The Bluetooth APIs let applications:

• Scan for other Bluetooth devices
• Query the local Bluetooth adapter for paired Bluetooth devices
• Establish RFCOMM channels/sockets
• Connect to specified sockets on other devices
• Transfer data to and from other devices

Note: To perform Bluetooth communication using these APIs, an application must declare the {@link android.Manifest.permission#BLUETOOTH} permission. Some additional functionality, such as requesting device discovery and pairing also requires the {@link android.Manifest.permission#BLUETOOTH_ADMIN} permission.

Overview

Here's a basic introduction to the Bluetooth classes:

{@link android.bluetooth.BluetoothAdapter}

This represents the local Bluetooth adapter, which is essentially the entry-point to performing any interaction with Bluetooth. With it, you can discover other Bluetooth devices, query a list of bonded (paired) devices, initialize a {@link android.bluetooth.BluetoothDevice} using a known MAC address, and create a {@link android.bluetooth.BluetoothServerSocket} to listen for communications from other devices.

{@link android.bluetooth.BluetoothDevice}

This represents a remote Bluetooth device. Use this to request a connection with a remote device through a {@link android.bluetooth.BluetoothSocket} or query information about the device such as its name, address, class, and bonding state.

{@link android.bluetooth.BluetoothSocket}

This represents the interface for a Bluetooth socket (similar to a TCP client-side {@link java.net.Socket}). This is the connection point that allows an app to transfer data with another Bluetooth device via {@link java.io.InputStream} and {@link java.io.OutputStream}.

{@link android.bluetooth.BluetoothServerSocket}

This represents an open server socket that listens for incoming requests (similar to a TCP server-side {@link java.net.ServerSocket}). When attempting to connect two Android devices, one device will need to open a server socket with this class. When a connection is accepted, a new {@link android.bluetooth.BluetoothSocket} will be returned, which can be used to manage the connection and transfer data.

{@link android.bluetooth.BluetoothClass}

This represents the Bluetooth class for a device which describes general characteristics and capabilities of a device. This class and its subclasses don't provide any actual functionality. The sub-classes are entirely composed of constants for the device and service class definitions.

Example Procedure

For example, here's an pseudo-code procedure for discovering and connecting a remote device, and transfering data:

1. Register a {@link android.content.BroadcastReceiver} that accepts the {@link android.bluetooth.BluetoothDevice#ACTION_FOUND} Intent.
2. Call {@link android.bluetooth.BluetoothAdapter#getDefaultAdapter} to retrieve the Android system's local {@link android.bluetooth.BluetoothAdapter}.
3. Call {@link android.bluetooth.BluetoothAdapter#startDiscovery() BluetoothAdapter.startDiscovery()} to scan for local devices. This is where the BroadcastReceiver comes in; Android now scans for devices and will broadcast the {@link android.bluetooth.BluetoothDevice#ACTION_FOUND} Intent for each remote device discovered. The {@link android.content.BroadcastReceiver} you created will receive each Intent.
4. The {@link android.bluetooth.BluetoothDevice#ACTION_FOUND} Intent includes the {@link android.bluetooth.BluetoothDevice#EXTRA_DEVICE} Parcelable extra, which is a {@link android.bluetooth.BluetoothDevice} object. Extract this from the Intent and call {@link android.bluetooth.BluetoothDevice#createRfcommSocketToServiceRecord(java.util.UUID) BluetoothDevice.createRfcommSocketToServiceRecord()} to open a {@link android.bluetooth.BluetoothSocket} with a chosen remote device.
5. Call {@link android.bluetooth.BluetoothSocket#connect() BluetoothSocket.connect()} to connect with the remote device.
6. When successfully connected, call {@link android.bluetooth.BluetoothSocket#getInputStream() BluetoothSocket.getInputStream()} and/or {@link android.bluetooth.BluetoothSocket#getOutputStream() BluetoothSocket.getOutputStream()} to retreive an {@link java.io.InputStream} and {@link java.io.OutputStream}, respectively, which are hooked into the socket.
7. Use {@link java.io.InputStream#read(byte[]) InputStream.read()} and {@link java.io.OutputStream#write(byte[]) OutputStream.write()} to transfer data.

Note: Not all Android devices are guaranteed to have Bluetooth functionality.