I have a couple problems regarding creating a bluetooth server and client for a multiplayer game I'm making.
The first problem I have is searching for devices. Google provides following code:
// Create a BroadcastReceiver for ACTION_FOUND
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
// When discovery finds a device
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
// Get the BluetoothDevice object from the Intent
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
// Add the name and address to an array adapter to show in a ListView
mArrayAdapter.add(device.getName() + "\n" + device.getAddress());
}
}
};
// Register the BroadcastReceiver
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
registerReceiver(mReceiver, filter); // Don't forget to unregister during onDestroy
But I can't find where mArrayAdapter is defined or how it should look like.
Second question I have is, when I have a server running on my device, do I have to connect to it also, or does only the other phone have to connect and my server acts as a client and a server?
Third question I have is how to connect to the server. Again, google provides this code:
private class ConnectThread extends Thread {
private final BluetoothSocket mmSocket;
private final BluetoothDevice mmDevice;
public ConnectThread(BluetoothDevice device) {
// Use a temporary object that is later assigned to mmSocket,
// because mmSocket is final
BluetoothSocket tmp = null;
mmDevice = device;
// Get a BluetoothSocket to connect with the given BluetoothDevice
try {
// MY_UUID is the app's UUID string, also used by the server code
tmp = device.createRfcommSocketToServiceRecord(MY_UUID);
} catch (IOException e) { }
mmSocket = tmp;
}
public void run() {
// Cancel discovery because it will slow down the connection
mBluetoothAdapter.cancelDiscovery();
try {
// Connect the device through the socket. This will block
// until it succeeds or throws an exception
mmSocket.connect();
} catch (IOException connectException) {
// Unable to connect; close the socket and get out
try {
mmSocket.close();
} catch (IOException closeException) { }
return;
}
// Do work to manage the connection (in a separate thread)
manageConnectedSocket(mmSocket);
}
/** Will cancel an in-progress connection, and close the socket */
public void cancel() {
try {
mmSocket.close();
} catch (IOException e) { }
}
}
How do I create and use this class, and what variable should I pass for BluetoothDevice device in the constructor?
Thanks for your help :)
You can see from mArrayAdapter.add(device.getName() + "\n" + device.getAddress()); that a String is added. So it will be defined as:
ArrayAdapter<String> mNewDevicesArrayAdapter = new ArrayAdapter<String>(this, R.layout.bluetooth_device_name);
Where did you get your code from? The complete code you can find in DeviceListActivity.java of the BluetoothChat example app which comes with the SDk for many versions again and again.
For your second question: One app on a device makes the device visible. The other app on the other device scanns for neighbouring devices and tries to connect. Then both devices have to agree.
I advise you to do the BluetoothChat app from tne examples first. It works out of the box.
Related
I tried to create a simple android application to connect to my ELM327 device to get some car diagnostic data. But I wasn't able to set up the bluetooth connection b/t my android phone and my ELM327 device.
My code is very simple as below:
public class Bluetooth {
protected BluetoothAdapter mBluetoothAdapter= BluetoothAdapter.getDefaultAdapter();
private ConnectThread mConnectThread = null;
private AcceptThread mAcceptThread = null;
private WorkerThread mWorkerThread = null;
private BluetoothDevice mOBDDevice = null;
private BluetoothSocket mSocket = null;
private String uuid;
Bluetooth() {
mBluetoothAdapter= BluetoothAdapter.getDefaultAdapter();
Set<BluetoothDevice> pairedDevices;
if (mBluetoothAdapter == null || !mBluetoothAdapter.isEnabled())
return;
pairedDevices = mBluetoothAdapter.getBondedDevices();
if (pairedDevices.size() > 0) {
// There are paired devices. Get the name and address of each paired device.
for (BluetoothDevice device : pairedDevices) {
String deviceName = device.getName();
String deviceHardwareAddress = device.getAddress(); // MAC address
//TODO: check whether this is OBD and whether it is connected
//by sending a command and check response
if (deviceName.contains("OBD")) {
mOBDDevice = device;
uuid = device.getUuids()[0].toString();
break;
}
}
}
mBluetoothAdapter.cancelDiscovery();
}
/**
* Start the chat service. Specifically start AcceptThread to begin a session
* in listening (server) mode. Called by the Activity onResume()
*/
public synchronized void connect()
{
try {
// Get a BluetoothSocket to connect with the given BluetoothDevice.
// MY_UUID is the app's UUID string, also used in the server code.
mSocket = mOBDDevice.createRfcommSocketToServiceRecord(UUID.fromString(uuid));
} catch (IOException e) {
Log.e(TAG, "Socket's create() method failed", e);
}
try {
// Connect to the remote device through the socket. This call blocks
// until it succeeds or throws an exception.
mSocket.connect();
} catch (IOException connectException) {
// Unable to connect; close the socket and return.
try {
mSocket.close();
} catch (IOException closeException) {
Log.e(TAG, "Could not close the client socket", closeException);
}
return;
}
}
}
In the mainactivity, I will first new a Bluetooth class then call bluetooth.connect():
mBluetooth = new Bluetooth();
mBluetooth.connect();
When I debug the program, I was able to get my ELM327 bluetooth device by querying all the bonded devices with a name of "OBD". I also was able to get the device's uuid and create a socket using createRfcommSocketToServiceRecord. But in the connect function, mSocket.connect() always fail with a return value of -1 and get a IOexception.
My questions are:
When my android application connect to the ELM327 device, my android phone is the bluetooth client and my ELM327 device is the bluetooth server, is this understanding correct?
Is there a server program running on my ELM327 device listening and accept incoming connection? Is this defined behavior of ELM327 protocol?
Any idea why mSocket.connect()has failed? Any idea on how to look into this issue? Or any obvious error in my program? Thanks.
problem solved. see source codes below:
public synchronized void connect() throws IOException {
try {
// Get a BluetoothSocket to connect with the given BluetoothDevice.
// MY_UUID is the app's UUID string, also used in the server code.
mSocket = mOBDDevice.createRfcommSocketToServiceRecord(UUID.fromString(uuid));
} catch (IOException e) {
Log.e(TAG, "Socket's create() method failed", e);
}
try {
// Connect to the remote device through the socket. This call blocks
// until it succeeds or throws an exception.
mSocket.connect();
} catch (IOException e1) {
Log.e(TAG, "There was an error while establishing Bluetooth connection. Falling back..", e1);
Class<?> clazz = mSocket.getRemoteDevice().getClass();
Class<?>[] paramTypes = new Class<?>[]{Integer.TYPE};
try {
Method m = clazz.getMethod("createRfcommSocket", paramTypes);
Object[] params = new Object[]{Integer.valueOf(1)};
mFallbackSocket = (BluetoothSocket) m.invoke(mSocket.getRemoteDevice(), params);
mFallbackSocket.connect();
mSocket.close();
mSocket = mFallbackSocket;
} catch (Exception e2) {
Log.e(TAG, "Couldn't fallback while establishing Bluetooth connection.", e2);
mSocket.close();
//throw new IOException();
}
}
inputStream = mSocket.getInputStream();
outputStream = mSocket.getOutputStream();
}
I don't know much about Android, although I know about OBD2 and the lot.
It depends on the type of your adapter. If you have a WiFi adapter, you can consider the adapter being the server and you the client. You connect to a socket and then read from it. In the case of a Bluetooth adapter, it's different. If you connect via rfcomm, it's a serial protocol and neither is the server nor the client. If you connect via BTLE, the OBD2 dongle is the Peripheral and you are the Central.
On WiFi adapters, yes. This behavior is not part of ELM327 though. ELM327 only specifies the serial commands. How you transfer these is not part of the spec, since it happens on the layer above (WiFi, rfcomm, BTLE, USB, etc.).
Are you sure that rfcomm works via the socket interface? It's a serial interface, so I would have expected file-like operations.
I checked the developer site and got some help to develop the Bluetooth chat app. I'm not able to connect to other devices. I have used the UUID which was mentioned in the developer site Bluetooth chat example. I know it should be unique but I don't know how to find. Please let me know. I am using Samsung Galaxy J7.
The Bluetooth Chat sample helps how to do a similar app based on the sample.
This application allows two Android devices to carry out two-way text chat over Bluetooth. It demonstrates all the fundamental Bluetooth API capabilites, such as: (1) Scanning for other Bluetooth devices (2) Querying the local Bluetooth adapter for paired Bluetooth devices (3) Establishing RFCOMM channels/sockets (4) Connecting to a remote device (5) Transfering data over Bluetooth
The sample isn't easy to learn you'll need some help by me.
How to make your Bluetooth Chat app based on sample
The Bluetooth connection works in the Client and Server method, even if you're connecting 2 devices, all devices will be both Client and Server (devices connect to others and also accept connections from others).
The UUIDs
UUID stands for Universally Unique Identifier, your UUID must be unique, however, uniqueness isn't always guaranteed and the chances of generating a equal UUID are so low you don't need to worry about the uniqueness. If you want, google "UUID generator" and you'll find sites like this.
Once you generated your UUID, use the same UUID for Client and Server.
Connect to other devices
To connect to other devices, you'll have to enumerate the paired devices in the first place, the BluetoothAdapter contains everything for initial setup. The android.bluetooth.* package contains everything for your app.
BluetoothAdapter is a Singleton, so you can call the method BluetoothAdapter.getDefaultAdapter() many times without making too much instances.
BluetoothAdapter.getDefaultAdapter()
Let's assign mBluetoothAdapter as BluetoothAdapter.getDefaultAdapter().
Make sure Bluetooth is on, if Bluetooth was off, let's turn on.
if (!mBluetoothAdapter.isEnabled()) mBluetoothAdapter.enable();
It will take a few seconds to turn the Bluetooth on.
Enumerate paired devices
Let's enumerate the paired devices, the BluetoothDevice contains information about a specific device, "bonded" means "paired".
List<BluetoothDevice> devices = new ArrayList<>();
for (BluetoothDevice device : mBluetoothAdapter.getBondedDevices()) {
devices.add(device);
}
//Let's add the bonded devices to an ListView
MyBluetoothAdapter adapter = new MyBluetoothAdapter(this, devices);
mListView.setAdapter(adapter);
The MyBluetoothAdapter is an example, you'll need to make your own ArrayAdapter to fit your needs.
Connect to device
When some item is selected, Bluetooth will connect to the device, to prevent UI freeze, the connection will be made in the background using a different Thread.
BluetoothDevice device = yourMethodToGetTheDevice();
ConnectThread mConnectThread = new ConnectThread(device);
mConnectThread.start();
The ConnectThread code is here (I recommend to make an inner class to access parent class method):
The Bluetooth protocol that the sample uses is RFCOMM. THe mUUID is the UUID generated with the website mentioned.
private class ConnectThread extends Thread {
public ConnectThread(BluetoothDevice device) {
try {
mBluetoothSocket = device.createRfcommSocketToServiceRecord(mUUID);
} catch (IOException e) {
Log.e(TAG, e.getMessage(), e);
}
}
#Override
public void run() {
try {
Log.i(TAG, "Connecting...");
mBluetoothSocket.connect();
new ConnectedThread(mBluetoothSocket);
Log.i(TAG, "Connected");
} catch (IOException e) {
Log.e(TAG, e.getMessage(), e);
}
}
}
After the connection was established, you'll be able to send data.
Accept connection
To accept others' connections, you'll have to start a background thread that continuously checks for a connection.
private class AcceptThread extends Thread implements Closeable {
private BluetoothServerSocket mBluetoothServerSocket;
private volatile boolean running = true;
public AcceptThread(String name) {
mBluetoothServerSocket = mBluetoothAdapter.listenUsingRfcommWithServiceRecord(name, mUUID);
}
#Override
public void run() {
while (running) {
try {
mBluetoothSocket = mBluetoothServerSocket.accept();
if (mBluetoothSocket != null) {
close();
new ConnectedThread(mBluetoothSocket);
}
} catch (IOException e) {
Log.e(TAG, e.getMessage(), e);
break;
}
}
}
#Override
public void close() throws IOException {
mBluetoothServerSocket.close();
mBluetoothServerSocket = null;
running = false;
}
}
This code restricts the connection to a single device.
Communication
Once device is connected, the ConnectedThread will start.
private class ConnectedThread extends Thread implements Closeable {
private InputStream in;
private OutputStream out;
private volatile running = true;
public ConnectedThread(BluetoothSocket socket) {
try {
in = socket.getInputStream();
out = socket.getOutputStream();
} catch (IOException e) {
Log.e(TAG, e.getMessage(), e);
}
}
#Override
public void run() {
//The maximum amount of data to receive is 4KB, if you want to receive more data, you'll have to receive large data by chunks using while loop.
//Usually text isn't as large as 4KB.
byte[] data = new byte[4096];
int length;
while (running) {
try {
length = in.read(data);
String text = new String(data, 0, length);
Log.i(TAG, text);
} catch (IOException e) {
Log.e(TAG, e.getMessage(), e);
//Connection was lost
break;
}
}
}
public void write(byte[] data) throws IOException {
out.write(data);
}
}
To send data, like text, use this code:
mConnectedThread.write("MY TEXT".getBytes());
To receive data, use the code inside ConnectedThread and handle the String text variable.
I want to connect two cell phones using bluetooth with one of them being the host(listening for connections) and the other one initiating the connection. The code that initiates the connection works well and gets successfully connected to the other phone.
However the host gets stuck at socket.accept() because it doesn't detect the connection. The UUIDs are the same on both devices so I really have no clue about what the porblem is.
Here's the AcceptThread of the host:
private class AcceptThread extends Thread {
// The local server socket
private final BluetoothServerSocket mmServerSocket;
boolean running = true;
public AcceptThread() {
BluetoothServerSocket tmp = null;
// Create a new listening server socket
try {
tmp = mAdapter.listenUsingRfcommWithServiceRecord(NAME_SECURE, MY_UUID_SECURE);
} catch (IOException e) {
running = false;
Toast.makeText(getApplicationContext(), "socket failed: " + e.getMessage(), Toast.LENGTH_SHORT).show();
}
mmServerSocket = tmp;
}
public void run() {
setName("AcceptThread");
BluetoothSocket socket = null;
int state = getMState();
// Listen to the server socket if we're not connected
while (running) {
try {
// This is a blocking call and will only return on a
// successful connection or an exception
socket = mmServerSocket.accept();
} catch (IOException e) {
break;
}
// If a connection was accepted
if (socket != null) {
setState(STATE_CONNECTED);
Toast.makeText(getApplicationContext(), "Connected to: " + socket.getRemoteDevice().getName(), Toast.LENGTH_SHORT).show();
startConnectedThread(socket);
}
}
}
I can assure you the UUIDs that the both devices are using are the same: 00001101-0000-1000-8000-00805f9b34fb
Also I was testing this app on an older phone that has API Level lower than 15(as the host) and another phone(initiating) with API level 17. Can that cause connection issues??
I think that in a while loop should be running = false Once accepts is OK and also close acceptThread when starting ConnectedThread.
I would add check that mmServerSocket != Null
Alternatively, if that does not help to, add here more code (for ex. what is in StartConnectedThread)
I'm struggling with getting consistent bluetooth connections in a star topology. I have one master phone which is a Samsung Galaxy S4 running API 10. All of the phones that connect to the bluetoothserver socket on the S4 are LG Dynamic Tracfones also running API 10.
Over the past few days, I have seen a LOT of conflicting information on the web about what type of connection to use.
This is my current set up:
MASTER CODE
public void acceptConnection() {
.... (enable bt adapter) ...
// initializes a Bluetooth server socket
bluetoothServerSocket = bc.createBluetoothServerSocket();
//connection made to Master, discovery no longer needed
bluetoothAdapter.cancelDiscovery();
BluetoothSocket bluetoothSocket;
// loops until the thread is interrupted or an exception occurs
while (!isInterrupted()) {
try {
// attempts to accept the slave application's connection
bluetoothSocket = bluetoothServerSocket.accept();
} catch (IOException e) {
// prints out the exception's stack trace
e.printStackTrace();
Log.v("Default Thread", "Connection to slave failed.");
// breaks out of the while loop
return;
}
try {
... (enumerate all input and output streams, and all bt sockets) ...
} catch (IOException e) {
// prints out the exception's stack trace
e.printStackTrace();
}
}
This is the method that is called when creating a blueToothServerSocket, and this is where half of my confusion is. How should I listen on the adapter? Currently, I'm doing it insecurely.
public BluetoothServerSocket createBluetoothServerSocket() {
// gets the name of the application
String name = "PVCED";
// gets a common UUID for both the master and slave applications
UUID uuid = UUID.fromString("23ea856c-49da-11e4-9e35-164230d1df67");
// initializes an empty Bluetooth server socket
serverSocket = null;
try {
// creates a Bluetooth socket using a common UUID
serverSocket = bluetoothAdapter.listenUsingInsecureRfcommWithServiceRecord(name, uuid);
} catch (IOException e) {
// prints out the exception's stack trace
e.printStackTrace();
}
return serverSocket;
}
SLAVE CODE
And this is where the other half of my confusion is, how should I create a socket? Currently I'm doing it insecurely.
private BluetoothSocket createBluetoothSocket(Set<BluetoothDevice> pairedDevices) {
// gets a common UUID for both the master and slave applications
UUID uuid = UUID.fromString("23ea856c-49da-11e4-9e35-164230d1df67");
// initialises an empty Bluetooth socket
BluetoothSocket bluetoothSocket = null;
// checks to see if there are any paired devices
if (pairedDevices.size() > 0) {
// loops through each paired device
for (BluetoothDevice device : pairedDevices) {
// checks to see if the name of the paired device is MASTER
if (device.getName().equals("MASTER")) {
try {
master = device;
// creates a Bluetooth socket using a common UUID
//bluetoothSocket = master.createRfcommSocketToServiceRecord(uuid);
//Method m = master.getClass().getMethod("createRfcommSocketToServiceRecord", new Class[] {int.class});
//bluetoothSocket = (BluetoothSocket) m.invoke(master, 1);
bluetoothSocket = master.createInsecureRfcommSocketToServiceRecord(uuid);
} catch(Exception e){
Log.v("Connect Exception", e.getMessage());
}
}
}
}
//check if we paired succesfully to a master, if not, prompt user to do so.
if (master == null){
... (tell user to pair with master via toast) ...
}
return bluetoothSocket;
}
My logcat is often filled with errors such as "Bad File Descriptor", "Unable to start Service Discovery", or "Service Discovery has failed."
What is the best connection scheme to use for my scenario? If you guys need more details on how I'm enabling/disabling bt adapters, or closing bt connections, I can supply more code.
i want to pair Bluetooth with the confirmation from other side only..but i implemented a code and here no confirmation message send to other side ..so now how do i send confirmation message to other before pairing two devices via Bluetooth ..
i use this below code:
private class AcceptThread extends Thread {
// The local server socket
private final BluetoothServerSocket mmServerSocket;
public AcceptThread() {
BluetoothServerSocket tmp = null;
// Create a new listening server socket
try {
tmp = mAdapter
.listenUsingRfcommWithServiceRecord(NAME, MY_UUID);
} catch (IOException e) {
Log.e(TAG, "listen() failed", e);
}
mmServerSocket = tmp;
}
private class ConnectThread extends Thread {
private final BluetoothSocket mmSocket;
private final BluetoothDevice mmDevice;
public ConnectThread(BluetoothDevice device) {
mmDevice = device;
BluetoothSocket tmp = null;
// Get a BluetoothSocket for a connection with the given
// BluetoothDevice
try {
tmp = device.createRfcommSocketToServiceRecord(MY_UUID);
} catch (IOException e) {
Log.e(TAG, "create() failed", e);
}
mmSocket = tmp;
}
#Override
public void run() {
Log.i(TAG, "BEGIN mConnectThread");
setName("ConnectThread");
// Always cancel discovery because it will slow down a connection
mAdapter.cancelDiscovery();
// Make a connection to the BluetoothSocket
try {
// This is a blocking call and will only return on a
// successful connection or an exception
mmSocket.connect();
} catch (IOException e) {
connectionFailed();
// Close the socket
try {
mmSocket.close();
} catch (IOException e2) {
Log.e(TAG,"unable to close() socket during connection failure",
e2);
}
// Start the service over to restart listening mode
BluetoothChatService.this.start();
return;
}
so pls see my code and pls suggest me how to pair 2 devices only when authenticated from remote side...i am using api level 7
You cannot send a message to the other device as long as the two devices are not paired, because you need a BluetoothSocket for that, which cannot be obtained unless you have the device's MAC address.
But what's the problem with the pairing request? It will show only the first time, then you can always find the device among the paired devices (mBluetoothAdapter.getBondedDevices()).
Buuut, if it's absolutely necessary for you to get rid of the Pairing request dialog showing at the beginning on the both parts, then you may try use an insecure channel (create the server socket with listenUsingInsecureRfcommWithServiceRecord and the client socket with createInsecureRfcommSocketToServiceRecord). The problem here is that you'll have to perform a scan every time you need to connect to a device, as the devices are not paired.
Hope it suits you, goodluck.