java - 客户端-服务器程序中的 while 循环

Question

所以我必须做一些简单的客户端-服务器程序。服务器端`

public static void main(String[] args) throws IOException
{
    ServerSocket ss = null;
    try{ss= new ServerSocket(119);}
    catch(IOException ioe){System.out.println("Can't connect to port.");}

    Socket sock = null;
    try{sock = ss.accept();}
    catch(IOException ioe){System.out.println("Can't connect to client.");}
    System.out.println("Connection successful.");

    PrintStream out = null;
    Scanner in = null;

    try{
        out = new PrintStream(sock.getOutputStream());
        in = new Scanner(sock.getInputStream());
    }catch(Exception e)
    {
        System.out.println("Error.");
    }

    String line;
    String lines = "";

    while((line = in.nextLine()) != null)
    {
        switch(line)
        {
        case "list":out.println("Printing something");break;
        case "loop":
        {
            FileReader fr = new FileReader("D:\\Eclipse\\TestFiles\\text2.txt");
            BufferedReader br = new BufferedReader(fr);
            while((lines = br.readLine()) != null)
            {
                out.println(lines);
            }
            break;
        }
        default:
        {
            if(!(line.equals("end"))) out.println("Unknown command.Try again.");break;
        }
        }
        out.flush();
        if(line.equals("end"))
        {
            out.println("Connection over.");
            break;
        }
    }

    try{
        in.close();
        out.close();
        sock.close();
        ss.close();
    }catch(IOException ioe){}

}

`

客户端

public static void main(String[] args)
{
    Socket sock = null;
    PrintStream out = null;
    Scanner in = null;
    Scanner sIn = null;

    try{
        sock = new Socket("localhost",119);
        out = new PrintStream(sock.getOutputStream());
        in = new Scanner(sock.getInputStream());
        sIn = new Scanner(System.in);
    }catch(Exception e){
        System.out.println("Error connecting to server.");
        System.exit(1);
    }

    System.out.println("Connection successful.");

    String temp = "";

    while((temp = sIn.nextLine()) != null)
    {
        out.println(temp);
        while(in.hasNextLine())System.out.println(in.nextLine());
        out.flush();
        if(temp.equals("end")) break;
    }

    try{
        sock.close();
        in.close();
        out.close();
    }catch(IOException ioe){}

}

我的问题是，在客户端，当第二个 while 循环(第一个 while 循环内的 on)必须结束时，它没有结束，我只是在客户端中输入命令而没有任何响应

Answer 1

修复

1. 使用 PrintWriter 向套接字写入数据，使用 BufferedReader 从套接字读取数据。在自动刷新模式下打开PrintWriter下面的语句中的 true 表示这一点。这样您就不必担心刷新流。

   PrintWriter out = new PrintWriter(sock.getOutputStream(),true);
   

2. 您的结束语句位于循环内，该循环会关闭流，并且您无法将它们用于下一次迭代，因为您将收到异常。将它们从 while 循环中拉出。
3. 在开关中使用不必要的大括号来分隔大小写。
4. 您的连接终止语句应该位于 switch case 之外。只有这样，break 才会对循环而不是开关产生影响。

5. 我使用 br.ready() 来感测流是否已准备好读取，然后迭代循环。这比你的版本有效。

   while((temp = sIn.nextLine()) != null)
   {
       out.println(temp);
       Thread.currentThread().sleep(1000);
       while(in.ready())System.out.println(in.readLine());
       out.flush();
       if(temp.equals("end")) break;
   }
   

6. Thread.currentThread().sleep(1000) 是获取主线程的句柄并将其 hibernate 1000 毫秒，这样我就可以让 br 准备好服务器响应。否则，对于当前请求，br.ready() 将为 false，并且它会在下一次迭代中准备好。我想你知道我想传达什么。

我没有检查案例循环；

服务器

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

public class chatServer
{   
public static void main(String[] args) throws IOException
{
    ServerSocket ss = null;
    try
    {
        ss= new ServerSocket(8000);
    }
    catch(IOException ioe){System.out.println("Can't connect to port.");}

    Socket sock = null;
    try{sock = ss.accept();}
    catch(IOException ioe){System.out.println("Can't connect to client.");}
    System.out.println("Connection successful.");

    PrintWriter out = null;
    Scanner in = null;

    try{
        out = new PrintWriter(sock.getOutputStream(),true);
        in = new Scanner(sock.getInputStream());
    }catch(Exception e)
    {
        System.out.println("Error.");
    }

    String line;
    String lines = "";

    while((line = in.nextLine()) != null)
    {
        switch(line)
        {
            case "list":
                out.println("1. bla  |  2. ble  |  3. bli");break;
            case "group":out.println("Here group will be chosen.");break;
            case "header":out.println("Returns header.");break;
            case "loop":
                FileReader fr = new FileReader("D:\\Eclipse\\TestFiles\\text2.txt");
                BufferedReader br = new BufferedReader(fr);
                while((lines = br.readLine()) != null)
                {
                    out.println(lines);
                }
                break;
            default:
                if(!(line.equals("end")))
                {
                    out.println("Unknown command.Try again.");
                    break;
                }
        }
        if(line.equals("end"))
        {
            out.println("Connection over.");
            break;
        }
    }
    try{
            in.close();
            out.close();
            sock.close();
            ss.close();
        }catch(IOException ioe){}

}

}

客户端

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

public class chatClient
{
public static void main(String[] args) throws IOException, InterruptedException
{
    Socket sock = null;
    PrintStream out = null;
    BufferedReader in = null;
    Scanner sIn = null;

    try
    {
        sock = new Socket("localhost",8000);
        out = new PrintStream(sock.getOutputStream());
        in = new BufferedReader(new InputStreamReader(sock.getInputStream()));
        sIn = new Scanner(System.in);
    }
    catch(Exception e)
    {
        System.out.println("Error connecting to server.");
        System.exit(1);
    }

    System.out.println("Connection successful.");

    String temp = "";

    while((temp = sIn.nextLine()) != null)
    {
        out.println(temp);
        Thread.currentThread().sleep(1000);
        while(in.ready())System.out.println(in.readLine());
        out.flush();
        if(temp.equals("end")) break;
    }

    try
    {
        sock.close();
        in.close();
        out.close();
    }
    catch(IOException ioe){}

}

}