Added in API level 5

BluetoothSocket

class BluetoothSocket : Closeable
kotlin.Any
   ↳ android.bluetooth.BluetoothSocket

A connected or connecting Bluetooth socket.

The interface for Bluetooth Sockets is similar to that of TCP sockets: java.net.Socket and java.net.ServerSocket. On the server side, use a BluetoothServerSocket to create a listening server socket. When a connection is accepted by the BluetoothServerSocket, it will return a new BluetoothSocket to manage the connection. On the client side, use a single BluetoothSocket to both initiate an outgoing connection and to manage the connection.

The most common type of Bluetooth socket is RFCOMM, which is the type supported by the Android APIs. RFCOMM is a connection-oriented, streaming transport over Bluetooth. It is also known as the Serial Port Profile (SPP).

To create a BluetoothSocket for connecting to a known device, use BluetoothDevice.createRfcommSocketToServiceRecord(). Then call connect() to attempt a connection to the remote device. This call will block until a connection is established or the connection fails.

To create a BluetoothSocket as a server (or "host"), see the BluetoothServerSocket documentation.

Once the socket is connected, whether initiated as a client or accepted as a server, open the IO streams by calling getInputStream and getOutputStream in order to retrieve java.io.InputStream and java.io.OutputStream objects, respectively, which are automatically connected to the socket.

BluetoothSocket is thread safe. In particular, #close will always immediately abort ongoing operations and close the socket.

Summary

Constants
static Int

L2CAP socket

static Int

RFCOMM socket

static Int

SCO socket

Public methods
Unit

Unit

Attempt to connect to a remote device.

Int

Get the type of the underlying connection.

InputStream!

Get the input stream associated with this socket.

Int

Get the maximum supported Receive packet size for the underlying transport.

Int

Get the maximum supported Transmit packet size for the underlying transport.

OutputStream!

Get the output stream associated with this socket.

BluetoothDevice!

Get the remote device this socket is connecting, or connected, to.

Boolean

Get the connection status of this socket, ie, whether there is an active connection with remote device.

String

Constants

TYPE_L2CAP

Added in API level 23
static val TYPE_L2CAP: Int

L2CAP socket

Value: 3

TYPE_RFCOMM

Added in API level 23
static val TYPE_RFCOMM: Int

RFCOMM socket

Value: 1

TYPE_SCO

Added in API level 23
static val TYPE_SCO: Int

SCO socket

Value: 2

Public methods

close

Added in API level 5
fun close(): Unit
Exceptions
java.lang.Exception if this resource cannot be closed
java.io.IOException if an I/O error occurs

connect

Added in API level 5
fun connect(): Unit

Attempt to connect to a remote device.

This method will block until a connection is made or the connection fails. If this method returns without an exception then this socket is now connected.

Creating new connections to remote Bluetooth devices should not be attempted while device discovery is in progress. Device discovery is a heavyweight procedure on the Bluetooth adapter and will significantly slow a device connection. Use android.bluetooth.BluetoothAdapter#cancelDiscovery() to cancel an ongoing discovery. Discovery is not managed by the Activity, but is run as a system service, so an application should always call android.bluetooth.BluetoothAdapter#cancelDiscovery() even if it did not directly request a discovery, just to be sure.

close can be used to abort this call from another thread.
For apps targeting Build.VERSION_CODES#S or or higher, this requires the Manifest.permission#BLUETOOTH_CONNECT permission which can be gained with android.app.Activity#requestPermissions(String[], int).
Requires android.Manifest.permission#BLUETOOTH_CONNECT

Exceptions
android.bluetooth.BluetoothSocketException in case of failure, with the corresponding error code.
java.io.IOException for other errors (eg: InputStream read failures etc.).

getConnectionType

Added in API level 23
fun getConnectionType(): Int

Get the type of the underlying connection.

Return
Int one of TYPE_RFCOMM, TYPE_SCO or TYPE_L2CAP

getInputStream

Added in API level 5
fun getInputStream(): InputStream!

Get the input stream associated with this socket.

The input stream will be returned even if the socket is not yet connected, but operations on that stream will throw IOException until the associated socket is connected.

Return
InputStream! InputStream

getMaxReceivePacketSize

Added in API level 23
fun getMaxReceivePacketSize(): Int

Get the maximum supported Receive packet size for the underlying transport. Use this to optimize the reads done on the input stream, as any call to read will return a maximum of this amount of bytes - or for some transports a multiple of this value.

Return
Int the maximum supported Receive packet size for the underlying transport.

getMaxTransmitPacketSize

Added in API level 23
fun getMaxTransmitPacketSize(): Int

Get the maximum supported Transmit packet size for the underlying transport. Use this to optimize the writes done to the output socket, to avoid sending half full packets.

Return
Int the maximum supported Transmit packet size for the underlying transport.

getOutputStream

Added in API level 5
fun getOutputStream(): OutputStream!

Get the output stream associated with this socket.

The output stream will be returned even if the socket is not yet connected, but operations on that stream will throw IOException until the associated socket is connected.

Return
OutputStream! OutputStream

getRemoteDevice

Added in API level 5
fun getRemoteDevice(): BluetoothDevice!

Get the remote device this socket is connecting, or connected, to.

Return
BluetoothDevice! remote device

isConnected

Added in API level 14
fun isConnected(): Boolean

Get the connection status of this socket, ie, whether there is an active connection with remote device.

Return
Boolean true if connected false if not connected

toString

Added in API level 5
fun toString(): String
Return
String a string representation of the object.