Java nio：客户端已断开连接且服务器未被阻止.selector.select（）始终返回1

Question

当我在学习NiO Java时出现了bug。当客户端断开连接时，服务器不会被阻塞.selector.select（）总是返回1

Answer 1

这是有道理的。套接字通道始终可读，read始终返回EOF。

从频道中读取EOF后，您需要将其从选择器中删除。

Answer 2

这是我的代码

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package com.socket.Server;


import java.io.IOException;  
import java.net.InetSocketAddress;  
import java.net.ServerSocket;  
import java.net.Socket;  
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.nio.charset.Charset;  
import java.util.HashMap;  
import java.util.Map;  
import java.util.Set;  
  
public class ImSocketServer {  
    private int port = 8888;  
    private Charset cs = Charset.forName("gbk");  
    private static ByteBuffer sBuffer = ByteBuffer.allocate(1024);  
    private static ByteBuffer rBuffer = ByteBuffer.allocate(1024);  
    private Map<String, SocketChannel> clientsMap = new HashMap<String, SocketChannel>();  
    private static Selector selector;  
      
    public ImSocketServer(int port){  
        this.port = port;  
        try {  
            init();  
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
    }  
    private void init() throws IOException{  

    	ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();  
        serverSocketChannel.configureBlocking(false);  
        ServerSocket serverSocket = serverSocketChannel.socket();  
        serverSocket.bind(new InetSocketAddress(port));  
        selector = Selector.open();  
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        System.out.println("server start on port:"+port);  
    }  

    private void listen(){  
        while (true) {  
            try {   
            	System.out.println(selector.select());  
                Set<SelectionKey> selectionKeys = selector.selectedKeys();  
                for(SelectionKey key : selectionKeys){  
                   
                    try{
                    	 handle(key); 
                        
                        }
                        catch(Exception e){
                        	System.out.println("挂了");
                        }
                }  
                selectionKeys.clear(); 
                selector.selectedKeys().clear();
            } catch (Exception e) {  
                e.printStackTrace();  
                break;  
            }  
              
        }  
    }  
    
    private void handle(SelectionKey selectionKey) throws IOException {  
        ServerSocketChannel server = null;  
        SocketChannel client = null;  
        String receiveText=null;  
        int count=0;  
        if (selectionKey.isAcceptable()) {  
            server = (ServerSocketChannel) selectionKey.channel();  
            client = server.accept();  
            client.configureBlocking(false);  
            client.register(selector, SelectionKey.OP_READ);  
        } else if (selectionKey.isReadable()) {  
            client = (SocketChannel) selectionKey.channel();  
            rBuffer.clear();  
            count = client.read(rBuffer);
            if (count > 0) {  
                rBuffer.flip();  
                receiveText = String.valueOf(cs.decode(rBuffer).array());  
                System.out.println(client.toString()+":"+receiveText);  
                dispatch(client, receiveText);  
                client = (SocketChannel) selectionKey.channel();  
                client.register(selector, SelectionKey.OP_READ);  
            }  
        }   
    }  

    private void dispatch(SocketChannel client,String info) throws IOException{  
        Socket s = client.socket();  
        String name = "["+s.getInetAddress().toString().substring(1)+":"+Integer.toHexString(client.hashCode())+"]";  
        if(!clientsMap.isEmpty()){  
            for(Map.Entry<String, SocketChannel> entry : clientsMap.entrySet()){  
                SocketChannel temp = entry.getValue();  
                if(!client.equals(temp)){  
                    sBuffer.clear();  
                    sBuffer.put((name+":"+info).getBytes());  
                    sBuffer.flip();  
                    temp.write(sBuffer);  
                }  
            }  
        }  
        clientsMap.put(name, client);  
    }  
    public static void main(String[] args) throws IOException {  
        ImSocketServer server = new ImSocketServer(7777);  
        server.listen();  
    }  
} 

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