I met this problem today. When I debugged the serial port, I found that COM8 was used to convert usb to serial port, but there was only COM 1 to 4 in the serial port debugging assistant. I wanted to go to the COM port and found that COM 1 to 7 were all in use, but many solutions could not be found. Later, I found this article on the Internet and reprinted it. It's a bit bad not to indicate the reprint address, hehe.

A method to COMpletely solve the problem of com port being occupied

1. How to release the occupied COM port?

Com5 ~ Com 15 are all occupied due to repeated trial installation of different versions of Bluetooth drivers. After the driver is successfully installed, only COM 16 can be used, and synchronization software is not recognized. Who can explain? thank you

2. When using the USB-to-serial port device, because there is a problem with the previous device, it is found that all the COM ports used before are now in use, and the number of newly allocated COM ports of the device is counted down from before. For example, I tried COM7 before, but after I changed the new equipment, I came out of COM8 directly, and COM2-COM7 are all in use (COM 1 is reserved by the machine).

3. How to delete the used COM port in the computer?

My computer often uses Bluetooth, cell phone data cable and so on. Every time a new device is installed, windows will automatically assign a new virtual com port. Now I plug in a new device and use COM25. Looking at the device manager-port -com25 properties-port settings-advanced -com port number, I found that all devices from 3 to 24 are "in use". How can I delete the previous one?

Completely solve the above problems:

Open the registry HKEY _ local _ machine/system/current control settings/control /comname arbitration.

Delete ComDB and try again! (Note: This will rebuild all COM ports). If not, restart the computer!

Random note: The above methods have solved my problem. ...

In addition, you can also check whether the integrated modem occupies your serial port.

Open the phone/modem option in the control panel.

Is there a connection (such as COM 1) in the modem tab that occupies this serial port?

Solution:

If a connection occupies this serial port, directly delete this connection, restart the computer and solve the problem.

Or look at the detailed reasons:

1, start in safe mode, and test the serial port (COM 1) with the HyperTerminal in communication provided with the system.

At this point, the same error is reported, but the error information is more detailed, as follows:

* * * * * Error message * * * * * * *

Windows reported a TAPI error (80000048).

Please use the phone/modem option in the control panel.

Icon to confirm whether the modem is installed correctly.

**********************

Then I started the computer normally.

Open the phone/modem option in the control panel.

I found that a connection in the Modem tab occupied this serial port (COM 1).

So I immediately deleted this connection.

Then use "HyperTerminal" to test the serial port (COM 1), and there is no error.

It indicates that the communication with serial port (COM 1) is normal.

3. Connect the serial port device to the serial port (COM 1) and communicate with the device with related software. It's normal. The problem is solved.

The occupation of COM port when using bluetooth device

Due to the inexplicable registry of windows, many users find that after installing Bluetooth management software, the corresponding Bluetooth virtual port has actually become COM9, even COM 13 or above, which makes many applications unusable, such as mobile phone synchronization software and PDA synchronization software. Reinstalling Bluetooth management software many times will only make the situation worse. ..

The solution is as follows (please make sure to uninstall Bluetooth Manager and restart it before performing the following steps).

1. In Windows system, press Start >; Execute > enter cmd and press enter.

2. After the command character window appears, enter

set dev mgr _ SHOW _ non present _ DEVICES = 1

Press enter.

Development management

Press enter.

3. then click > view > show hidden devices.

You can now delete redundant ports. Please restart after deletion.

4. Reinstall the Bluetooth management software

5. If you want to permanently input this environment variable into XP, go to my computer >; After clicking, press the right mouse button > Properties > Advanced > Environment Variables.

In the system variable, press "New", fill in "devmgr _ show _ non-presented _ devices" in the variable name and "1" in the variable value.