How do I get the friendly name of a COM port in Windows?

Question

I have a GSM modem connected via USB. The modem creates 2 serial ports. The first is automatically attached to the modem, the second shows in Device Manager as "HUAWEI Mobile Connect - 3G PC UI Interface (COM6)"

The second port is used to get vital information from the modem, such as signal quality; to send and receive text messages; and a whole host of other functions.

I am writing an application that will wrap up some of the features provided by the second port. What I need is a sure fire method of identifying which COM port is the spare one. Iterating the ports and checking a response to "ATE0" is not sufficient. The modem's port is usually the lower numbered one, and when a dial up connection is not active, it will respond to "ATE0" the same as the second port.

What I was thinking of doing is iterating the ports and checking their friendly name, as it shows in Device Manager. That way I can link the port in my application to the port labelled "HUAWEI Mobile Connect - 3G PC UI Interface (COM6)" in Device Manager. I've just not found any information yet that will allow me to get that name programmatically.

Answer 1

A long time ago I wrote a utility for a client to do just this, but for a GPS rather than a modem.

I have just looked at it, and bits that jump-out as being possibly helpful are:

    GUID guid = GUID_DEVCLASS_PORTS;

SP_DEVICE_INTERFACE_DATA interfaceData;
ZeroMemory(&interfaceData, sizeof(interfaceData));
interfaceData.cbSize = sizeof(interfaceData);

SP_DEVINFO_DATA devInfoData;
ZeroMemory(&devInfoData, sizeof(devInfoData));
devInfoData.cbSize = sizeof(devInfoData);

if(SetupDiEnumDeviceInfo(
    hDeviceInfo,            // Our device tree
    nDevice,            // The member to look for
    &devInfoData
    ))
{
    DWORD regDataType;

    BYTE hardwareId[300];
    if(SetupDiGetDeviceRegistryProperty(hDeviceInfo, &devInfoData, SPDRP_HARDWAREID, &regDataType, hardwareId, sizeof(hardwareId), NULL))
    {
...

(You call this bit in a loop with incrementing nDevice)

and then

BYTE friendlyName[300];
        if(SetupDiGetDeviceRegistryProperty(hDeviceInfo, &devInfoData, SPDRP_FRIENDLYNAME, NULL, friendlyName, sizeof(friendlyName), NULL))
        {
            strFriendlyNames += (LPCTSTR)friendlyName;
            strFriendlyNames += '\n';
        }

which finds the name of the device.

Hopefully that will help you in the right direction.