. But, if you open up Device Manager, right-click on device, port settings, advanced. There’s a number of settings, including the COM Port assignment. I quickly tested that assigning to 9, then moving around to different USB slots came up with same COM Port.

As far as Regedit goes, you might check \HKLM\HARDWARE\DEVICEMAP\ - in my case, \SERIALCOMM for the specific setting of COM9 as the example.

Is your thin client connecting to a VM or a RDS Session Host?

This article may be of some assistance. If you can find somewhere to view/update the serial numbers from each device, it should in theory always keep that COM port.

I’m going to look into this on some of our machines here to see if I can replicate this issue.

According to experience before, the Windows assign the COM port according VID, PID and serial number. So with the same device plug in, it should always get same COM port assignment. However, two devices with same VID, PID and serial number might be treated as same device. When you plug in them in sequence, Windows can assign different COM port for them. However, after rebooting the Windows with the two USB devices attached, the COM port assignment should be decided by Windows for the two USB devices with same VID, PID and serial number.

It is connecting to an RDS session.

Der Geist , Thank you, I tried doing what you did by selecting a COM port ( #9 ) that was unlikely to be used by Windows 10. Rather than fight Windows 10 over the COM3 or COM4 slots I sort of harmonized with it by allowing it to have the ability to allocate (manage) the first few (usable) ports as, or if, things get plugged/unplugged and I assigned it to something that should never be used like COM9. After several tests of unplugging rebooting etc… it continues to assign it to COM9

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Finding & Removing Hidden COM Ports

Finding & Removing Hidden COM ports for Non-connected Devices in Windows XP (this procedure also works for Windows 7 & 10)

Thanks to Jack, KF6T, Rick, N6XI, Ward, N0AX, and Steve, N2IC, as sources for the information on this page. Since ham radio operators use COM ports to communicate with various devices in their stations, there may be a time when you need to clean out old and unused COM port assignments which were created, but not deleted, by Windows XP. This may be useful if you have problems installing new COM port devices such as USB Serial Adapters or legacy serial ports. Or when installing COM devices, Windows assigns higher COM port numbers such as COM18, etc. In most cases, you can over-ride the port number that Windows assigns by going to the Properties of the device in Device Manager , then to the Port Settings tab and click on the Advanced button. Or by using one of the two procedures below, you can eliminate old and unused COM ports to free up resources for devices you already have installed and wish to move to a lower port number or for devices you wish to install in the future.

Two procedures are shown below. The first one is a permanent solution where all hidden devices (including COM ports) will be shown each time Show Hidden Devices is enabled in the View menu of Device Manager . The second procedure is for showing all hidden devices on a temporary basis and includes how to delete hidden COM ports to free up resources. I’ve performed both procedures on both my shack computers where old assignments of COM ports remained for devices I no longer use. I am now set for the permanent solution. Both procedures are outlined by Microsoft at http://support.microsoft.com/kb/315539 .

Procedure for Permanent Fix to Finding Hidden Devices in Device Manager

1. Right click on My Computer then go to Properties .

9. To delete a particular port, click to highlight it and hit the Delete key on your keyboard. In the Confirm Device Removal dialog box, click OK .

10. After you have deleted the unused and hidden COM ports, the list will show only those COM ports you use or may use in the future (during the procedure, you may have to scroll back down Device Manager to get back to the Ports section.) Notice I kept the unused COM6 for my Keyspan USB Serial Adapter even though it is not connected and not being used at the moment. When I connect my Keyspan adapter, it always comes up COM6 now which is what I want.

Procedure for Temporarily Finding Hidden Devices in Device Manager

1. COM ports assignments can be viewed from the Windows Device Manager . There are a couple of ways to get to the Device Manager . The easiest way, if you have a My Computer icon on your desktop, is to right-click My Computer and go to Properties . The other way is to go to theStart | Control Panel | System | Hardware | Device Manager.

2. When the Systems Properties dialog window opens, click on the Hardware tab.

3. On the Hardware tab, click on the Device Manager button.

4. In Device Manager , click the + sign next to Ports (COM & LPT) to reveal what ports are currently in use.

5. You will notice if you go to the View menu in Device Manager and click on Show hidden devices , that nothing changes in your Ports list.

6. To view actual hidden COM ports, close Device Manager . Go to Start > Run .

7. When the Run dialog box opens, type cmd.exe and hit enter or click OK .

8. When the cmd window opens, type set devmgr_show_nonpresent_devices=1 then hit Enter .

9. Then open Device Manager from the cmd window by typing start devmgmt.msc and hit Enter . (Note, if Device Manager does not open when you start devmgmt.msc , then type cd\windows\system32 and hit Enter, then type start devmgmt.msc and hit Enter .)

10. When Device Manager opens, go to the view menu and click Show hidden devices (same as Step #5 above). Scroll down to the Ports section and you will be able to see all the hidden COM ports. In this particular example, there are seven hidden COM ports showing on my main shack desktop computer. Of these seven, six are for devices I no longer use. I occasionally use the Keyspan port showing as (COM6) so decided to keep it.

11. To delete a particular port, click to highlight it and hit the Delete key on your keyboard. In the Confirm Device Removal dialog box, click OK .

12. After you have deleted the unused and hidden COM ports, the list will show only those COM ports you use or may use in the future (during the procedure, you may have to scroll back down Device Manager to get back to the Ports section.) Notice I kept the unused COM6 for my Keyspan USB Serial Adapter even though it is not connected and not being used at the moment. When I connect my Keyspan adapter, it always comes up COM6 now which is what I want.

13. When finished, close Device Manager . To close the cmd window, type EXIT and hit Enter . The box will close.

Note that any time you close the cmd window, you lose the context that permits Device Manager to display and manage COM ports for non-connected devices. To check again, you have to perform the procedure over or else use the permanent fix on the Microsoft webpage listed at the beginning of this page. On my laptop, I tried to delete unused Bluetooth COM ports that were assigned the same port numbers as my USB serial adapter. After a reboot, these Bluetooth COM ports returned to the hidden list even though they were not being used. The only problem it poses is when I disconnect my USB serial adapter and then reconnect it. Windows may assign different COM ports numbers than what I previously used and have been assigned in my software. There are 64 COM ports showing on my XP laptop because of Bluetooth. So far, this hasn’t caused any conflicts that I am aware of.

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how to assign static COM port number to a device

I have an issue with one device ( Pax Technology Terminal ) connected to Win 10 ( NCR Point of Sale ). after unplugging the device and connecting it the COM port number changes and every time we have to change the port number back to the correct port number for this device to work.

Is there way I set this device to only get a certain COM port number every time they unplug and connect it back ?? something like setting defaults for each device type

Windows 10 A Microsoft operating system that runs on personal computers and tablets. 11,022 questions Sign in to follow

Dear all USB Users, (unsure that this is the right forum for my question...)

Is there a way to programmatically "Recover Unused and FIX COM Numbers" (NI - National Instrument Forum Question...)

It is hard to live with the Totally Random USB COM port Enumeration that Windows always apply... Is there a way to make this less Random, or even totally controlled and pre-visible?

I found that for each USB device the following apply (or at least should apply) Each device has:

VID = Vendor ID
PID = Product ID
PSN = Product Serial Number So with we have the possibility to make a COM-Port-Number Reservation/Binding Option for this USB device with Unique ID: VID&PID&PSN This would result in the possibility for having the desired Unique Fixed COMxx Port Number Reservation...

See my proposal in the attached TXT document... 269324-windows-usb-com-port-enumeration-problem.txt

The Simple Solution to this Problem could be just like **DHCP MAC-Address to IP-Address binding... Like VID&PID&PSN to COMxx Port Binding forever on this computer...

Thanks... The World and I would appreciate a COMMENT to this... And much better also an action to this problem...!

Thank you for reading ana all the best regards Ronn

I encountered similar issue. When the COM number is assignated and confirmed, Device Manager is closed automatically and the COM number remains unaffected.

Windows manages the COM port number assignments, and a device's COM port number may change after a reboot.

To manually change the COM port number of a device:

Open Windows Device Manager > right click the device > Properties
Under Port tab > Advanced
Change COM port number

Also, according to the experience before, the Windows assign the COM port according VID, PID and serial number. So with the same device plug in, it should always get same COM port assignment. But when two devices with same VID, PID and serial number might be treated as same device. When you plug in them in sequence, Windows can assign different COM port for them. However, after rebooting the Windows with the two USB devices attached, the COM port assignment should be decided by Windows for the two USB devices with same VID, PID and serial number.

-------------------------------------------------------------------------------------

If the Answer is helpful, please click " Accept Answer " and upvote it.

How can ANY two devices have the same serial numbers ??

GW Electrical and Computer Engineering Laboratories

Resetting Windows COM Ports

Here are instructions helps ECE 3520 students that are having issues with COM ports using the STK 500.

What is a COM port?

COM port (Communication port) is the name for the port serial interface that can be found in a common computer(IBM compatible). Sometimes computers come with one or two physical COM ports (RS-232), while today's models don't have them ususally. However, the COM port does not necessarily refer to physical ports, but also virtual. Such ports are created when using USB-to-UART adapter, most notably used by FTDI and Croduino. Here are a few examples of such devices: USB modems, cell phones, RFID readers, card readers, and so on.

Every time Windows register such a device with a new ID, it gives that device a new COM port (COM2, COM3, COM4, etc.). Even when you turn off the device, the COM port that is assigned to the device remains reserved for it. That is, each time you reconnect they will be assigned to the same COM port. Generally it's great. The problem can occur if some software that comes into your device is set so that it can access only, say, the first nine COM ports. However, this tutorial will describe how to "clean" COM ports that are in use, and how to disable numbering of new ports.

How reset COM Ports.

Use one of the two methods to reset the COM ports on your Windows computer.

Click start –> Run –> type regedit and click OK button.
Registry editor will open.
Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\COM Name Arbiter
In the right panel , you'll see a key ComDB right click to that key and click modify.
In value Data section select all and delete reset to Zero ‘0’.
Close Registry editor and then restart your computer. All COM ports are now Free. You might need to reinstall any USB to serial convertor.
Click go to Start, type devmgmt.msc in the Start Search box, and then press ENTER.
In Device Manager, double click Ports (COM & LPT) to expand this section.
Right click Communications Port (COM1) and then click Properties.
Click Port Settings tab and then click Advanced… button.
Pull down COM Port Number list, choose one of the com port in use and then click OK.
When a warning message occurs, please ignore it and click Yes directly.
Please repeat step 3 to 7 to choose another com port in use. Once the above steps are completed, please change the port back to original (COM1) setting.

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How to assign a COM port number?

We are using a USB-to-Serial converter. Windows assigns a COM port number to the serial device. For testing purposes, we need to control the COM port number assigned by Windows. For example, we would like to tell Windows to assign COM 255 to a device rather than have Windows decide what the number is. Is there any way to do this?

serial-port

1 Assign it programmatically ? if so, what language ? otherwise, you can do it from Device Manager in Windows. – Nasreddine Commented Nov 17, 2011 at 15:40
1 This is the most odd test requirement I've seen in awhile... – Brad Commented Nov 17, 2011 at 15:41
1 It is up to the driver, not Windows. Finding a converter with a driver that lets you do this is going to be hard shopping. The odds that your user will have one are even smaller. – Hans Passant Commented Nov 17, 2011 at 15:48

3 Answers 3

I do not have to do this programmatically, so Nacereddine is right. My Computer -> Manage -> Device Manager -> Ports -> Communications Port -> Port Settings -> Advanced -> COM Port Number

1 My answer basically said the same thing, but without as much detail because the details depend on the driver. If you are going to accept your own answer which says almost the same thing you should specify the device make/model so that people understand that your answer might be specific to that make/model. – Shane Wealti Commented Nov 23, 2011 at 0:53

This normally depends on the driver. Some drivers allow you to edit the COM port number assigned by going into the device properties in device manager and using one of the properties pages to specify the COM port number. If the model you are currently using doesn't support this I suggest finding a model that does.

No, but if you know what device id it reports to the OS then its possible that you could find it programmatically in the device manager.

Here's a link to a code project that may give you some ideas.

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HOW TO: Remove Unused COM Ports for Re-assignment with Windows RealPort

This guide shows instructions on how to remove and change COM Port Assignments in Windows 7. Because the process requires you to enter the Device Manager, caution is advised .

Show all Com Port Assignments

Open a Command Prompt window, right click and select Run as administrator :

Type the following lines:

In Device Manager: click View , then Show Hidden Devices .

Expand the section labeled Ports (COM & LPT) to view all COM Ports that have ever been installed on this computer. COM Ports that have been assigned but are not currently connected will have a light-grey icon .

To remove an old COM Port

Right-click on the COM Port in question and chose Uninstall.

To change COM Port assignments

Expand the Multi-port serial adapters entry, right-click on the Digi device you want to change and chose Properties .
In the Properties window, click the Advanced tab, followed by Properties .
In the Advanced Properties window, click the desired port number on the left, then Serial .
Chose an unused COM Port from the drop-down list and click Apply .

Service Name and Transport Protocol Port Number Registry

COMMENTS

How to Delete Or Clear COM Ports In Use
Some legacy apps can only address COM port numbers 1 to 9. If your device is assigned a high COM port number, you can change it manually using Device Manager. For example, Windows has reserved the COM24 port for your device, but you need the COM9 port number. Press Win + R and run devmgmt.msc command; Expand Ports;
How to Clean Up or Reset COM Port Numbers in Windows
Select View->Show Hidden Devices in the menu; Then expand Ports (COM & LPT) and find your device in the list; Go to the Port Settings tab and click the Advanced button; The current COM port number assigned to the device can be found in the COM Port Number field; To change it, open the drop-down list and select the COM port number you want to set.
How to Clear or Reset Com Ports
Click Start - write devmgmt.msc or simply Device manager, then click Enter. 2. From the middle pane, expand Ports (COM & LPT), right-click on any of the available ports and Properties. 3. Choose Port Settings and click Advanced. 4. Click on the drop down menu COM Port Number, and we see that all COM ports available.
windows 7
1) Open Device Manager. 2) From the View menu, select 'Show Hidden Devices'. 3) Expand 'Ports (COM & LPT)' category from the list. 4) Right-click on all the devices and remove them (no need to tick to delete the driver) 5) From the Action menu, select 'Scan for New Devices'. 6) Viola!
How can I remove all COM ports from the command line on Windows 7?
Remove active LPT and COM ports: devcon /r remove =ports. Query all COM and LPT ports: devcon FindAll =Ports. Query active USB ports: devcon status @usb\*. Query all USB ports - different results: devcon findall @usb\*. devcon findall =USB.
Removing unused COM Ports from Windows
Show all Com Port Assignments. Open a Command Prompt window and type the following lines: set devmgr_show_nonpresent_devices=1. start devmgmt.msc. *This should automatically open the Device Manager for you. In Device Manager: click View, then Show Hidden Devices. Expand the section labeled Ports (COM & LPT) to view all COM Ports that have ever ...
How do I clear COM ports that are appearing as in use
Select and click Delete. The trick was to open the Command Prompt as administrator and start the Device Manager from the same command prompt. 1. Right-click "Command Prompt" in Accessories and choose "Run as Administrator". 2. Enter "set devmgr_show_nonpresent_devices=1″ - without the quotes obviously. 3.
Manage COM Port Assignment in Windows 10
WINSPC requires specifying the COM port in the application. Windows 10 self manages the assignment of COM ports. It frequently changes this assignment when rebooted or the serial to USB cable is unplugged. When it assigns a different COM port the measurement devices lose the ability to transmit data. I know I can change this manually in device ...
Change COM port via registry, command line or software?
Change the port number: In the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\COM Name Arbiter, you can find the ComDB which is a bit mask of COM ports already allocated. This value should be change based on your COM ports. Note, The first byte controls COM8~1, the second byte controls COM16~9, the third byte controls COM24~COM17 and so on.
How to Reset COM Port Numbers
1) Right-click on My Computer and select Properties. 2) Select the Hardware tab and open Device Manager. 3) Under 'Ports (COM & LPT)', right click on the COM port and select Properties. 4) Select the Port Settings tab and press the Advanced button. 5) At the bottom, select the desired COM Port Number from the drop down box and press OK.
Finding & Removing Hidden COM Ports
On the Hardware tab, click on the Device Manager button. 4. In Device Manager, click the + sign next to Ports (COM & LPT) to reveal what ports are currently in use. 5. You will notice if you go to the View menu in Device Manager and click on Show hidden devices, that nothing changes in your Ports list. 6.
How do I delete the unused COM ports in Windows 10?
Check if you are able to see any hidden devices in the Device Manager. Try these steps to create a new user account and check if it fixes the issue. Refer to the steps below to create a new User Account: Go to Settings. Choose Accounts and then select Other User Accounts towards the left. Select Add an Account.
COM port assignement changes after reboot
Windows manages the COM port number assignments, and a device's COM port number may change after a reboot. To manually change the COM port number of a device: 1. Open Windows Device Manager > right click the device > Properties . 2. Under Port tab > Advanced . 3. Change COM port number
how to assign static COM port number to a device
To manually change the COM port number of a device: Open Windows Device Manager > right click the device > Properties. Under Port tab > Advanced. Change COM port number. Also, according to the experience before, the Windows assign the COM port according VID, PID and serial number. So with the same device plug in, it should always get same COM ...
PDF How to Clear COM Port List
How to Clear COM Port List — When COM port number reaches 256 Log in your PC as administrator. From START menu, right click "Command ... usa Serial Port (COM182) usa Serial Port (COM183) usa Serial Port (COM184) Author: Engineering Created Date: 1/31/2019 3:32:54 PM ...
re-set COM ports
Click start -> Run -> type regedit and click OK button. This will open a Registry editor. Now right panel , you can see a key ComDB right click to that key and click modify. In value Data section select all and delete reset to Zero '0'. click OK. Close Registry editor and then restart your computer. all COM ports are now Free, you may ...
Resetting Windows COM Ports
In Device Manager, double click Ports (COM & LPT) to expand this section. Right click Communications Port (COM1) and then click Properties. Click Port Settings tab and then click Advanced… button. Pull down COM Port Number list, choose one of the com port in use and then click OK. When a warning message occurs, please ignore it and click Yes ...
COM-Port Manager
Or download the ComPortMan.msi file and right-click -> Install, which installs it silently to "C:\Program Files\ComPortMan" and registers + starts the ComPortMan service. Then enter your preferred configuration into the ComPortMan.INI (see below). There is a sample file included called ComPortMan_sample.INI.
Minimal Clear-Com Port Requirements
Minimal Clear-Com Port Requirements. The information on this page is owned by Clear-Com and constitutes Clear-Com's confidential and proprietary information, may be used solely for purposes related to the furtherance of Clear-Com' business and shall not be disclosed, distributed, copied or disseminated without Clear-Com's prior written ...
windows
My Computer -> Manage -> Device Manager -> Ports -> Communications Port -> Port Settings -> Advanced -> COM Port Number. answered Nov 17, 2011 at 20:45. Mr. T. 1,345 4 14 24. 1. My answer basically said the same thing, but without as much detail because the details depend on the driver.
How do I delete the unused COM ports in Windows 7?
Select Properties not Server Properties. Click on Ports Tab. Do you See COM listings? Select and click Delete. The trick was to open the Command Prompt as administrator and start the Device Manager from the same command prompt. 1. Right-click "Command Prompt" in Accessories and choose "Run as Administrator". 2.
Assignments
Assignments . Network transmission controls/transport settings are in this page (LQ only). This is where you will assign ports to Channels. All devices, with their associated ports appear in the left margin of this page. In the center are three tabs; chose from All, Channels and Directs. Channels (up to 24 in total per Link-Group) are shown on ...
HOW TO: Remove Unused COM Ports for Re-assignment with Windows RealPort
Expand the Multi-port serial adapters entry, right-click on the Digi device you want to change and chose Properties. In the Properties window, click the Advanced tab, followed by Properties. In the Advanced Properties window, click the desired port number on the left, then Serial. Chose an unused COM Port from the drop-down list and click Apply.
Service Name and Transport Protocol Port Number Registry
Port numbers are assigned in various ways, based on three ranges: System Ports (0-1023), User Ports (1024-49151), and the Dynamic and/or Private Ports ... * * * * ASSIGNMENT OF A PORT NUMBER DOES NOT IN ANY WAY IMPLY AN * * ENDORSEMENT OF AN APPLICATION OR PRODUCT, AND THE FACT THAT NETWORK * * TRAFFIC IS FLOWING TO OR FROM A REGISTERED PORT ...

How to Delete COM Port In Use?

How to Manually Change COM Port in Windows

Delete COM Ports in Use on Windows

How to Check Which Program Uses the Serial (COM) Port

Clear COM Ports Using the COM Name Arbiter Tool

Removing Unused COM Ports via CMD

Reset COM Ports Using the Registry Editor

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HOW TO: Remove Unused COM Ports for Re-assignment with Windows RealPort

Show all Com Port Assignments

To remove an old COM Port

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Service Name and Transport Protocol Port Number Registry

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