java套接字聊天代码抛出java.net.SocketException：套接字关闭

Question

我尝试用Java套接字API制作基本的Java聊天应用程序。但是当客户端终止时，它会引发以下异常，

socketException：套接字关闭

package com.aaa.server;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class JavaChatServer {

    final static int Port = 10001; 

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        ServerSocket serverSocket = null;
        Map<String, PrintWriter> clientMap = null;

        try {
            serverSocket = new ServerSocket(Port);
            clientMap = new HashMap<String, PrintWriter>();
            Collections.synchronizedMap(clientMap);

            while(true) {
                System.out.println("Waiting Connection ....");
                Socket socket = serverSocket.accept();

                ServerThread thread = new ServerThread(socket, clientMap);
                thread.start();
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if(!serverSocket.isClosed()) {
                    serverSocket.close();
                }
            } catch (Exception e1) {
                e1.printStackTrace();
            }
        }
    }

}

class ServerThread extends Thread {
    private Socket socket = null;
    private BufferedReader br = null;

    private Map<String, PrintWriter> clientMap;
    private String id;

    public ServerThread(Socket socket, Map<String, PrintWriter> clientMap) {
        this.socket = socket;
        this.clientMap = clientMap;
    }

    @Override
    public void run() {
        try {
            br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            PrintWriter pw = new PrintWriter(new OutputStreamWriter(socket.getOutputStream()));

            id = br.readLine();
            broadcast(id + " is connected");
            System.out.println("Connected User Id : " + id);
            clientMap.put(id, pw);

            String msg = "";

            while(true) {
                msg = br.readLine();

                if(msg.equals("/exit")) {
                    break;
                }

                broadcast(id + " : " + msg);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                clientMap.remove(id);
                broadcast(id + " is disconnected!!");

                if (br != null)
                    br.close();
                if(socket != null)
                    socket.close();
            } catch (Exception e1) {
                e1.printStackTrace();
            }
        }
    }

    private void broadcast(String msg) throws Exception{
        Collection<PrintWriter> collection = clientMap.values();
        Iterator<PrintWriter> iterator = collection.iterator();

        while(iterator.hasNext()) {
            PrintWriter pw = iterator.next();
            pw.println(msg);
            pw.flush();
        }
    }
}

package com.aaa.client;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.Scanner;

public class JavaChatClient {

    final static int Port = 10001;

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Socket socket = null;
        PrintWriter pw = null;

        Scanner keyboard = new Scanner(System.in);
        String id = "";

        try {
            socket = new Socket("localhost", Port);

            pw = new PrintWriter(new OutputStreamWriter(socket.getOutputStream()));
            System.out.print("Welcome to Chat Room. Pls, type your ID : ");
            id = keyboard.nextLine();
            pw.println(id);
            pw.flush();

            ClientInputThread inputThread = new ClientInputThread(socket);
            inputThread.start();

            String msg = "";
            while (!msg.toLowerCase().equals("/exit")) {
                msg = keyboard.nextLine();

                if(!msg.trim().equals("")) {
                    pw.println(msg);
                    pw.flush();
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (keyboard != null)
                    keyboard.close();
                if (pw != null)
                    pw.close();
                if(socket != null)
                    socket.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

}

class ClientInputThread extends Thread {
    private Socket socket = null;

    public ClientInputThread (Socket socket) {
        this.socket = socket;
    }

    @Override
    public void run() {
        BufferedReader br = null;

        try {
            br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            String msg = "";

            while(true) {
                if(socket.isClosed())
                    break;

                msg = br.readLine(); // This line throws SocketException
                System.out.println(msg);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

java.net.SocketException: Socket closed
        at java.net.SocketInputStream.read(Unknown Source)
        at java.net.SocketInputStream.read(Unknown Source)
        at sun.nio.cs.StreamDecoder.readBytes(Unknown Source)
        at sun.nio.cs.StreamDecoder.implRead(Unknown Source)
        at sun.nio.cs.StreamDecoder.read(Unknown Source)
        at java.io.InputStreamReader.read(Unknown Source)
        at java.io.BufferedReader.fill(Unknown Source)
        at java.io.BufferedReader.readLine(Unknown Source)
        at java.io.BufferedReader.readLine(Unknown Source)
        at com.aaa.client.ClientInputThread.run(JavaChatClient.java:80)

我认为即使套接字已经关闭，BufferedReader流仍然尝试读取行消息。

但我不知道当客户端终止时，何时以及如何关闭BufferedReader流和套接字连接。

我完全被这部分卡住了。有什么想法吗？

Answer 1

这是因为当调用readline()时，socket是关闭的。您可以首先检查msg，如果msg是\exit，那么首先停止inputthread（使用标志或其他东西），然后将\exit发送到服务器。简而言之，检查/exit->停止inputthread->发送/exit到服务器。

String msg = "";
while (!msg.toLowerCase().equals("/exit")) {
    msg = keyboard.nextLine();

    if (msg.toLowerCase().equals("/exit")) {
        // stop inputThread.
        // make sure inputThread is stopped.
    }

    if (!msg.trim().equals("")) {
        pw.println(msg);
        pw.flush();
    }
}