IOException read failed socket might closed - Bluetooth on Android 4 3

Question

Currently I am trying to deal with a strange Exception when opening a BluetoothSocket on my Nexus 7  2012   with Android 4 3  Build JWR66Y  I guess the second 4 3 update   I have seen some related postings  e g  https   stackoverflow com questions 13648373 bluetoothsocket-connect-throwing-exception-read-failed   but none seems to provide a workaround for this issue  Also  as suggested in these threads  re-pairing does not help  and constantly trying to connect  through a stupid loop  also has no effect   I am dealing with an embedded device  a noname OBD-II car adapter  similar to http   images04 olx com ui 15 53 76 1316534072 254254776 2-OBD-II-BLUTOOTH-ADAPTERSCLEAR-CHECK-ENGINE-LIGHTS-WITH-YOUR-PHONE-Oceanside jpg   My Android 2 3 7 phone does not have any issues connecting  and the Xperia of a colleague  Android 4 1 2  also works  Another Google Nexus  I dont know if  One  or  S   but not  4   also fails with Android 4 3   Here is the Snippet of the connection establishment  It is running in its own Thread  created within a Service   private class ConnectThread extends Thread        private static final UUID EMBEDDED BOARD SPP   UUID          fromString  00001101-0000-1000-8000-00805F9B34FB         private BluetoothAdapter adapter      private boolean secure      private BluetoothDevice device      private List lt UUID gt  uuidCandidates      private int candidate      protected boolean started       public ConnectThread BluetoothDevice device  boolean secure            logger info  initiliasing connection to device   device getName           device getAddress             adapter   BluetoothAdapter getDefaultAdapter            this secure   secure          this device   device           setName  BluetoothConnectThread             if   startQueryingForUUIDs                  this uuidCandidates   Collections singletonList EMBEDDED BOARD SPP               this start              else              logger info  Using UUID discovery mechanism                                     it will start upon the broadcast receive otherwise                        private boolean startQueryingForUUIDs             Class lt   gt  cl   BluetoothDevice class           Class lt   gt    par               Method fetchUuidsWithSdpMethod          try               fetchUuidsWithSdpMethod   cl getMethod  fetchUuidsWithSdp   par             catch  NoSuchMethodException e                logger warn e getMessage                 return false                     Object   args               try               BroadcastReceiver receiver   new BroadcastReceiver                      Override                 public void onReceive Context context  Intent intent                        BluetoothDevice deviceExtra   intent getParcelableExtra  android bluetooth device extra DEVICE                        Parcelable   uuidExtra   intent getParcelableArrayExtra  android bluetooth device extra UUID                         uuidCandidates   new ArrayList lt UUID gt                         for  Parcelable uuid   uuidExtra                            uuidCandidates add UUID fromString uuid toString                                                 synchronized  ConnectThread this                            if   ConnectThread this started                                ConnectThread this start                                ConnectThread this started   true                              unregisterReceiver this                                                                                                  registerReceiver receiver  new IntentFilter  android bleutooth device action UUID                 registerReceiver receiver  new IntentFilter  android bluetooth device action UUID                  fetchUuidsWithSdpMethod invoke device  args             catch  IllegalArgumentException e                logger warn e getMessage                 return false            catch  IllegalAccessException e                logger warn e getMessage                 return false            catch  InvocationTargetException e                logger warn e getMessage                 return false                                return true             public void run             boolean success   false          while  selectSocket                   if  bluetoothSocket    null                    logger warn  Socket is null  Cancelling                     deviceDisconnected                    openTroubleshootingActivity TroubleshootingActivity BLUETOOTH EXCEPTION                                 Always cancel discovery because it will slow down a connection             adapter cancelDiscovery                    Make a connection to the BluetoothSocket             try                      This is a blocking call and will only return on a                    successful connection or an exception                 bluetoothSocket connect                    success   true                  break                 catch  IOException e                       Close the socket                 try                       shutdownSocket                      catch  IOException e2                        logger warn e2 getMessage    e2                                                      if  success                deviceConnected              else               deviceDisconnected                openTroubleshootingActivity TroubleshootingActivity BLUETOOTH EXCEPTION                        private boolean selectSocket             if  candidate  gt   uuidCandidates size                  return false                     BluetoothSocket tmp          UUID uuid   uuidCandidates get candidate             logger info  Attempting to connect to SDP    uuid           try               if  secure                    tmp   device createRfcommSocketToServiceRecord                          uuid                 else                   tmp   device createInsecureRfcommSocketToServiceRecord                          uuid                             bluetoothSocket   tmp              return true            catch  IOException e                logger warn e getMessage    e                      return false             The code is failing at bluetoothSocket connect    I am getting a java io IOException  read failed  socket might closed  read ret  -1  This is the corresponding source at GitHub  https   github com android platform frameworks base blob android-4 3 r2 core java android bluetooth BluetoothSocket java L504 Its called through readInt    called from https   github com android platform frameworks base blob android-4 3 r2 core java android bluetooth BluetoothSocket java L319  Some metadata dump of the used socket resulted in the following information  These are exactly the same on Nexus 7 and my 2 3 7 phone   Bluetooth Device  OBDII  Address  11 22 33 DD EE FF Bond state  12  bonded  Type  1 Class major version  7936 Class minor version  7936 Class Contents  0 Contents  0   I have some other OBD-II adapters  more expansives  and they all work  Is there any chance  that I am missing something or might this be a bug in Android

User · Answer

Bluetooth devices can operate in both classic and LE mode at the same time. Sometimes they use a different MAC address depending on which way you are connecting. Calling socket.connect() is using Bluetooth Classic, so you have to make sure the device you got when you scanned was really a classic device.

It's easy to filter for only Classic devices, however:

if(BluetoothDevice.DEVICE_TYPE_LE == device.getType()){ //socket.connect() }

Without this check, it's a race condition as to whether a hybrid scan will give you the Classic device or the BLE device first. It may appear as intermittent inability to connect, or as certain devices being able to connect reliably while others seemingly never can.

User · Answer

Even i had the same problem  finally understand my issue   i was trying to connect from  out of range  Bluetooth coverage range

User · Answer

If another part of your code has already made a connection with the same socket and UUID  you get this error

User · Answer

i also faced with this problem you could solve it in 2 ways   as mentioned earlier use reflection to create the socket Second one is   client is looking for a server with given UUID and if your server isn t running parallel to client then this happens  Create a server with given client UUID and then listen and accept the client from server side It will work

User · Answer

I ran into this problem and fixed it by closing the input and output streams before closing the socket  Now I can disconnect and connect again with no issues   https   stackoverflow com a 3039807 5688612  In Kotlin   fun disconnect         bluetoothSocket inputStream close       bluetoothSocket outputStream close       bluetoothSocket close

User · Answer

In case somebody is having issues with Kotlin  I had to follow the accepted answer with some variations   fun print view  View  text  String        var adapter   BluetoothAdapter getDefaultAdapter        var pairedDevices   adapter getBondedDevices       var uuid   UUID fromString  00001101-0000-1000-8000-00805F9B34FB       if  pairedDevices size  gt  0            for  device in pairedDevices                var s   device name             if  device getName   equals printerName  ignoreCase   true                     Thread                       var socket   device createInsecureRfcommSocketToServiceRecord uuid                      var clazz   socket remoteDevice javaClass                     var paramTypes   arrayOf lt Class lt   gt  gt  Integer TYPE                      var m   clazz getMethod  createRfcommSocket    paramTypes                      var fallbackSocket   m invoke socket remoteDevice  Integer valueOf 1   as BluetoothSocket                     try                           fallbackSocket connect                           var stream   fallbackSocket outputStream                         stream write text toByteArray Charset forName  UTF-8                           catch  e  Exception                            e printStackTrace                           Snackbar make view   An error occurred   Snackbar LENGTH SHORT  show                                           start                                     Hope it helps

User · Answer

well  i had the same problem with my code  and it s because since android 4 2 bluetooth stack has changed  so my code was running fine on devices with android  lt  4 2   on the other devices i was getting the famous exception  read failed  socket might closed or timeout  read ret  -1   The problem is with the socket mPort parameter  When you create your socket using socket   device createRfcommSocketToServiceRecord SERIAL UUID     the mPort gets integer value  -1   and this value seems doesn t work for android   4 2   so you need to set it to  1   The bad news is that createRfcommSocketToServiceRecord only accepts UUID as parameter and not mPort so we have to use other aproach  The answer posted by  matthes also worked for me  but i simplified it  socket   BluetoothSocket  device getClass   getMethod  createRfcommSocket   new Class    int class   invoke device 1    We need to use both socket attribs   the second one as a fallback    So the code is  for connecting to a SPP on an ELM327 device    BluetoothAdapter btAdapter   BluetoothAdapter getDefaultAdapter         if  btAdapter isEnabled              SharedPreferences prefs btdev   getSharedPreferences  btdev   0           String btdevaddr prefs btdev getString  btdevaddr                 if  btdevaddr                               BluetoothDevice device   btAdapter getRemoteDevice btdevaddr                UUID SERIAL UUID   UUID fromString  00001101-0000-1000-8000-00805f9b34fb       bluetooth serial port service               UUID SERIAL UUID   device getUuids   0  getUuid      if you don t know the UUID of the bluetooth device service  you can get it like this from android cache              BluetoothSocket socket   null               try                   socket   device createRfcommSocketToServiceRecord SERIAL UUID                 catch  Exception e   Log e     Error creating socket                  try                   socket connect                    Log e     Connected                  catch  IOException e                    Log e    e getMessage                     try                       Log e     trying fallback                            socket   BluetoothSocket  device getClass   getMethod  createRfcommSocket   new Class    int class   invoke device 1                       socket connect                         Log e     Connected                                   catch  Exception e2                     Log e      Couldn t establish Bluetooth connection                                                     else                       Log e     BT device not selected

User · Answer

On newer versions of Android  I was receiving this error because the adapter was still discovering when I attempted to connect to the socket  Even though I called the cancelDiscovery method on the Bluetooth adapter  I had to wait until the callback to the BroadcastReceiver s onReceive   method was called with the action BluetoothAdapter ACTION DISCOVERY FINISHED   Once I waited for the adapter to stop discovery  then the connect call on the socket succeeded

User · Answer

Well  I have actually found the problem   The most people who try to make a connection using socket Connect    get an exception called Java IO IOException  read failed  socket might closed  read ret  -1   In some cases it also depends on your Bluetooth device  because there are two different types of Bluetooth  namely BLE  low energy  and Classic   If you want to check the type of your Bluetooth device is  here s the code           String checkType          var listDevices   BluetoothAdapter BondedDevices          if  listDevices Count  gt  0                        foreach  var btDevice in listDevices                                if btDevice Name     MOCUTE-032 B52-CA7E                                         checkType   btDevice Type ToString                        Console WriteLine checkType                                               I ve been trying for days to solve the problem  but since today I have found the problem  The solution from  matthes has unfortunately still a few issues as he said already  but here s my solution   At the moment I work in Xamarin Android  but this should also work for other platforms   SOLUTION  If there is more than one paired device  then you should remove the other paired devices  So keep only the one that you want to connect  see the right image       In the left image you see that I have two paired devices  namely  MOCUTE-032 B52-CA7E  and  Blue Easy   That s the issue  but I have no idea why that problem occurs  Maybe the Bluetooth protocol is trying to get some information from another Bluetooth device   However  the socket Connect    works great right now  without any problems  So I just wanted to share this  because that error is really annoying   Good luck

User · Answer

By adding filter action my problem resolved      Register for broadcasts when a device is discovered     IntentFilter intentFilter   new IntentFilter        intentFilter addAction BluetoothDevice ACTION FOUND       intentFilter addAction BluetoothAdapter ACTION DISCOVERY STARTED       intentFilter addAction BluetoothAdapter ACTION DISCOVERY FINISHED       registerReceiver mReceiver  intentFilter

User · Answer

I have finally found a workaround  The magic is hidden under the hood of the BluetoothDevice class  see https   github com android platform frameworks base blob android-4 3 r2 core java android bluetooth BluetoothDevice java L1037    Now  when I receive that exception  I instantiate a fallback BluetoothSocket  similar to the source code below  As you can see  invoking the hidden method createRfcommSocket via reflections  I have no clue why this method is hidden  The source code defines it as public though     Class lt   gt  clazz   tmp getRemoteDevice   getClass    Class lt   gt    paramTypes   new Class lt   gt     Integer TYPE    Method m   clazz getMethod  createRfcommSocket   paramTypes   Object   params   new Object    Integer valueOf 1     fallbackSocket    BluetoothSocket  m invoke tmp getRemoteDevice    params   fallbackSocket connect      connect   then does not fail any longer  I have experienced a few issues still  Basically  this sometimes blocks and fails  Rebooting the SPP-Device  plug off   plug in  helps in such cases  Sometimes I also get another Pairing request after connect   even when the device is already bonded   UPDATE   here is a complete class  containing some nested classes  for a real implementation these could be held as seperate classes   import java io IOException  import java io InputStream  import java io OutputStream  import java lang reflect Method  import java util List  import java util UUID   import android bluetooth BluetoothAdapter  import android bluetooth BluetoothDevice  import android bluetooth BluetoothSocket  import android util Log   public class BluetoothConnector        private BluetoothSocketWrapper bluetoothSocket      private BluetoothDevice device      private boolean secure      private BluetoothAdapter adapter      private List lt UUID gt  uuidCandidates      private int candidate                    param device the device         param secure if connection should be done via a secure socket         param adapter the Android BT adapter         param uuidCandidates a list of UUIDs  if null or empty  the Serial PP id is used             public BluetoothConnector BluetoothDevice device  boolean secure  BluetoothAdapter adapter              List lt UUID gt  uuidCandidates            this device   device          this secure   secure          this adapter   adapter          this uuidCandidates   uuidCandidates           if  this uuidCandidates    null    this uuidCandidates isEmpty                  this uuidCandidates   new ArrayList lt UUID gt                 this uuidCandidates add UUID fromString  00001101-0000-1000-8000-00805F9B34FB                          public BluetoothSocketWrapper connect   throws IOException           boolean success   false          while  selectSocket                  adapter cancelDiscovery                 try                   bluetoothSocket connect                    success   true                  break                catch  IOException e                      try the fallback                 try                       bluetoothSocket   new FallbackBluetoothSocket bluetoothSocket getUnderlyingSocket                         Thread sleep 500                                         bluetoothSocket connect                        success   true                      break                      catch  FallbackException e1                        Log w  BT    Could not initialize FallbackBluetoothSocket classes    e                     catch  InterruptedException e1                        Log w  BT   e1 getMessage    e1                     catch  IOException e1                        Log w  BT    Fallback failed  Cancelling    e1                                                      if   success                throw new IOException  Could not connect to device     device getAddress                        return bluetoothSocket             private boolean selectSocket   throws IOException           if  candidate  gt   uuidCandidates size                  return false                     BluetoothSocket tmp          UUID uuid   uuidCandidates get candidate              Log i  BT    Attempting to connect to Protocol     uuid           if  secure                tmp   device createRfcommSocketToServiceRecord uuid             else               tmp   device createInsecureRfcommSocketToServiceRecord uuid                     bluetoothSocket   new NativeBluetoothSocket tmp            return true             public static interface BluetoothSocketWrapper            InputStream getInputStream   throws IOException           OutputStream getOutputStream   throws IOException           String getRemoteDeviceName             void connect   throws IOException           String getRemoteDeviceAddress             void close   throws IOException           BluetoothSocket getUnderlyingSocket                 public static class NativeBluetoothSocket implements BluetoothSocketWrapper            private BluetoothSocket socket           public NativeBluetoothSocket BluetoothSocket tmp                this socket   tmp                      Override         public InputStream getInputStream   throws IOException               return socket getInputStream                        Override         public OutputStream getOutputStream   throws IOException               return socket getOutputStream                        Override         public String getRemoteDeviceName                 return socket getRemoteDevice   getName                        Override         public void connect   throws IOException               socket connect                        Override         public String getRemoteDeviceAddress                 return socket getRemoteDevice   getAddress                        Override         public void close   throws IOException               socket close                        Override         public BluetoothSocket getUnderlyingSocket                 return socket                        public class FallbackBluetoothSocket extends NativeBluetoothSocket            private BluetoothSocket fallbackSocket           public FallbackBluetoothSocket BluetoothSocket tmp  throws FallbackException               super tmp               try                             Class lt   gt  clazz   tmp getRemoteDevice   getClass                  Class lt   gt    paramTypes   new Class lt   gt     Integer TYPE                 Method m   clazz getMethod  createRfcommSocket   paramTypes                 Object   params   new Object    Integer valueOf 1                  fallbackSocket    BluetoothSocket  m invoke tmp getRemoteDevice    params                             catch  Exception e                                throw new FallbackException e                                     Override         public InputStream getInputStream   throws IOException               return fallbackSocket getInputStream                        Override         public OutputStream getOutputStream   throws IOException               return fallbackSocket getOutputStream                         Override         public void connect   throws IOException               fallbackSocket connect                         Override         public void close   throws IOException               fallbackSocket close                          public static class FallbackException extends Exception                                                private static final long serialVersionUID   1L           public FallbackException Exception e                super e

User · Answer

I ve had this problem and the solution was to use the special magic GUID               val id  UUID   UUID fromString  00001101-0000-1000-8000-00805F9B34FB      Any other GUID doesn t work              val device  BluetoothDevice   bta   bondedDevices first   z - gt  z name    deviceName                bts   device createRfcommSocketToServiceRecord id     mPort is -1             bts  connect                  Start processing thread    I suspect that these are the UUIDs that work   var did  Array lt ParcelUuid  gt    device uuids   However  I have not tried them all

User · Answer

I had the same symptoms as described here  I could connect once to a bluetooth printer but subsequent connects failed with  socket closed  no matter what I did   I found it a bit strange that the workarounds described here would be necessary  After going through my code I found that I had forgot to close the socket s InputStream and OutputSteram and not terminated the ConnectedThreads properly   The ConnectedThread I use is the same as in the example here   http   developer android com guide topics connectivity bluetooth html  Note that ConnectThread and ConnectedThread are two different classes   Whatever class that starts the ConnectedThread must call interrupt   and cancel   on the thread  I added mmInStream close   and mmOutStream close   in the ConnectedTread cancel   method   After closing the threads streams sockets properly I could create new sockets without any problem

User · Answer

I have also receive the same IOException  but I find the Android system demo   BluetoothChat  project is worked  I determined the problem is the UUID   So i replace my UUID fromString  00001001-0000-1000-8000-00805F9B34FB   to UUID fromString  8ce255c0-200a-11e0-ac64-0800200c9a66   and it worked most scene only sometimes need to restart the Bluetooth device

User · Answer

First  if you need to talk to a bluetooth 2 x device  this documentation states that       Hint  If you are connecting to a Bluetooth serial board then try using   the well-known SPP UUID 00001101-0000-1000-8000-00805F9B34FB  However   if you are connecting to an Android peer then please generate your own   unique UUID    I didn t think that it would work  but only by replacing the UUID with 00001101-0000-1000-8000-00805F9B34FB it works  However  this code seems to handle the problem of SDK version  and you can just replace the function device createRfcommSocketToServiceRecord mMyUuid   with tmp   createBluetoothSocket mmDevice   after defining the following method    private BluetoothSocket createBluetoothSocket BluetoothDevice device      throws IOException       if Build VERSION SDK INT  gt   10           try               final Method m   device getClass   getMethod  createInsecureRfcommSocketToServiceRecord   new Class     UUID class                 return  BluetoothSocket  m invoke device  mMyUuid             catch  Exception e                Log e TAG   Could not create Insecure RFComm Connection  e                       return  device createRfcommSocketToServiceRecord mMyUuid       The source code isn t mine  but comes from this website

User · Answer

You put registerReceiver receiver  new IntentFilter  android bleutooth device action UUID     with  bluetooth  spelled  bleutooth

[android] IOException: read failed, socket might closed - Bluetooth on Android 4.3

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