如此代码，服务器端读取客户端信息时，如果客户端正常关闭，出现循环读问题，CPU被占满。
package com.timerty.select;
import java.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
/**
* Created by zhubo on 2018/1/16.
*/
public class NIOServer {
private Selector selector;
public void initServer(int port) throws Exception{
//获得一个ServerSocket通道
ServerSocketChannel serverChannel = ServerSocketChannel.open();
//设置通道为非阻塞
// 该通道对于serverSocket绑定到port端口
serverChannel.socket().bind(new InetSocketAddress(port));
// 获得一选择器
this.selector = Selector.open();
//将通道管理器和该通道绑定，并未该通道注册selectionKey.OP_ACCEPT事件
//注册该事件后，当事件到达的时候，selector.select()会返回，
// 如果事件没有到达selector.select()会一直阻塞
}
public void listen() throws Exception{
System.out.println("start server ...");
// 轮训访问seletor
while(true){
//当注册事件到达时，方法返回，否则该方法会一直阻塞
selector.select();
// 获得selector中选中项的地带器，选中项为注册事件
Iterator iterator = this.selector.selectedKeys().iterator();
if(iterator.hasNext()){
SelectionKey key = ();
//删除已选的key 以防止重复处理
//客户端请求链接事件
if(key.isValid() && key.isAcceptable()){
System.out.println(&#");
ServerSocketChannel server = (ServerSocketChannel) key.channel();
//获取客户端链接的通道
SocketChannel channel = server.accept();
// 非阻塞模式
//channel.write(ByteBuffer.wrap(new String("Hello Client").getBytes()));
// 在客户端链接成功后，为了可以连接到客户端的信息，需要给通道设置读的权限
}else if(key.isValid() && key.isReadable()){
read(key);
}
}
}
}
private void read(SelectionKey key) throws Exception {
SocketChannel channel = (SocketChannel)key.channel();
ByteBuffer buffer = ByteBuffer.allocate(100);
byte[] data = buffer.array();
String msg = new String(data).trim();
System.out.println("server receive from client : "+msg);
ByteBuffer outBuffer = ByteBuffer.Bytes());
channel.write(outBuffer);
//key.cancel();
//channel.close();
}
public static void main(String[] args) throws Exception{
NIOServer server = new NIOServer();
server.initServer(8989);
server.listen();
}
}
[root@centos1 ~]# telnet 192.168.1.114 8989
Trying 192.168.
Connected to 192.168.1.114.
Escape character is '^]'.
^]
telnet> send ao
锟斤拷
kdf
kdfdd
ddquit
quit^]
telnet> quit
Connection closed.
[root@centos1 ~]# telnet 192.168.1.114 8989
Trying 192.168.
Connected to 192.168.1.114.
Escape character is '^]'.
^]
telnet> send ao
锟斤拷
abc
abcdd
dd^]
telnet> quit
Connection closed.
[root@centos1 ~]#
当我们telnet切断客户端链接时，会一直出发SocketChannel读就绪事件。会出现循环度问题。
需要我们手动对读取通道数据代码进行改写：
private void read(SelectionKey key) throws Exception {
SocketChannel channel = (SocketChannel)key.channel();
ByteBuffer buffer = ByteBuffer.allocate(100);
try{
int read = ad(buffer);
if(read > 0){
byte[] data = buffer.array();
String msg = new String(data).trim();
System.out.println("server receive from client : "+msg);
ByteBuffer outBuffer = ByteBuffer.Bytes());
channel.write(outBuffer);
}else if(read < 0){
System.out.println("channel closed");
channel.close();
key.cancel();
}else
;
}catch (Exception e){
System.out.println("channel exception closed");
channel.close();
key.cancel();
}
//key.cancel();
//channel.close();
}
这样不管，客户端异常关闭导致的服务器异常退出，还是 客户端正常关闭导致的循环读问题都不会出现
本文发布于:2024-02-02 08:11:11，感谢您对本站的认可！
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