Проблема с отправкой сообщений с помощью Wifip2p в Android

Question

Я попытался создать приложение, в котором я мог бы передавать сообщения, используя соединение Wifip2p между двумя мобильными телефонами Android. Хотя я могу соединить два мобильных телефона, но я не могу отправлять сообщения с одного мобильного телефона на другой. Приложение закрывается при отправке сообщения. Я знаю, в чем проблема, но я не понимаю, как ее решить? Код приведен ниже:

Это мой файл activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/onOff"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:layout_marginStart="28dp"
        android:layout_marginTop="55dp"
        android:text="Wifi On" />

    <Button
        android:id="@+id/discover"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/onOff"
        android:layout_alignBottom="@+id/onOff"
        android:layout_centerHorizontal="true"
        android:text="discover" />

    <ListView
        android:id="@+id/peerListView"
        android:layout_width="match_parent"
        android:layout_height="200dp"
        android:layout_alignParentStart="true"
        android:layout_below="@+id/onOff"
        android:layout_marginTop="25dp"
        android:background="@android:color/holo_orange_light" />

    <TextView
        android:id="@+id/readMsg"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentEnd="true"
        android:layout_alignParentStart="true"
        android:layout_below="@+id/peerListView"
        android:layout_marginTop="31dp"
        android:text="Message"
        android:textAlignment="center"
        android:textSize="20sp"
        android:textStyle="italic" />

    <EditText
        android:id="@+id/writeMsg"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentStart="true"
        android:ems="10"
        android:inputType="textPersonName"
        android:layout_toStartOf="@+id/sendButton" />

    <Button
        android:id="@+id/sendButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentEnd="true"
        android:text="Send" />

    <TextView
        android:id="@+id/connectionStatus"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:layout_marginTop="15dp"
        android:text="Connection Status"
        android:textAlignment="center"
        android:textColor="@android:color/holo_blue_dark"
        android:textSize="18sp"
        android:textStyle="italic" />

</RelativeLayout> 

Это файл AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.wifip2p.iotwifi">

    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"></uses-permission>
    <uses-permission android:name="android.permission.CHANGE_WIFI_STATE"></uses-permission>
    <uses-permission android:name="android.permission.CHANGE_NETWORK_STATE"></uses-permission>
    <uses-permission android:name="android.permission.INTERNET"></uses-permission>
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"></uses-permission>
    <uses-feature android:name="android.hardware.wifi.direct" android:required="true" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Это файл mainactivity.java

package com.wifip2p.iotwifi;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.IntentFilter;
import android.graphics.Color;
import android.net.wifi.WifiManager;
import android.net.wifi.p2p.WifiP2pConfig;
import android.net.wifi.p2p.WifiP2pDevice;
import android.net.wifi.p2p.WifiP2pDeviceList;
import android.net.wifi.p2p.WifiP2pInfo;
import android.net.wifi.p2p.WifiP2pManager;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;


import com.google.gson.Gson;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    Button btnOnOff,btnDiscover,btnSend;
    ListView listView;
    TextView read_msg_box,connectionStatus;
    EditText writeMsg;
    WifiManager wifiManager;
    WifiP2pManager mManager;
    WifiP2pManager.Channel mChannel;
    BroadcastReceiver mReceiver;
    String[] deviceNameArray;
    WifiP2pDevice[] deviceArray;

    private final IntentFilter mIntentFilter = new IntentFilter();
    private Collection<WifiP2pDevice> peers = new ArrayList<WifiP2pDevice>();


    static final int MESSAGE_READ=1;

    ServerClass serverClass;
    ClientClass clientClass;
    SendReceive sendReceive;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initialWork();
        exqListener();
    }

    Handler handler = new Handler(new Handler.Callback() {
        @Override
        public boolean handleMessage(Message msg) {
            switch (msg.what){
                case MESSAGE_READ:
                    byte[] readBuff = (byte[]) msg.obj;
                    String tempMsg =  new String(readBuff,0,msg.arg1);
                    if(tempMsg != null) {
                        read_msg_box.setText(tempMsg);
                    }
                    break;
            }
            return true;
        }
    });

    private void exqListener() {

        btnOnOff.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(wifiManager.isWifiEnabled()){
                    wifiManager.setWifiEnabled(false);
                    btnOnOff.setText("Off");
                    btnOnOff.setBackgroundColor(Color.GREEN);
                } else {
                    wifiManager.setWifiEnabled(true);
                    btnOnOff.setText("ON");
                    btnOnOff.setBackgroundColor(Color.RED);
                }
            }
        });
        btnDiscover.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mManager.discoverPeers(mChannel, new WifiP2pManager.ActionListener() {
                    @Override
                    public void onSuccess() {
                        connectionStatus.setText("Discovery Started");
                    }

                    @Override
                    public void onFailure(int reason) {
                        connectionStatus.setText("Discovery Failed");
                    }
                });
            }
        });
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                final WifiP2pDevice device = deviceArray[i];
                WifiP2pConfig config = new WifiP2pConfig();
                config.deviceAddress = device.deviceAddress;

                mManager.connect(mChannel, config, new WifiP2pManager.ActionListener() {
                    @Override
                    public void onSuccess() {
                        Toast.makeText(getApplicationContext(),"Connected to "+device.deviceName,Toast.LENGTH_SHORT).show();
                    }

                    @Override
                    public void onFailure(int reason) {
                        Toast.makeText(getApplicationContext(),"Not Connected",Toast.LENGTH_SHORT).show();
                    }
                });

            }
        });
        btnSend.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                String msg = writeMsg.getText().toString();
                if(sendReceive != null) {
                    sendReceive.write(msg.getBytes());
                } else {
                    Toast.makeText(getApplicationContext(),"No SR Obj found",Toast.LENGTH_SHORT).show();
                }
            }
        });
    }

    WifiP2pManager.PeerListListener peerListListener = new WifiP2pManager.PeerListListener() {
        @Override
        public void onPeersAvailable(WifiP2pDeviceList peerList) {
            Collection<WifiP2pDevice> refreshedPeers =  peerList.getDeviceList();

            if(!refreshedPeers.equals(peers)){
                peers.clear();
                peers.addAll(refreshedPeers);
                deviceNameArray = new String[refreshedPeers.size()];
                deviceArray = new WifiP2pDevice[refreshedPeers.size()];
                int index = 0;
                // maybe we can get more information here
                for(WifiP2pDevice device : refreshedPeers){
                    deviceNameArray[index] = device.deviceName;
                    deviceArray[index] = device;
                    index++;
                }
                Log.d("this is my array", "arr: " + Arrays.toString(deviceNameArray));
                ArrayAdapter<String> adapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_list_item_1, deviceNameArray);
                listView.setAdapter(adapter);
            }

            if(peers.size() == 0){
                Toast.makeText(getApplicationContext(),"No Device Found",Toast.LENGTH_SHORT).show();
                Log.d("WIFIDIRECT", "No devices found");
                return;
            }
        }
    };

    WifiP2pManager.ConnectionInfoListener connectionInfoListener= new WifiP2pManager.ConnectionInfoListener() {
        @Override
        public void onConnectionInfoAvailable(WifiP2pInfo wifiP2pInfo) {
            final InetAddress groupOwnerAddress = wifiP2pInfo.groupOwnerAddress;
            if(wifiP2pInfo.groupFormed && wifiP2pInfo.isGroupOwner){
                connectionStatus.setText("Host");
                serverClass = new ServerClass();
                serverClass.start();
            } else if (wifiP2pInfo.groupFormed) {
                connectionStatus.setText("Client");
                clientClass = new ClientClass(groupOwnerAddress);
                clientClass.start();
            }
        }
    };


    public class ServerClass extends Thread{
        Socket socket;
        ServerSocket serverSocket;

        @Override
        public void run() {
            try{
                serverSocket = new ServerSocket(8888);
                socket = serverSocket.accept();
                sendReceive = new SendReceive(socket);
                sendReceive.start();
            }catch (IOException e){
                e.printStackTrace();
            }
        }
    }

    public class ClientClass extends Thread{
        Socket socket;
        String hostAdd;
        public ClientClass(InetAddress hostAddress){
            hostAdd = hostAddress.getHostAddress();
            socket = new Socket();
        }

        @Override
        public void run() {
            try{
                socket.connect(new InetSocketAddress(hostAdd,8888),500);
                sendReceive = new SendReceive(socket);
                sendReceive.start();
            } catch (IOException e){
                e.printStackTrace();
            }
        }
    }

    @Override
    protected void onPause() {
        super.onPause();
        unregisterReceiver(mReceiver);
    }

    @Override
    protected void onResume() {
        super.onResume();
        registerReceiver(mReceiver,mIntentFilter);
    }

    private class SendReceive extends Thread{
        private Socket socket;
        private InputStream inputStream ;
        private OutputStream outputStream;

        private SendReceive(Socket skt){
            socket = skt;
            try{
                inputStream = socket.getInputStream();
                outputStream = socket.getOutputStream();
            }catch(IOException e){
                e.printStackTrace();
            }
        }

        @Override
        public void run() {
            byte[] buffer = new byte[1024];
            int bytes;
            while(socket != null){
                try {
                    bytes= inputStream.read(buffer);
                    if(bytes>0){
                        handler.obtainMessage(MESSAGE_READ,bytes,-1,buffer).sendToTarget();
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

        private void write (byte[] bytes){
            if(bytes != null) {
                try {
                    outputStream.write(bytes);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    private void initialWork() {
        btnOnOff =  findViewById(R.id.onOff);
        btnDiscover =  findViewById(R.id.discover);
        btnSend =  findViewById(R.id.sendButton);
        listView =  findViewById(R.id.peerListView);
        read_msg_box =  findViewById(R.id.readMsg);
        connectionStatus =  findViewById(R.id.connectionStatus);
        writeMsg =  findViewById(R.id.writeMsg);

        mIntentFilter.addAction(WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION);
        mIntentFilter.addAction(WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION);
        mIntentFilter.addAction(WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION);
        mIntentFilter.addAction(WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION);

        wifiManager = (WifiManager) getApplicationContext().getSystemService(Context.WIFI_SERVICE);
        mManager = (WifiP2pManager) getSystemService(Context.WIFI_P2P_SERVICE);
        mChannel = mManager.initialize(this,getMainLooper(),null);
        mReceiver = new WifiDirectBroadcastReceiver(mManager,mChannel,this);
    }
}

А это мой файл WifiDirectBroadcastReceiver.java

package com.wifip2p.iotwifi;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.net.NetworkInfo;
import android.net.wifi.p2p.WifiP2pManager;
import android.util.Log;
import android.widget.Toast;

public class WifiDirectBroadcastReceiver extends BroadcastReceiver {

    private WifiP2pManager mManager;
    private WifiP2pManager.Channel mChannel;
    private MainActivity mActivity;

    public WifiDirectBroadcastReceiver(WifiP2pManager mManager,WifiP2pManager.Channel mChannel,MainActivity mActivity){
        this.mManager = mManager;
        this.mChannel = mChannel;
        this.mActivity = mActivity;
    }

    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        if (WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION.equals(action)) {
            // Determine if Wifi P2P mode is enabled or not, alert
            // the Activity.
            int state = intent.getIntExtra(WifiP2pManager.EXTRA_WIFI_STATE, -1);
            if (state == WifiP2pManager.WIFI_P2P_STATE_ENABLED) {
                Toast.makeText(context,"WIFI is ON",Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(context,"WIFI is OFF",Toast.LENGTH_SHORT).show();
            }
        } else if (WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION.equals(action)) {

            if(mManager != null){
                mManager.requestPeers(mChannel,mActivity.peerListListener);
            }

        } else if (WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION.equals(action)) {

            if(mManager != null){
                return;
            }
            NetworkInfo networkInfo = intent.getParcelableExtra(WifiP2pManager.EXTRA_NETWORK_INFO);
            if(networkInfo.isConnected()){
                mManager.requestConnectionInfo(mChannel,mActivity.connectionInfoListener);
            } else {
                mActivity.connectionStatus.setText("Device Disconnected");
            }

        } else if (WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION.equals(action)) {

        }
    }

}

Ошибка лежит здесь в файле mainactivity.java

 if(sendReceive != null) {
                    sendReceive.write(msg.getBytes());
                } else {
                    Toast.makeText(getApplicationContext(),"No SR Obj found",Toast.LENGTH_SHORT).show();
                }

sendReceive не создается.