Socket（套接字）是一种通信机制，可以实现单机或跨网络进行通信，其创建需要明确的区分C（客户端）/S（服务器端），支持多个客户端连接到同一个服务器。有两种传输模式：
1）、面向连接的传输：基于TCP协议，可靠性高，但效率低；
2）、面向无连接的传输：基于UDP协议，可靠性低，但效率高；
Android中，直接采用Socket通信应该是我们遇到的最低级的网络运用。尽管已经作了很大程度的抽象，但是纯粹的Socket通信，仍然给开发者留下很多细节需要处理，尤其在服务器端，开发者需要处理多线程以及数据缓冲等的设计问题。相对而言，处于更高抽象层的HTTP等，已经对Socket通信中需要处理的技术细节进行了很好的封装，开发者无须关心，因此，HTTP在网络开发中通常具有决定性的优势。
Android在其核心库的java包中，提供了用于客户端的Socket class和用于服务器端的ServerSocket class，分别位于$SOURCE/libcore/luni/src/main/java/java/net/Socket.java和$SOURCE/libcore/luni/src/main/java/java/net/ServerSocket.java文件中。分析两个class的源码，可以看出封装考虑的很全面，只构造方法一向每个class都考虑了很多种使用情况。由于本人只是初学者，很多理解的不深入，这里只抛砖引玉的对两个class的构造方法分别介绍一种，就是我下面的程序中用到的：
Socket(String dstName, int dstPort)：创建一个以流的方式（基于TCP协议）连接到目标机（这里可以理解为服务器）的客户端Socket；dstName是目标机的IP地址，dstPort是要连接的目标机的端 口号。这里要注意对端口的理解，它不能理解为物理上的一个接口，而是对计算机中一块特殊内存区域的形象表述。
ServerSocket(int aport)：创建一个绑定到本机指定端口的服务端Socket；aport就是指定的本机端口。与上述客户端Socket对应，通过TCP连接时，ServerSocket创建后需要在aport端口上进行监听，等待客户端的连接。
启动 service 和 activity
mContext.startService(new Intent(mContext, SocketService.class));
Intent intent = new Intent();
intent.setClass(mContext, SocketClientDemo.class);
mContext.startActivity(intent);
service ：服务端
package com.android.settings;
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.net.ServerSocket;
import java.net.Socket;
import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
public class SocketService extends Service {
Thread mServiceThread;
Socket client;
@Override
public IBinder onBind(Intent intent) {
// TODO Auto-generated method stub
return null;
}
@Override
public void onCreate() {
// TODO Auto-generated method stub
super.onCreate();
mServiceThread = new Thread(new SocketServerThread());
}
@Override
public void onStart(Intent intent, int startId) {
// TODO Auto-generated method stub
super.onStart(intent, startId);
mServiceThread.start();
}
@Override
public void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
}
public class SocketServerThread extends Thread {
private static final int PORT = 54321;
private SocketServerThread() {
}
@Override
public void run() {
try {
ServerSocket server = new ServerSocket(PORT);
while (true) {
System.out.println("tian begin client connected");
client = server.accept();
System.out.println(" tian client connected");
BufferedReader reader = new BufferedReader(
new InputStreamReader(client.getInputStream()));
System.out.println(" tian read from client:");
String textLine = reader.readLine();
if (textLine.equalsIgnoreCase("EXIT")) {
System.out
.println(" tian EXIT invoked, closing client");
break;
}
System.out.println(textLine);
PrintWriter writer = new PrintWriter(new BufferedWriter(
new OutputStreamWriter(client.getOutputStream())));
System.out.println(" return tian read from client:"
+ textLine);
writer.println(" tian ECHO from server: " + textLine);
writer.flush();
writer.close();
reader.close();
}
} catch (IOException e) {
// TODO Auto-generated catch block
System.err.println(e);
}
}
}
}
package com.android.settings;
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.net.Socket;
import java.net.UnknownHostException;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class SocketClientDemo extends Activity {
private static final String SERVERIP = "127.0.0.1";
private static final int SERVERPORT = 54321;
private static final String TAG = "SocketClientDemo";
TextView mMsgRev;
EditText mMsgEdit;
Button mMsgSendBtn;
String mSendMsg;
String mReceivedMsg;
class MyThread implements Runnable {
private String name;
public MyThread(String name) {
this.name = name;
}
public void run() {
// for (int i = 0; i < 100; i++) {
// System.out.println("线程开始：" + this.name + ",i=" + i);
Log.d(TAG, "MyThread execu");
// }
}
};
class MyThread2 extends Thread {
@Override
public void run() {
// TODO Auto-generated method stub
Log.d(TAG, "MyThread2 execu");
}
};
class MyThread3 extends Thread {
private String name;
public MyThread3(String name) {
// super();
this.name = name;
}
@Override
public void run() {
// TODO Auto-generated method stub
Log.d(TAG, "MyThread3 execu" + "name=" + name);
Socket socket = null;
mSendMsg = mMsgEdit.getText().toString();
try {
socket = new Socket(SERVERIP, SERVERPORT);
PrintWriter writer = new PrintWriter(new BufferedWriter(
new OutputStreamWriter(socket.getOutputStream())));
writer.println(mSendMsg);
writer.flush();
BufferedReader reader = new BufferedReader(
new InputStreamReader(socket.getInputStream()));
mReceivedMsg = reader.readLine();
Message meaage = mHander.obtainMessage();
meaage.arg1 = 1;
mHander.sendMessage(meaage);
writer.close();
reader.close();
socket.close();
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.xml.beidou_detail_preference_settings);
mMsgRev = (TextView) findViewById(R.id.receive_msg);
mMsgEdit = (EditText) findViewById(R.id.edit_msg);
mMsgSendBtn = (Button) findViewById(R.id.send_msg);
mMsgSendBtn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
/*
* MyThread thread = new MyThread("00"); new
* Thread(thread).start();
*
* new MyThread2().start();
*/
MyThread3 thread3 = new MyThread3("33");
thread3.start();
}
});
}
final Handler mHander = new Handler() {
@Override
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
if (mReceivedMsg != null) {
mMsgRev.setText(mReceivedMsg);
} else {
mMsgRev.setText("tian receive data error");
}
super.handleMessage(msg);
}
};
}
activity : 客户端
package com.android.settings;
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.net.Socket;
import java.net.UnknownHostException;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class SocketClientDemo extends Activity {
private static final String SERVERIP = "127.0.0.1";
private static final int SERVERPORT = 54321;
private static final String TAG = "SocketClientDemo";
TextView mMsgRev;
EditText mMsgEdit;
Button mMsgSendBtn;
String mSendMsg;
String mReceivedMsg;
class MyThread implements Runnable {
private String name;
public MyThread(String name) {
this.name = name;
}
public void run() {
// for (int i = 0; i < 100; i++) {
// System.out.println("线程开始：" + this.name + ",i=" + i);
Log.d(TAG, "MyThread execu");
// }
}
};
class MyThread2 extends Thread {
@Override
public void run() {
// TODO Auto-generated method stub
Log.d(TAG, "MyThread2 execu");
}
};
class MyThread3 extends Thread {
private String name;
public MyThread3(String name) {
// super();
this.name = name;
}
@Override
public void run() {
// TODO Auto-generated method stub
Log.d(TAG, "MyThread3 execu" + "name=" + name);
Socket socket = null;
mSendMsg = mMsgEdit.getText().toString();
try {
socket = new Socket(SERVERIP, SERVERPORT);
PrintWriter writer = new PrintWriter(new BufferedWriter(
new OutputStreamWriter(socket.getOutputStream())));
writer.println(mSendMsg);
writer.flush();
BufferedReader reader = new BufferedReader(
new InputStreamReader(socket.getInputStream()));
mReceivedMsg = reader.readLine();
Message meaage = mHander.obtainMessage();
meaage.arg1 = 1;
mHander.sendMessage(meaage);
writer.close();
reader.close();
socket.close();
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.xml.beidou_detail_preference_settings);
mMsgRev = (TextView) findViewById(R.id.receive_msg);
mMsgEdit = (EditText) findViewById(R.id.edit_msg);
mMsgSendBtn = (Button) findViewById(R.id.send_msg);
mMsgSendBtn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
/*
* MyThread thread = new MyThread("00"); new
* Thread(thread).start();
*
* new MyThread2().start();
*/
MyThread3 thread3 = new MyThread3("33");
thread3.start();
}
});
}
final Handler mHander = new Handler() {
@Override
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
if (mReceivedMsg != null) {
mMsgRev.setText(mReceivedMsg);
} else {
mMsgRev.setText("tian receive data error");
}
super.handleMessage(msg);
}
};
}