Question

我已经搜索了答案，但无法完全解决该代码。我希望客户端将数字发送到服务器，服务器将2个数字加起来并发回。问题是，客户端将它们发送到服务器，服务器将它们加起来（至少我认为是这样），但是它什么也没有发回。我现在正在发布客户端代码：

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        InetSocketAddress ep = new InetSocketAddress("127.0.0.1", 1234);
        String broj1, broj2;
        Scanner sc = new Scanner(System.in);
        System.out.print("Unesite 1. broj: ");
        broj1 = sc.nextLine();
        System.out.println();
        System.out.print("Unesite 2. broj: ");
        broj2 = sc.nextLine();
        if(broj1.contains("[a-zA-Z+]")==true&&broj2.contains("[a-zA-Z+]")){
            System.out.println("Niste unijeli brojeve.");
            System.exit(0);
        }
        byte[] brojJedan = new byte[256];
        byte[] brojDva = new byte[256];
        brojJedan = broj1.getBytes();
        brojDva = broj2.getBytes();
        DatagramPacket packet1 = new DatagramPacket(brojJedan, brojJedan.length, ep);
        DatagramPacket packet2 = new DatagramPacket(brojDva, brojDva.length, ep);
        try(DatagramSocket Klijent = new DatagramSocket(1000)){
            Klijent.send(packet1);
            Klijent.send(packet2);
            byte[] rezultat = new byte[256];
            DatagramPacket packetRezultat = new DatagramPacket(rezultat, rezultat.length, ep);
            Klijent.receive(packetRezultat);
            System.out.println(new String(packetRezultat.getData(), 0, packetRezultat.getLength()));
        }catch(Exception ex){}
    }
}

服务器代码：

import java.awt.*;
import java.net.*;
import java.nio.ByteBuffer;

public class Main{
    public static void main(String[] args) {
        try {
            DatagramSocket serverSocket = new DatagramSocket(1234);
            byte[] buff1 = new byte[256];
            byte[] buff2 = new byte[256];
            byte[] buffRezultat = new byte[256];
            while(true){
                System.out.println("Client connected.");
                DatagramPacket p1 = new DatagramPacket(buff1,buff1.length);
                DatagramPacket p2 = new DatagramPacket(buff2, buff2.length);
                serverSocket.receive(p1);
                System.out.println("p1 recieved");
                serverSocket.receive(p2);
                System.out.println("p2 recieved");
                int rezultat, brojJedan, brojDva;
                brojJedan = ByteBuffer.wrap(p1.getData()).getInt();
                brojDva = ByteBuffer.wrap(p2.getData()).getInt();
                System.out.println("byte converted to int");
                rezultat = brojJedan+brojDva;
                System.out.println("numbers added");
                buffRezultat = ByteBuffer.allocate(1).putInt(rezultat).array();
                DatagramPacket pRez = new DatagramPacket(buffRezultat, buffRezultat.length);
                serverSocket.send(pRez);
                System.out.println("res sent");
            }
        }catch(Exception ex){}

    }
}```

Answer 1

您的代码包含许多问题：

在客户端：

您正在将String放入出站byte[]，同时期望服务器端有int。
您正在将端口1000与DatagramSocket一起使用，而不应该使用任何端口。
您期望从入站String获得byte[]，同时在服务器端将int放入其中。

在服务器端：

要从int接收一个byte[]（32位），您必须读取四个字节（每个8位）。
要通过ìnt发送一个byte[]，您必须分配四个字节。
从服务器发送回客户端的DatagramPacket需要知道客户端的地址和端口。

此代码有效：

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.util.Scanner;

public class Client {
    public static void main(String[] args) {
        InetSocketAddress ep = new InetSocketAddress("127.0.0.1", 1234);
        String broj1, broj2;
        Scanner sc = new Scanner(System.in);
        System.out.print("Unesite 1. broj: ");
        broj1 = sc.nextLine();
        System.out.println();
        System.out.print("Unesite 2. broj: ");
        broj2 = sc.nextLine();
        if(broj1.contains("[a-zA-Z+]")&&broj2.contains("[a-zA-Z+]")){
            System.out.println("Niste unijeli brojeve.");
            System.exit(0);
        }
        byte[] brojJedan = ByteBuffer.allocate(4).putInt(Integer.parseInt(broj1)).array();
        byte[] brojDva = ByteBuffer.allocate(4).putInt(Integer.parseInt(broj2)).array();
        DatagramPacket packet1 = new DatagramPacket(brojJedan, brojJedan.length, ep);
        DatagramPacket packet2 = new DatagramPacket(brojDva, brojDva.length, ep);
        try(DatagramSocket Klijent = new DatagramSocket()){
            Klijent.send(packet1);
            Klijent.send(packet2);
            byte[] rezultat = new byte[256];
            DatagramPacket packetRezultat = new DatagramPacket(rezultat, rezultat.length, ep);
            Klijent.receive(packetRezultat);
            System.out.println(ByteBuffer.wrap(packetRezultat.getData(), 0, 4).getInt());
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}


import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.nio.ByteBuffer;

public class Server {
    public static void main(String[] args) {
        try {
            DatagramSocket serverSocket = new DatagramSocket(1234);
            byte[] buff1 = new byte[256];
            byte[] buff2 = new byte[256];
            byte[] buffRezultat = new byte[256];
            while (true) {
                System.out.println("Client connected.");
                DatagramPacket p1 = new DatagramPacket(buff1, buff1.length);
                DatagramPacket p2 = new DatagramPacket(buff2, buff2.length);
                serverSocket.receive(p1);
                System.out.println("p1 recieved");
                serverSocket.receive(p2);
                System.out.println("p2 recieved");
                int rezultat, brojJedan, brojDva;
                brojJedan = ByteBuffer.wrap(p1.getData(), 0, 4).getInt();
                brojDva = ByteBuffer.wrap(p2.getData(), 0, 4).getInt();
                System.out.println("byte converted to int" + brojDva + " " + brojJedan);
                rezultat = brojJedan + brojDva;
                System.out.println("numbers added " + rezultat);
                buffRezultat = ByteBuffer.allocate(4).putInt(rezultat).array();
                DatagramPacket pRez = new DatagramPacket(buffRezultat, buffRezultat.length, p2.getAddress(), p2.getPort());
                serverSocket.send(pRez);
                System.out.println("res sent");
            }
        } catch (Exception ex) {
        }
    }
}

虽然此代码可以工作（对于某些输入），但它仍然存在一些弱点：

输入验证仅检查是否不使用字母。这并不一定给您提供电话号码（请查看此post）。
您无需发送两个DatagramPacket即可传输两个int；一个就够了。
使用标准I / O流将帮助您写入和读取字节数组。
实施有意义的异常消息将帮助您编写代码和用户使用该软件。

客户端将号码发送给服务器，但服务器不会将其发回

1 个答案: