Android客户端使用socket通信

1. 注意
2. 代码

Android作为客户端（client）对服务器（server）进行request操作，并从服务器中得到response。

这里主要使用socket来进行数据传输。

注意

• 若SDK version > 9，则需要加入

  if (android.os.Build.VERSION.SDK_INT > 9) {
      StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
      StrictMode.setThreadPolicy(policy);
  }

  否则会有Error: SocketException: socket failed: EACCES (Permission denied).

• socket的相关操作不能放在UI线程中，否则会有Error: android.os.NetworkOnMainThreadException

代码

在activity_main.xml中加了一个用于用户输入消息的editText，一个发送消息的button，一个显示接收消息的textView。

发送与接收数据可以是string，也可以是object。

若是object的话记得类要implements java.io.Serializable。

• MainActivity.java

  import android.app.Activity;
  import android.os.Bundle;
  import android.os.Handler;
  import android.os.Message;
  import android.os.StrictMode;
  import android.view.View;
  import android.view.View.OnClickListener;
  import android.widget.EditText;
  import android.widget.TextView;
  
  import java.io.BufferedReader;
  import java.io.BufferedWriter;
  import java.io.InputStreamReader;
  import java.io.ObjectInputStream;
  import java.io.ObjectOutputStream;
  import java.io.OutputStreamWriter;
  import java.io.PrintWriter;
  import java.lang.ref.WeakReference;
  import java.net.InetAddress;
  import java.net.Socket;
  import java.util.ArrayList;
  
  public class MainActivity extends Activity {
      public static final String HOST = "10.0.2.2";
      public static final int PORT = 12345;
      public final MyHandler mHandler = new MyHandler(this);
      public EditText mEditText = null;
      public TextView mTextView = null;
  
      @Override
      public void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
          if (android.os.Build.VERSION.SDK_INT > 9) {
              StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
              StrictMode.setThreadPolicy(policy);
          }
          mEditText = (EditText) findViewById(R.id.editText);
          mTextView = (TextView) findViewById(R.id.textView);
          findViewById(R.id.button).setOnClickListener(new OnClickListener() {
              public void onClick(View v) {
                  Message message = mHandler.obtainMessage();
                  message.what = 1;
                  mHandler.sendMessage(message);
              }
          });
      }
  
      public static class MyHandler extends Handler {
          private final WeakReference<MainActivity> mActivity;
  
          public MyHandler(MainActivity activity) {
              mActivity = new WeakReference<>(activity);
          }
  
          public void sendString(MainActivity activity) {
              Socket socket = null;
              try {
                  socket = new Socket(InetAddress.getByName(HOST), PORT);
                  // send message
                  String request = activity.mEditText.getText().toString() + "\n";
                  PrintWriter out = new PrintWriter(new BufferedWriter(
                          new OutputStreamWriter(socket.getOutputStream())),
                          true);
                  out.write(request);
                  out.flush();
  
                  // receive message
                  BufferedReader in = new BufferedReader(
                          new InputStreamReader(socket.getInputStream()));
                  String response = in.readLine();
                  activity.mTextView.setText(response);
  
                  out.close();
                  in.close();
              } catch (Exception e) {
                  e.printStackTrace();
              }
              try {
                  if (socket != null) {
                      socket.close();
                  }
              } catch (Exception e) {
                  e.printStackTrace();
              }
          }
  
          public void sendObject(MainActivity activity) {
              Socket socket = null;
              try {
                  socket = new Socket(InetAddress.getByName(HOST), PORT);
                  // send object
                  ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream());
                  ArrayList<Point> points = new ArrayList<>();
                  points.add(new Point(-3, 3.14));
                  out.writeObject(points);
                  out.flush();
  
                  // receive object
                  ObjectInputStream in = new ObjectInputStream(socket.getInputStream());
                  Object obj = in.readObject();
                  points = (ArrayList<Point>) obj;
                  activity.mTextView.setText(points.toString());
  
                  out.close();
                  in.close();
              } catch (Exception e) {
                  e.printStackTrace();
              }
              try {
                  if (socket != null) {
                      socket.close();
                  }
              } catch (Exception e) {
                  e.printStackTrace();
              }
          }
  
          public void handleMessage(Message msg) {
              MainActivity activity = mActivity.get();
              if (activity != null) {
                  switch (msg.what) {
                      case 0:
                          sendString(activity);
                          break;
                      case 1:
                          sendObject(activity);
                          break;
                  }
              }
          }
      }
  }

• Point.java

  public class Point implements java.io.Serializable {
      public double x, y;
  
      public Point(double x, double y) {
          this.x = x;
          this.y = y;
      }
  }