Android进程间通信(IPC)之Socket

Socket也被称为“套接字”编程，它分为流式套接字和用户数据套接字两种，分别对应于网络传输控制中层中TCP和UDP协议。TCP协议是面向连接的协议，提供稳定的双向通信功能，TCP连接的建立需要经过”三次握手”才能实现，为了实现稳定的数据传输功能，其本身提供了超时重传机制，具有很高的稳定性。UDP是无连接的，提供不稳定的单向通信功能,当然UDP也可以实现双向通信功能，在性能上，UDP就有更好的效率，其缺点是不能保证数据一定传输正确，尤其是网络拥塞的情况下。
演示一个Socket聊天的程序：

服务端

package com.app.service;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Random;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;

public class TcpService extends Service {
private boolean mIsServiceDestoryed = false;
private String[] mDefinedMessage = new String[] { "你好", "hello", "辛苦了" };
private ServerSocket mServerSocket;

@Override
public IBinder onBind(Intent intent) {
return null;
    }

@Override
public void onCreate() {
super.onCreate();
new Thread(new TcpThread()).start();
    }

    class TcpThread implements Runnable {

@Override
public void run() {
try {
//服务端在8688这个端口监听
                mServerSocket = new ServerSocket(8688);
            } catch (IOException e) {
                e.printStackTrace();
return;
            }

while (!mIsServiceDestoryed) {
try {
//一个阻塞的方法，当有客户端Socket时会运行
final Socket socket = mServerSocket.accept();
new Thread() {
@Override
public void run() {
                            responseClient(socket);
                        }
                    }.start();
                } catch (IOException e) {
                    e.printStackTrace();
                }

            }

        }

    }
//服务端相应客户端
private void responseClient(Socket socket) {
try {
//读取客户端发来的消息
            BufferedReader in = new BufferedReader(new InputStreamReader(
                    socket.getInputStream()));
//用于向客户端发送消息
            PrintWriter out = new PrintWriter(new BufferedWriter(
new OutputStreamWriter(socket.getOutputStream())), true);
            out.println("欢迎来到聊天室!");
while (!mIsServiceDestoryed) {
                String str = in.readLine();//通信连接后,客户端不发消息，这个方法会一直阻塞
                Log.e("tag", "客户端消息：====" + str);
if (str == null) {
break;
                }
int i = new Random().nextInt(mDefinedMessage.length);
                String msg = mDefinedMessage[i];
                out.println(msg);//向客户端发送消息
            }
//客户端连接断开后，要关闭数据流
            in.close();
            out.close();
            socket.close();
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

@Override
public void onDestroy() {
        mIsServiceDestoryed = true;//停止线程
super.onDestroy();
    }
}

客户端
先看布局代码：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#fff"
android:orientation="vertical" >

<EditText
 android:id="@+id/et_recore"
android:layout_width="fill_parent"
android:layout_height="200dip"
android:gravity="top|left"
android:text="聊天记录：\n" >
</EditText>

<EditText
 android:id="@+id/et_send_content"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="输入要发送的内容" >
</EditText>

<Button
 android:id="@+id/btn_send"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="发送"
android:textColor="#000" />

</LinearLayout>

java代码：

package com.app.client;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.net.Socket;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.os.SystemClock;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends Activity implements OnClickListener {
private static final int MESSAGE_RECEIVE_NEW_MSG = 1;
private static final int MESSAGE_SOCKET_CONNECTED = 2;
private Button mButton_Send;
private EditText mEditText01, mEditText02;
private PrintWriter mPintWriter;
private Socket mClientSocket;

private Handler mHandler = new Handler() {

@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case MESSAGE_RECEIVE_NEW_MSG:
                mEditText01.setText(mEditText01.getText() + (String) msg.obj);
break;
case MESSAGE_SOCKET_CONNECTED:
                mButton_Send.setEnabled(true);
                mEditText02.setEnabled(true);
break;

default:
break;
            }
        }
    };

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mButton_Send = (Button) findViewById(R.id.btn_send);
        mEditText01 = (EditText) findViewById(R.id.et_recore);
        mEditText02 = (EditText) findViewById(R.id.et_send_content);
        mButton_Send.setEnabled(false);
        mButton_Send.setOnClickListener(this);
//开启服务
        Intent i = new Intent("com.app.service");
        startService(i);
new Thread() {
@Override
public void run() {
                connectTCPServer();
            }
        }.start();
    }

protected void connectTCPServer() {
        Socket socket = null;
//while里面使用了超时重连策略
while (socket == null) {
try {
                socket = new Socket("localhost", 8688);
                mClientSocket = socket;
                mPintWriter = new PrintWriter(new BufferedWriter(
new OutputStreamWriter(socket.getOutputStream())), true);
                mHandler.sendEmptyMessage(MESSAGE_SOCKET_CONNECTED);
            } catch (Exception e) {
                SystemClock.sleep(1000);
            }
        }
try {
//用于读取服务端的消息
            BufferedReader br = new BufferedReader(new InputStreamReader(
                    mClientSocket.getInputStream(), "utf-8"));
while (!MainActivity.this.isFinishing()) {
                String msg = br.readLine();//读取
                Log.e("tag", "服务端消息：====" + msg);
if (msg != null) {
                    String showeMsg = "server : " + msg + "\n";
                    mHandler.obtainMessage(MESSAGE_RECEIVE_NEW_MSG, showeMsg)
                            .sendToTarget();
                }
            }
//关闭资源
            mPintWriter.close();
            br.close();
            socket.close();
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

@Override
public void onClick(View v) {
        String msg = mEditText02.getText().toString();
if (!TextUtils.isEmpty(msg) && mPintWriter != null) {
            mPintWriter.println(msg);
            mEditText02.setText("");
            String showMsg = "client : " + msg + "\n";
            mEditText01.setText(mEditText01.getText() + showMsg);
        }
    }

@Override
protected void onDestroy() {
if (mClientSocket != null) {
try {
                mClientSocket.shutdownInput();
                mClientSocket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
super.onDestroy();
    }
}

客户端和服务端联网需要权限：

  <uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />