扩展服务器代码，以便服务器能够使用多线程与客户端进行交互。因此，没有客户端 sim 连接同一台服务器

Question

*无法弄清楚上面的问题。已经尝试过oracle教程并注意但是我仍然无法做到。任何帮助将不胜感激。

Blackboard上给出的权重转换服务器（ConversionServerNoConcurrency.java）可以与多个交互 客户端，但只能以顺序方式（即新客户端实例只有在服务器连接 完成与前一个客户的交易）。 扩展/修改给定的服务器代码，以便服务器能够与多个客户端并行（同时）交互， 使用多线程。不应限制同时连接到同一台服务器的客户端数量。

确实需要一些代码方面的帮助，否则我在做作业时将无法暗示它

import java.io.*;
import java.net.*;
import java.util.Scanner;
public class ConversionServerNoConcurrency {
private Socket s;
private Scanner in;
private PrintWriter out;
public static void main(String[] args) throws IOException {

    ServerSocket server = new ServerSocket(8888);

    ConversionServerNoConcurrency serverInstance = new         ConversionServerNoConcurrency();

    System.out.println("Server running. Waiting for a client to connect...");

    while (true) {

        serverInstance.s = server.accept();

        System.out.println("Client connected");

        serverInstance.run();

        System.out.println("Client disconnected. Waiting for a new client to connect...");
    }
}
public void run() {
    try {
        try {

            in = new Scanner(s.getInputStream());

            out = new PrintWriter(s.getOutputStream());

            doService(); 

        } finally {
            s.close();
        }
    } catch (IOException e) {
        System.err.println(e);
    }
}
public void doService() throws IOException {

    while (true) {

        if (!in.hasNext())
            return;

        String request = in.next();

        System.out.println("Request received from client: \'" + request + "\'");

        if (!request.equals("QUIT")) // end connection with this client 
            handleConversionRequest(request);

    }
}
public void handleConversionRequest(String request) {

    String amountStr = in.next();

    double amount = Double.valueOf(amountStr);

    System.out.println("Amount received from client: " + amount);

    if (request.equals("CONVERT_TO_POUNDS")) {
        out.println(amount * 2.2d); // send conversion result to client
        System.out.println("Sent conversion result to client");
    } else if (request.equals("CONVERT_TO_KGS")) {
        out.println(amount / 2.2d); 
        System.out.println("Sent conversion result to client");
    } else
        System.err.println("Unknown request!");

       out.flush();
     }
}

 

import java.io.*;
import java.net.Socket;
import java.util.Scanner;


public class ConversionClient {

    public static void main(String[] args) throws IOException, InterruptedException{
        Socket s = new Socket("localhost", 8888);
        InputStream instream= s.getInputStream();
        OutputStream outstream= s.getOutputStream();
        Scanner in = new Scanner(instream);
        PrintWriter out = new PrintWriter(outstream);
        out.print("CONVERT_TO_KGS 123.45\n");  // we send the 1st request to the server
        out.flush();
        String response = in.nextLine();
        System.out.println("Received from server: " + response);
        Thread.sleep(2000); // delay the next request a bit
        out.print("CONVERT_TO_POUNDS 56\n");  // 2nd request
        out.flush();
        response = in.nextLine();
        System.out.println("Received from server: " + response);
        Thread.sleep(2000); // delay the next request a bit
        out.print("CONVERT_TO_POUNDS 836.98\n");  // 3rd request
        out.flush();
        response = in.nextLine();
        System.out.println("Received from server: " + response);
        out.print("QUIT\n");  
        out.flush();
        s.close();
    }

}

Answer 1

编写面向并发连接的服务器是计算机科学/软件工程中的一门重要学科。因此，即使您不知道如何编码，您也必须了解以下内容。

1. 在像ConversionServerNoConcurrency 这样的迭代式面向连接服务器中，它将只有一个线程（主线程）接收连接和服务连接。
2. 如果您想开发面向并发连接的服务器，您需要将接收连接和服务连接分成两个不同的线程。
3. 如果您在下面看到ConversionServerConcurrency，则连接接收由主线程完成，并将连接服务委托给execService 池中的线程。使用线程池来避免 DDoS 攻击很重要。因为在线程池中，可以生成的线程数量有一个最大限制。

4. 看看ConversionServerTask，它现在拥有服务连接的所有逻辑。

   import java.io.*;
   import java.net.*;
   import java.util.Scanner;
   import java.util.concurrent.*;
   public class ConversionServerConcurrency {
   
   public static void main(String[] args) throws IOException {
   
       ServerSocket server = new ServerSocket(8888);
   
       System.out.println("Server running. Waiting for a client to connect...");
   
       ExecutorService execService = Executors.newFixedThreadPool(10);
   
       while (true) {
   
           Socket clientSocket = server.accept();
   
           execService.submit(new ConversionServerTask(clientSocket));
   
           System.out.println("Waiting for a new client to connect...");
       }
   }
   
   public static class ConversionServerTask implements Runnable {
       private Socket s;
       private Scanner in;
       private PrintWriter out;
   
       public ConversionServerTask(Socket clientSocket) {
           this.s = clientSocket;
       }
   
   
       public void run() {
           System.out.println("Client connected");
           try {
               try {
   
                   in = new Scanner(s.getInputStream());
   
                   out = new PrintWriter(s.getOutputStream());
   
                   doService();
   
               } finally {
                   s.close();
               }
           } catch (IOException e) {
               System.err.println(e);
           } finally {
               System.out.println("Client disconnected");
           }
       }
       public void doService() throws IOException {
   
           while (true) {
   
               if (!in.hasNext())
                   return;
   
               String request = in.next();
   
               System.out.println("Request received from client: \'" + request + "\'");
   
               if (request.equals("QUIT")) {// end connection with this client 
                   break;
               } else {
                   handleConversionRequest(request);
               }
   
           }
       }
       public void handleConversionRequest(String request) {
   
           String amountStr = in.next();
   
           double amount = Double.valueOf(amountStr);
   
           System.out.println("Amount received from client: " + amount);
   
           if (request.equals("CONVERT_TO_POUNDS")) {
               out.println(amount * 2.2d); // send conversion result to client
               System.out.println("Sent conversion result to client");
           } else if (request.equals("CONVERT_TO_KGS")) {
               out.println(amount / 2.2d);
               System.out.println("Sent conversion result to client");
           } else
               System.err.println("Unknown request!");
   
           out.flush();
       }
   }
   
   
   }