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

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。