java网络编程Socket中SO_LINGER选项的用法解读

http://blog.sina.com.cn/s/blog_6b1990eb0101171o.html

1：设置该选项: public void setSoLinger(boolean on, int seconds) throws SocketException;

<wbr><wbr><wbr>读取该选项：public int getSoLinger() throws SocketException</wbr></wbr></wbr>

<wbr><wbr><wbr>SO_LINGER选项用来控制Socket关闭时的行为，默认情况下，执行Socket的close方法，该方法会立即返回，但底层的Socket实际上并不会立即关闭，他会立即延迟一段时间，知道发送完剩余的数据，才会真正的关闭Socket，断开连接。</wbr></wbr></wbr>

<wbr><wbr>setSoLinger（true, 0): 执行该方法，那么执行Socket的close方法，该方法也会立即返回，但底层的Socket也会立即关闭，所有未发送完的剩余数据被丢弃</wbr></wbr>

<wbr><wbr>setSoLinger(true, 3600): 那么执行Socket的close方法，该方法不会立即返回，而进入阻塞状态，同时，底层的Socket也会尝试发送剩余的数据，只有满足下面的两个条件之一，close方法才会返回：</wbr></wbr>

<wbr><wbr>（1）：底层的Socket已经发送完所有的剩余数据</wbr></wbr>

<wbr><wbr>（2）： 尽管底层的Socket还没有发送完所有的剩余数据，但已经阻塞了3600秒，close()方法的阻塞时间超过3600秒，也会返回，剩余未发送的数据被丢弃。</wbr></wbr>

<wbr></wbr>

2：类SimpleClient

import java.io.IOException;

import java.io.OutputStream;

import java.net.Socket;

import java.net.UnknownHostException;

public class SimpleClient {

<wbr>public static void main(String[] args) throws UnknownHostException, IOException {</wbr>

<wbr>Socket socket = new Socket("localhost", 8000);</wbr>

<wbr>//socket.setSoLinger(true, 0); <wbr><wbr><wbr><wbr><wbr><wbr>//Socket关闭后，底层Socket立即关闭</wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr>//socket.setSoLinger(true, 3600); <wbr><wbr><wbr><wbr>//Socket关闭后，底层Socket延迟3600秒再关闭</wbr></wbr></wbr></wbr></wbr>

<wbr>OutputStream os = socket.getOutputStream();</wbr>

<wbr>StringBuffer sb = new StringBuffer();</wbr>

<wbr>for(int i = 0; i &lt; 10000; i++) {</wbr>

<wbr><wbr>sb.append(i);</wbr></wbr>

<wbr>}</wbr>

<wbr>os.write(sb.toString().getBytes()); <wbr><wbr><wbr><wbr>//发送一万个字符</wbr></wbr></wbr></wbr></wbr>

<wbr>System.out.println("开始关闭Socket");</wbr>

<wbr>long begin = System.currentTimeMillis();</wbr>

<wbr>socket.close();</wbr>

<wbr>long end = System.currentTimeMillis();</wbr>

<wbr>System.out.println("关闭socket所使用的时间为：" + (end - begin) + "ms");</wbr>

<wbr>}</wbr>

}

<wbr></wbr>

3：类SimpleServer

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.net.ServerSocket;

import java.net.Socket;

public class SimpleServer {

<wbr>public static void main(String[] args) throws IOException, InterruptedException {</wbr>

<wbr><wbr>ServerSocket serverSocket = new ServerSocket(8000);</wbr></wbr>

<wbr><wbr>Socket socket = serverSocket.accept();</wbr></wbr>

<wbr><wbr><wbr></wbr></wbr></wbr>

<wbr><wbr>Thread.sleep(5000); <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>//睡眠5秒钟后再读输入流</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr></wbr></wbr></wbr>

<wbr><wbr>InputStream inputStream = socket.getInputStream();</wbr></wbr>

<wbr><wbr>ByteArrayOutputStream buffer = new ByteArrayOutputStream();</wbr></wbr>

<wbr><wbr>byte[] buff = new byte[1024];</wbr></wbr>

<wbr><wbr>int len = -1;</wbr></wbr>

<wbr><wbr>do {</wbr></wbr>

<wbr><wbr><wbr>len = inputStream.read(buff);</wbr></wbr></wbr>

<wbr><wbr><wbr>System.out.println(len);</wbr></wbr></wbr>

<wbr><wbr><wbr>if(len != -1) {</wbr></wbr></wbr>

<wbr><wbr><wbr>buffer.write(buff, 0, len);</wbr></wbr></wbr>

<wbr><wbr><wbr>}</wbr></wbr></wbr>

<wbr><wbr>} while(len != -1);</wbr></wbr>

<wbr><wbr>System.out.println(new String(buffer.toByteArray())); <wbr><wbr><wbr>//把字节数组转换为字符串</wbr></wbr></wbr></wbr></wbr>

<wbr>}</wbr>

}

<wbr></wbr>

4:测试方法

<wbr><wbr>（1）先启动SimpleServer进程，再启动SimpleClient进程</wbr></wbr>

<wbr><wbr>（2）把 //socket.setSoLinger(true, 0); <wbr><wbr><wbr><wbr><wbr><wbr>//Socket关闭后，底层Socket立即关闭</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr>的注释去掉，再次先后启动SimpleServer和SimpleClient 进程，这样当Socket关闭时，会强行关闭底层的Socket,</wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr>所有未发送完的数据丢失</wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr>（3）把//socket.setSoLinger(true, 3600); <wbr><wbr><wbr><wbr>//Socket关闭后，底层Socket延迟3600秒再关闭</wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr>的注释去掉，再次先后启动SimpleServer和SimpleClient进程，这样当SimpleClient执行Socket的close方法时，</wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr>会进入阻塞状态，直到等待了3600秒，或者底层Socket已经把所有未发送的剩余数据发送完毕，才会从close返回</wbr></wbr></wbr></wbr></wbr></wbr>