java - Android socket原理及异常

Question

我是 android 中 java 套接字的初学者。我遇到了一些问题，需要帮助来解决这些问题。

我使用底部代码连接到服务器 Socket，一切正常。但是当调用 disconnect 方法并尝试再次连接时，我遇到了 socket is null 或 BufferedReader 对象在断开连接并再次连接后总是返回 null 的问题。也许我的断开方式是错误的。在某些时候断开套接字的最佳方法是什么，例如中断互联网并再次连接？

这是我连接和断开套接字的代码。

public class HelperSocket {

public static Socket socket = null;
public static DataOutputStream writer = null;
public static BufferedReader reader = null;
public static DataInputStream inputStream = null;
public static final String SOCKET_ADDRESS = "aUrlForSocket";
public static final int SOCKET_PORT = 6000;
public static final int SOCKET_TIMEOUT = 30000;
public static Thread clientThread;
public static boolean isConnected = false;

public static boolean connect() {
    Utils.Log("StartConnect");
    if (!isConnected) {
        clientThread = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    InetAddress address = InetAddress.getByName(HelperSocket.SOCKET_ADDRESS);
                     socket = new Socket(address.getHostAddress(), SOCKET_PORT);

                    isConnected = true;
                    socket.setSoTimeout(SOCKET_TIMEOUT);

                    writer = new DataOutputStream(socket.getOutputStream());
                    reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                    inputStream = new DataInputStream(socket.getInputStream());

                    while (HelperSocket.isConnected) {
                        Utils.Log("onWhile" + reader.hashCode());
                        try {

                            if (reader.readLine() != null) {
                                Utils.Log(reader.readLine() + "");
                            } else {
                                Utils.Log("getNullFromServer");
                                //data get null here :)
                                disconnect();
                            }
                        } catch (IOException e) {
                            Utils.Log("ProblemOnReadData" + e.getMessage());
                            e.printStackTrace();
                        }
                    }
                } catch (IOException e) {
                    Utils.Log("SocketProblemAt connect:" + e.getMessage());
                    e.printStackTrace();
                }
            }
        });
        clientThread.start();
    }

    return true;
}

public static boolean disconnect() {
    isConnected = false;
    if (!clientThread.isInterrupted())
        clientThread.interrupt();
    if (socket != null) {
        Utils.Log("SocketAndAllObjectCleared");
        try {
            socket.shutdownInput();
            socket.shutdownOutput();
            socket = null;
        } catch (IOException e) {
            e.printStackTrace();
        }

       /* stream = null;
        reader = null;*/
    }
    return false;
}


}

我在网络连接变化时创建了一个接收器，并且需要在设备未连接到互联网时断开套接字，并在建立互联网连接后重新连接。

接收者:

public class BroadcastChangeNet extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        if (Utils.isNetworkConnected()) {
            HelperSocket.connect();
            Utils.Log("NetWorkConnect");
        } else {
            HelperSocket.disconnect();
            Utils.Log("NetWorkDisConnect");
        }
    }
}

检查网络情况:

 public static boolean isNetworkConnected() {
        ConnectivityManager conMgr =
                (ConnectivityManager) ApplicationClass.context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo i = conMgr.getActiveNetworkInfo();
        if (i == null)
            return false;
        if (!i.isConnected())
            return false;
        if (!i.isAvailable())
            return false;
        return true;
    }

Answer 1

从我的角度来看，您只需要创建合适的 Jave 类，下面是我测试成功的代码，

import android.content.Context;

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.Socket;
import java.net.SocketException;
import java.net.UnknownHostException;

/**
 * Created by Kintan Patel on 01-08-2016.
 */
public class SocketConnection {
    private Socket socket = null;
    private OutputStream outputStream;
    private DataOutputStream dataOutputStream;
    private SessionHelper helper;

    public String EstablishConnection(String token) {
   // token = your message that write on socket server
        String response;
        try {

            //socket = new Socket("192.168.0.24", 2129); // Testing Server
            socket = new Socket("Your IpAddress", PORT NO); 
            outputStream = socket.getOutputStream();
            dataOutputStream = new DataOutputStream(outputStream);
            dataOutputStream.writeUTF(token);
            BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            response = br.readLine();

        } catch (UnknownHostException e) {
            e.printStackTrace();
            response = "UnknownHostException: " + e.toString();
            return null;

        } catch (SocketException e) {
            e.printStackTrace();
            response = "Sorry Fail to connect";
            return null;

        } catch (IOException e) {
            // TODO Auto-generated catch block
            // e.printStackTrace();

            response = "Sorry Fail to connect";
            return null;

        } catch (Exception e) {
            e.printStackTrace();
            response = "Server Break";
            return null;

        } finally {
            if (socket != null) {
                try {
                    socket.close();
                    outputStream.close();
                    dataOutputStream.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
        return response;
    }
}

现在从您的主类简单地创建 SocketConnection 类的对象并使用 EstablishConnection() 方法，

eg :

     SocketConnection connection = new SocketConnection();
         String token = "message that you want to write on server";
         String response = connecation.EstablishConnection(token);

如果你想使用 AsynkTask，下面是 AsynkTask 代码:

private class ActivationTask extends AsyncTask<String, String, String> {

        @Override
        protected String doInBackground(String... params) {
            SocketConnection connection = new SocketConnection();
            String token = "getActivation|" + params[0] + "|";
            return connection.EstablishConnection(token);
        }


        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            progressDialog.show();
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            progressDialog.dismiss();
            if (s != null) {
                 Log.e("RESULT" , s);



            }
        }
    }