Pair bluetooth devices to a computer with 32feet .NET Bluetooth library

Question

If you want to know how to use 32feet.NET library to communicate with bluetooth devices, read the solution

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I am currently trying to communicat

Answer 1

I figured out how to solve my problems and my knowledge about Bluetooth connections is a bit bigger now. If someone else has problems with that, I provide my solution. The code examples represent the C# implementation of a bluetooth controller with the 32feet Bluetooth library.

Scanning

This means that devices in range are detected. My code:

// mac is mac address of local bluetooth device
BluetoothEndPoint localEndpoint = new BluetoothEndPoint(mac, BluetoothService.SerialPort);
// client is used to manage connections
BluetoothClient localClient = new BluetoothClient(localEndpoint);
// component is used to manage device discovery
BluetoothComponent localComponent = new BluetoothComponent(localClient);
// async methods, can be done synchronously too
localComponent.DiscoverDevicesAsync(255, true, true, true, true, null);
localComponent.DiscoverDevicesProgress += new EventHandler<DiscoverDevicesEventArgs>(component_DiscoverDevicesProgress);
localComponent.DiscoverDevicesComplete += new EventHandler<DiscoverDevicesEventArgs>(component_DiscoverDevicesComplete);

private void component_DiscoverDevicesProgress(object sender, DiscoverDevicesEventArgs e)
{
    // log and save all found devices
    for (int i = 0; i < e.Devices.Length; i++)
    {           
        if (e.Devices[i].Remembered)
        {
            Print(e.Devices[i].DeviceName + " (" + e.Devices[i].DeviceAddress + "): Device is known");
        }
        else
        {
            Print(e.Devices[i].DeviceName + " (" + e.Devices[i].DeviceAddress + "): Device is unknown");
        }
        this.deviceList.Add(e.Devices[i]);         
    }
}

private void component_DiscoverDevicesComplete(object sender, DiscoverDevicesEventArgs e)
{
    // log some stuff
}

Pairing

This means that devices get coupled with the local bluetooth device. This needs to be done once by entering a code of both sides. Can be done via code so that the user doesn't even notice that a device was added. My code for this purpose:

// get a list of all paired devices
BluetoothDeviceInfo[] paired = localClient.DiscoverDevices(255, false, true, false, false);
// check every discovered device if it is already paired 
foreach (BluetoothDeviceInfo device in this.deviceList)
{
    bool isPaired = false;
    for (int i = 0; i < paired.Length; i++)
    {
        if (device.Equals(paired[i]))
        {
            isPaired = true;
            break;
        }
    }

    // if the device is not paired, pair it!
    if (!isPaired)
    {
        // replace DEVICE_PIN here, synchronous method, but fast
        isPaired = BluetoothSecurity.PairRequest(device.DeviceAddress, DEVICE_PIN);
        if (isPaired)
        {
            // now it is paired
        }
        else
        {
            // pairing failed
        }
    }
}

Connecting

This means establishing a connection and exchanging of data. Again some code:

// check if device is paired
if (device.Authenticated)
{
    // set pin of device to connect with
    localClient.SetPin(DEVICE_PIN);
    // async connection method
    localClient.BeginConnect(device.DeviceAddress, BluetoothService.SerialPort, new AsyncCallback(Connect), device);
}

// callback
private void Connect(IAsyncResult result)
{
    if (result.IsCompleted)
    {
        // client is connected now :)
    }
}

If you keep the order scan, pair, connect, everything should work fine. To send or receive data, use the GetStream() method of the BluetoothClient. It provides a network stream that can be manipulated.

Receiving a connection

If you want another device to connect with your device you need to listen to incoming connection requests. This only works if the device have already been paired before. My code:

BluetoothListener l = new BluetoothListener(LOCAL_MAC, BluetoothService.SerialPort);
l.Start(10);
l.BeginAcceptBluetoothClient(new AsyncCallback(AcceptConnection), l);

void AcceptConnection(IAsyncResult result){
    if (result.IsCompleted){
        BluetoothClient remoteDevice = ((BluetoothListener)result.AsyncState).EndAcceptBluetoothClient(result);    
    }    
}

Replace LOCAL_MAC with a valid BluetoothAddress (e.g. by using BluetoothAddress.Parse();). After the devices are connected they can exchange messages via the underlying stream. If the connection does not work there might be authentication issues, so try setting the local device pin in the listener (l.SetPin(LOCAL_MAC, MY_PASSWORD);