Java网络编程入门（九）之质数判别示例

深碍√TFBOYSˉ_ 2022-05-14 19:18 136阅读 0赞

该示例实现的功能是质数判断，程序实现的功能为客户端程序接收用户输入的数字，然后将用户输入的内容发送给服务器端，服务器端判断客户端发送的数字是否是质数，并将判断的结果反馈给客户端，客户端根据服务器端的反馈显示判断结果。

质数的规则是：最小的质数是2，只能被1和自身整除的自然数。当用户输入小于2的数字，以及输入的内容不是自然数时，都属于非法输入。

网络程序的功能都分为客户端程序和服务器端程序实现，下面先描述一下每个程序分别实现的功能：

1、 客户端程序功能：

a)         接收用户控制台输入

b)         判断输入内容是否合法

c)         按照协议格式生成发送数据

d)         发送数据

e)         接收服务器端反馈

f)          解析服务器端反馈信息，并输出

2、 服务器端程序功能：

a)         接收客户端发送数据

b)         按照协议格式解析数据

c)         判断数字是否是质数

d)         根据判断结果，生成协议数据

e)         将数据反馈给客户端

分解好了网络程序的功能以后，就可以设计网络协议格式了，如果该程序的功能比较简单，所以设计出的协议格式也不复杂。

客户端发送协议格式：

将用户输入的数字转换为字符串，再将字符串转换为byte数组即可。

例如用户输入16，则转换为字符串“16”，使用getBytes转换为byte数组。

客户端发送“quit”字符串代表结束连接

服务器端发送协议格式：

反馈数据长度为1个字节。数字0代表是质数，1代表不是质数，2代表协议格式错误。

例如客户端发送数字12，则反馈1，发送13则反馈0，发送0则反馈2。

功能设计完成以后，就可以分别进行客户端和服务器端程序的编写了，在编写完成以后联合起来进行调试即可。

下面分别以TCP方式和UDP方式实现该程序，注意其实现上的差异。不管使用哪种方式实现，客户端都可以多次输入数据进行判断。对于UDP方式来说，不需要向服务器端发送quit字符串。

以TCP方式实现的客户端程序代码如下：

package example1;

import java.io.*;
    
    import java.net.*;
    
    /**
    
     * 以TCP方式实现的质数判断客户端程序
    
     */
    
    public class TCPPrimeClient {
    
             static BufferedReader br;
    
             static Socket socket;
    
             static InputStream is;
    
             static OutputStream os;
    
             /**服务器IP*/
    
             final static String HOST = "127.0.0.1";
    
             /**服务器端端口*/
    
             final static int PORT = 10005;
    
            
    
             public static void main(String[] args) {
    
                       init(); //初始化
    
                       while(true){
    
                                System.out.println("请输入数字：");
    
                                String input = readInput(); //读取输入
    
                                if(isQuit(input)){ //判读是否结束
    
                                         byte[] b = "quit".getBytes();
    
                                         send(b);
    
                                         break; //结束程序
    
                                }
    
                                if(checkInput(input)){ //校验合法
    
                                         //发送数据
    
                                         send(input.getBytes());
    
                                         //接收数据
    
                                         byte[] data = receive();
    
                                         //解析反馈数据
    
                                         parse(data);
    
                                }else{
    
                                         System.out.println("输入不合法，请重新输入！");
    
                                }
    
                       }
    
                       close(); //关闭流和连接
    
             }
    
            
    
             /**
    
              * 初始化
    
              */
    
             private static void init(){
    
                       try {
    
                                br = new BufferedReader(
    
                                                   new InputStreamReader(System.in));
    
                                socket = new Socket(HOST,PORT);
    
                                is = socket.getInputStream();
    
                                os = socket.getOutputStream();
    
                       } catch (Exception e) {}
    
             }
    
            
    
             /**
    
              * 读取客户端输入
    
              */
    
             private static String readInput(){
    
                       try {
    
                                return br.readLine();
    
                       } catch (Exception e) {
    
                                return null;
    
                       }
    
             }
    
            
    
             /**
    
              * 判断是否输入quit
    
              * @param input 输入内容
    
              * @return true代表结束，false代表不结束
    
              */
    
             private static boolean isQuit(String input){
    
                       if(input == null){
    
                                return false;
    
                       }else{
    
                                if("quit".equalsIgnoreCase(input)){
    
                                         return true;
    
                                }else{
    
                                         return false;
    
                                }
    
                       }
    
             }
    
            
    
             /**
    
              * 校验输入
    
              * @param input 用户输入内容
    
              * @return true代表输入符合要求，false代表不符合
    
              */
    
             private static boolean checkInput(String input){
    
                       if(input == null){
    
                                return false;
    
                       }
    
                       try{
    
                                int n = Integer.parseInt(input);
    
                                if(n >= 2){
    
                                         return true;
    
                                }else{
    
                                         return false;
    
                                }
    
                       }catch(Exception e){
    
                                return false; //输入不是整数
    
                       }
    
             }
    
            
    
             /**
    
              * 向服务器端发送数据
    
              * @param data 数据内容
    
              */
    
             private static void send(byte[] data){
    
                       try{
    
                                os.write(data);
    
                       }catch(Exception e){}
    
             }
    
            
    
             /**
    
              * 接收服务器端反馈
    
              * @return 反馈数据
    
              */
    
             private static byte[] receive(){
    
                       byte[] b = new byte[1024];
    
                       try {
    
                                int n = is.read(b);
    
                                byte[] data = new byte[n];
    
                                //复制有效数据
    
                                System.arraycopy(b, 0, data, 0, n);
    
                                return data;
    
                       } catch (Exception e){}
    
                       return null;
    
             }
    
            
    
             /**
    
              * 解析协议数据
    
              * @param data 协议数据
    
              */
    
             private static void parse(byte[] data){
    
                       if(data == null){
    
                                System.out.println("服务器端反馈数据不正确！");
    
                                return;
    
                       }
    
                       byte value = data[0]; //取第一个byte
    
                       //按照协议格式解析
    
                       switch(value){
    
                       case 0:
    
                                System.out.println("质数");
    
                                break;
    
                       case 1:
    
                                System.out.println("不是质数");
    
                                break;
    
                       case 2:
    
                                System.out.println("协议格式错误");
    
                                break;
    
                       }
    
             }
    
            
    
             /**
    
              * 关闭流和连接
    
              */
    
             private static void close(){
    
                       try{
    
                                br.close();
    
                                is.close();
    
                                os.close();
    
                                socket.close();
    
                       }catch(Exception e){
    
                                e.printStackTrace();
    
                       }
    
             }
    
    }

在该代码中，将程序的功能使用方法进行组织，使得结构比较清晰，核心的逻辑流程在main方法中实现。

以TCP方式实现的服务器端的代码如下：

package example1;
    
    import java.net.*;
    
    /**
    
     * 以TCP方式实现的质数判别服务器端
    
     */
    
    public class TCPPrimeServer {
    
             public static void main(String[] args) {
    
                       final int PORT = 10005;
    
                       ServerSocket ss = null;
    
                       try {
    
                                ss = new ServerSocket(PORT);
    
                                System.out.println("服务器端已启动：");
    
                                while(true){
    
                                         Socket s = ss.accept();
    
                                         new PrimeLogicThread(s);
    
                                }
    
                       } catch (Exception e) {}
    
                       finally{
    
                                try {
    
                                         ss.close();
    
                                } catch (Exception e2) {}
    
                       }
    
                      
    
             }
    
    }
    
    package example1;
    
    import java.io.*;
    
    import java.net.*;
    
    /**
    
     * 实现质数判别逻辑的线程
    
     */
    
    public class PrimeLogicThread extends Thread {
    
             Socket socket;
    
             InputStream is;
    
             OutputStream os;
    
            
    
             public PrimeLogicThread(Socket socket){
    
                       this.socket = socket;
    
                       init();
    
                       start();
    
             }
    
             /**
    
              * 初始化
    
              */
    
             private void init(){
    
                       try{
    
                                is = socket.getInputStream();
    
                                os = socket.getOutputStream();
    
                       }catch(Exception e){}
    
             }
    
            
    
             public void run(){
    
                       while(true){
    
                                //接收客户端反馈
    
                                byte[] data = receive();
    
                                //判断是否是退出
    
                                if(isQuit(data)){
    
                                         break; //结束循环
    
                                }
    
                                //逻辑处理
    
                                byte[] b = logic(data);
    
                                //反馈数据
    
                                send(b);
    
                       }
    
                       close();
    
             }
    
            
    
             /**
    
              * 接收客户端数据
    
              * @return 客户端发送的数据
    
              */
    
             private byte[] receive(){
    
                       byte[] b = new byte[1024];
    
                       try {
    
                                int n = is.read(b);
    
                                byte[] data = new byte[n];
    
                                //复制有效数据
    
                                System.arraycopy(b, 0, data, 0, n);
    
                                return data;
    
                       } catch (Exception e){}
    
                       return null;
    
             }
    
            
    
             /**
    
              * 向客户端发送数据
    
              * @param data 数据内容
    
              */
    
             private void send(byte[] data){
    
                       try{
    
                                os.write(data);
    
                       }catch(Exception e){}
    
             }
    
            
    
             /**
    
              * 判断是否是quit
    
              * @return 是返回true，否则返回false
    
              */
    
             private boolean isQuit(byte[] data){
    
                       if(data == null){
    
                                return false;
    
                       }else{
    
                                String s = new String(data);
    
                                if(s.equalsIgnoreCase("quit")){
    
                                         return true;
    
                                }else{
    
                                         return false;
    
                                }
    
                       }
    
             }
    
            
    
             private byte[] logic(byte[] data){
    
                       //反馈数组
    
                       byte[] b = new byte[1];
    
                       //校验参数
    
                       if(data == null){
    
                                b[0] = 2;
    
                                return b;
    
                       }
    
                       try{
    
                                //转换为数字
    
                                String s = new String(data);
    
                                int n = Integer.parseInt(s);
    
                                //判断是否是质数
    
                                if(n >= 2){
    
                                         boolean flag = isPrime(n);
    
                                         if(flag){
    
                                                   b[0] = 0;
    
                                         }else{
    
                                                   b[0] = 1;
    
                                         }
    
                                }else{
    
                                         b[0] = 2; //格式错误
    
                                         System.out.println(n);
    
                                }
    
                       }catch(Exception e){
    
                                e.printStackTrace();
    
                                b[0] = 2;
    
                       }
    
                       return b;
    
             }
    
            
    
             /**
    
              *
    
              * @param n
    
              * @return
    
              */
    
             private boolean isPrime(int n){
    
                       boolean b = true;
    
                       for(int i = 2;i <= Math.sqrt(n);i++){
    
                                if(n % i == 0){
    
                                         b = false;
    
                                         break;
    
                                }
    
                       }
    
                       return b;
    
             }
    
            
    
             /**
    
              * 关闭连接
    
              */
    
             private void close(){
    
                       try {
    
                                is.close();
    
                                os.close();
    
                                socket.close();
    
                       } catch (Exception e){}
    
             }
    
    }

本示例使用的服务器端的结构和前面示例中的结构一致，只是逻辑线程的实现相对来说要复杂一些，在线程类中的logic方法中实现了服务器端逻辑，根据客户端发送过来的数据，判断是否是质数，然后根据判断结果按照协议格式要求，生成客户端反馈数据，实现服务器端要求的功能。