How can I find out a COM port number of a bluetooth device in c#?

Question

My company developed a device that communicates with a PC via Bluetooth using a virtual COM port.

Now we need a user to pair a device with a PC (MS Windows OS) firs

Answer 1

I manage to get the bluetooth name and the COM port by fiddling the registry key

The pseudo code to obtain the bluetooth information is below:

• enumerate all the COM port available in the PNP
• obtain the device classGuid
• search the bluetooth address from the classGuid
• when the bluetooth address is known, the bluetooth name can be obtained from the this registry SYSTEM\CurrentControlSet\Services\BTHPORT\Parameters\Devices

The code is below, just call the GetBluetoothPort(), it will return a list of bluetooth devices, and you could connect them by passing the COM port number to the SerialPort class

public static string[] GetBluetoothPort()
{
    Regex regexPortName = new Regex(@"(COM\d+)");

    List portList = new List();

    ManagementObjectSearcher searchSerial = new ManagementObjectSearcher("SELECT * FROM Win32_PnPEntity");

    foreach (ManagementObject obj in searchSerial.Get()) {
        string name = obj["Name"] as string;
        string classGuid = obj["ClassGuid"] as string;
        string deviceID = obj["DeviceID"] as string;

        if (classGuid != null && deviceID != null) {
            if (String.Equals(classGuid, "{4d36e978-e325-11ce-bfc1-08002be10318}", StringComparison.InvariantCulture)) {
                string[] tokens = deviceID.Split('&');

                if (tokens.Length >= 4) {
                    string[] addressToken = tokens[4].Split('_');
                    string bluetoothAddress = addressToken[0];

                    Match m = regexPortName.Match(name);
                    string comPortNumber = "";
                    if (m.Success) {
                        comPortNumber = m.Groups[1].ToString();
                    }

                    if (Convert.ToUInt64(bluetoothAddress, 16) > 0) {
                        string bluetoothName = GetBluetoothRegistryName(bluetoothAddress);
                        portList.Add(String.Format("{0} {1} ({2})", bluetoothName, bluetoothAddress, comPortNumber));
                    }
                }
            }                    
        }
    }

    return portList.ToArray();
}

private static string GetBluetoothRegistryName(string address)
{
    string deviceName = "";

    string registryPath = @"SYSTEM\CurrentControlSet\Services\BTHPORT\Parameters\Devices";
    string devicePath = String.Format(@"{0}\{1}", registryPath, address);

    using (RegistryKey key = Registry.LocalMachine.OpenSubKey(devicePath)) {
        if (key != null) {
            Object o = key.GetValue("Name");

            byte[] raw = o as byte[];

            if (raw != null) {
                deviceName = Encoding.ASCII.GetString(raw);
            }
        }
    }

    return deviceName;
}