java之socket的OOBInline和UrgentData和发送心跳包研究

UrgentData可以理解为紧急发送数据方式，如果我们客户端先用write方法写入数据，再用UrgentData发送数据，再去执行flush操作，我们可以得到服务端先打印UrgentData发送的数据，然后再打印write写入的数据。

客户端代码实现：

package com.chenyu.string.cn;import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.Socket;public class ClientTest {public static Socket socket;public static final String LocalHOST = "127.0.0.1";public static final int PORT = 1234;public static void main(String[] args) {Client(LocalHOST, PORT);}public static void Client(String address, int port) {try {socket = new Socket(address, port);} catch (Exception e) {System.out.println("connection reset");return;}if (socket != null && socket.isConnected()) {try {socket.setOOBInline(true);OutputStream out = socket.getOutputStream();OutputStreamWriter outWriter = new OutputStreamWriter(out);outWriter.write(67); // 向服务器发送字符"C"outWriter.write("hello world\r\n");socket.sendUrgentData(65); // 向服务器发送字符"A"socket.sendUrgentData(322); // 向服务器发送字符"B"outWriter.flush();socket.sendUrgentData(214); // 向服务器发送汉字”中”socket.sendUrgentData(208);socket.sendUrgentData(185); // 向服务器发送汉字”国”socket.sendUrgentData(250);socket.close();} catch (Exception e) {System.out.println("has throw exception");e.printStackTrace();} finally {try {if (socket != null) {socket.close();}} catch (IOException e) {System.out.println("socket close fail");}}} else {System.out.println("socket is null or socket connect fail");}}
}

服务端代码实现：

package com.chenyu.string.cn;import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;public class TestInline {public static ServerSocket serverSocket;public static Socket socket;public static void main(String[] args) {try {serverSocket = new ServerSocket(1234);} catch (IOException e1) {System.out.println("serverSocket is fail");return;}System.out.println("服务器已经启动，端口号：1234");while (true) {try {socket = serverSocket.accept();socket.setOOBInline(true);InputStream in = socket.getInputStream();InputStreamReader inReader = new InputStreamReader(in);BufferedReader bReader = new BufferedReader(inReader);String result;while ((result = bReader.readLine()) != null) {System.out.println(result);}
//              char [] cha = new char[1024];
//              int len = inReader.read(cha);
//              System.out.println(new String(cha,0,len));socket.close();} catch (Exception e){System.out.println("read data fail");} finally {if (socket != null) {try {socket.close();} catch (IOException e) {System.out.println("socket close fail");}}}}}
}    socket = serverSocket.accept();socket.setOOBInline(true);InputStream in = socket.getInputStream();InputStreamReader inReader = new InputStreamReader(in);BufferedReader bReader = new BufferedReader(inReader);String result;while ((result = bReader.readLine()) != null) {System.out.println(result);}
//              char [] cha = new char[1024];
//              int len = inReader.read(cha);
//              System.out.println(new String(cha,0,len));socket.close();} catch (Exception e){System.out.println("read data fail");} finally {if (socket != null) {try {socket.close();} catch (IOException e) {System.out.println("socket close fail");}}}}}
}

运行结果（先运行服务端，后运行客户端）：

服务器已经启动，端口号：1234
ABChello world
中国

说明使用sendUrgentData方法发送数据后，系统会立即将这些数据发送出去；而使用write发送数据，必须要使用flush方法才会真正发送数据。

在使用setOOBInline方法打开SO_OOBINLINE选项时要注意是必须在客户端和服务端程序同时使用setOOBInline方法打开这个选项，否则无法命名用sendUrgentData来发送数据。

总结：

我们还可以通过socket.sendUrgentData(0xff);来检测是否与服务端连通，和ping IP 效果差不多，其它的socket.isConnected() socket.isOutputShutdown()都是本地检测，我们上面socket发送数据，如果在安卓客户端，我们可以用这个来发送心跳包，

类似上面客户端的代码，通过后台下发的IP和端口配置，开启线程，out.write(data),通过handler.postDelay(Runable, delayTime)发送心跳包给服务端。