Android Tutorial => Connect to Bluetooth device

Example

After you obtained BluetoothDevice, you can communicate with it. This kind of communication performed by using socket input\output streams:

Those are the basic steps for Bluetooth communication establishment:

1) Initialize socket:

 private BluetoothSocket _socket;
 //...
 public InitializeSocket(BluetoothDevice device){
    try {
        _socket = device.createRfcommSocketToServiceRecord(<Your app UDID>);
    } catch (IOException e) {
        //Error
    }
  }

2) Connect to socket:

try {
    _socket.connect();
} catch (IOException connEx) {
    try {
        _socket.close();
    } catch (IOException closeException) {
        //Error
    }
}

if (_socket != null && _socket.isConnected()) {
    //Socket is connected, now we can obtain our IO streams
}

3) Obtaining socket Input\Output streams

private InputStream _inStream;
private OutputStream _outStream;
//....
try {
    _inStream = _socket.getInputStream();
    _outStream =  _socket.getOutputStream();
} catch (IOException e) {
   //Error
}

Input stream - Used as incoming data channel (receive data from connected device)

Output stream - Used as outgoing data channel (send data to connected device)

After finishing 3rd step, we can receive and send data between both devices using previously initialized streams:

1) Receiving data (reading from socket input stream)

byte[] buffer = new byte[1024];  // buffer (our data)
int bytesCount; // amount of read bytes

while (true) {
    try {
        //reading data from input stream
        bytesCount = _inStream.read(buffer);
        if(buffer != null && bytesCount > 0)
        {
            //Parse received bytes
        }
    } catch (IOException e) {
        //Error
    }
}

2) Sending data (Writing to output stream)

public void write(byte[] bytes) {
    try {
        _outStream.write(bytes);
    } catch (IOException e) {
        //Error
    }
}

Of course, connection, reading and writing functionality should be done in a dedicated thread.
Sockets and Stream objects need to be

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