java - 无法在套接字列表循环中获取套接字的 DataOutputStream

Question

我正在尝试使用 Java 创建一个客户端/服务器程序，其中客户端将简单的字符串发送到服务器，并且连接到服务器的每个客户端都会获取此字符串。因此，我为服务器创建了 2 个服务器类，它们为每个客户端创建新线程并监听它们。还有一个客户端套接字列表。我想用它向每个客户端发送由其中一个客户端发送的字符串。我为此使用 foreach 循环。但我仅获得将字符串发送到服务器的客户端的 Dataoutputstream:

public void run(){
    try{
        while(true){
            String data = in.readUTF();
            for(Socket soc : GlobalQdaServer.allClients){
                DataOutputStream sOut = new DataOutputStream(soc.getOutputStream());
                sOut.writeUTF(data + ". Total clients number in list: " + GlobalQdaServer.allClients.size());
            }                
        }
    }
    catch(EOFException ex){
        System.out.println(ex.getMessage());
    } 
    catch(IOException ex){
        System.out.println(ex.getMessage());
    } 
}

因此，只有该客户端收到该字符串(它自己发送的)。其他什么也没有收到。这些是完整的类(class):

    import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.*;
import java.util.ArrayList;
import java.util.List;


public class GlobalQdaServer {
    public static List<Socket> allClients = new ArrayList<Socket>();

    public static void main(String[] args) {
        try{
            int serverPort = 7896;
            ServerSocket listenSocket = new ServerSocket(serverPort);
            while(true){
                Socket clientSocket = listenSocket.accept();
                allClients.add(clientSocket);
                Connection c = new Connection(clientSocket);
            }
        }
        catch(IOException ex){
            System.out.println("Server Socket creating failiure");            
        }
    }

}

class Connection extends Thread{
    DataInputStream in;
    DataOutputStream out;
    Socket clientSocket;
    public Connection(Socket aClientSocket){
        try{
            clientSocket = aClientSocket;
            in = new DataInputStream(clientSocket.getInputStream());
            out = new DataOutputStream(clientSocket.getOutputStream());
            this.start();
        }
        catch(IOException ex){
            System.out.println(ex.getMessage());
        }        
    }

    public void run(){
        try{
            while(true){
                String data = in.readUTF();
                for(Socket soc : GlobalQdaServer.allClients){
                    DataOutputStream sOut = new DataOutputStream(soc.getOutputStream());
                    sOut.writeUTF(data + ". Total clients number in list: " + GlobalQdaServer.allClients.size());
                }                
            }
        }
        catch(EOFException ex){
            System.out.println(ex.getMessage());
        } 
        catch(IOException ex){
            System.out.println(ex.getMessage());
        } 
    }
}


    import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.*;


public class GlobalQdaClient {

    public static void main(String[] args) throws IOException {
        int serverPort = 7896;
        Socket s = new Socket("localhost", serverPort);
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String input = "";
        while(!input.equals("end")){
            input = reader.readLine();
            try{
                DataInputStream in = new DataInputStream(s.getInputStream());
                DataOutputStream out = new DataOutputStream(s.getOutputStream());
                out.writeUTF(input);
                String data = in.readUTF();
                System.out.println("Recieved this: " + data);            
            }
            catch(UnknownHostException ex){
                System.out.println(ex.getMessage());
            }
            catch(EOFException ex){
                System.out.println(ex.getMessage());
            }
            catch(IOException ex){
                System.out.println(ex.getMessage());
            }
        }
    }    
}

请帮忙找出问题的根源。我是套接字新手。谢谢

Answer 1

你的程序实际上运行得很好。

唯一的问题是您阻止了客户端的连续读取。

因此，在其他客户端解除阅读阻止后，您实际上会在其他客户端上看到您发送的消息。

尝试以下操作:

• 运行服务器
• 运行客户端1
• 运行客户端2
• 从客户端 1 发送消息(请注意，客户端 2 现在因输入而被阻止)
• 从客户端2发送消息

现在您将在客户端 2 上看到之前从客户端 1 发送的消息。

但是，如果您需要两个客户端在消息发送后都接收消息，则需要创建另一个线程来连续获取更新。

我已经修改了您的客户端来执行此操作。

import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.*;
import java.util.logging.Level;
import java.util.logging.Logger;


public class GlobalQdaClient extends Thread {
        int serverPort = 7896;
        BufferedReader reader ;
        static String input = "";
        Socket s;
        DataInputStream in ;
        DataOutputStream out ;
public GlobalQdaClient() {
        try {
            reader  = new BufferedReader(new InputStreamReader(System.in));
             s = new Socket("localhost", serverPort);
             in = new DataInputStream(s.getInputStream());
             out = new DataOutputStream(s.getOutputStream());
        } catch (IOException ex) {
            Logger.getLogger(GlobalQdaClient.class.getName()).log(Level.SEVERE, null, ex);
        }
}

public static void main(String[] args) throws IOException {
    GlobalQdaClient client = new GlobalQdaClient();
    client.start();
    while(!client.input.equals("end")){
        client.input = client.reader.readLine();
        try{
            client.out.writeUTF(client.input);
            if(client.in.available()>0){
            String data = client.in.readUTF();
            System.out.println("Recieved this: " + data);            
            }
        }
        catch(UnknownHostException ex){
            System.out.println(ex.getMessage());
        }
        catch(EOFException ex){
            System.out.println(ex.getMessage());
        }
        catch(IOException ex){
            System.out.println(ex.getMessage());
        }
    }
}    

@Override
public void run(){

    try {
        while(true){
            String data = in.readUTF();
            System.out.println("Recieved this: " + data);            
            }    
    } catch (IOException ex) {
            Logger.getLogger(Message.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

}