如何实现客户端到客户端的消息通过服务器（聊天）？

Question

我的任务是通过服务器建立一个客户端到客户端的聊天程序。客户端 A 将向服务器发送一条消息，然后转发给客户端 B，反之亦然。所有这一切都将同时发生，直到其中一个关闭它。我有以下程序。

服务器：

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

public class chatServer {

public static Socket s1 = new Socket();
public static Socket s2 = new Socket();
private final static int port1 = 5561;
private final static int port2 = 5562;  

public static void main(String[] args) {    


    try{
        ServerSocket se = new ServerSocket(port1);
        ServerSocket sa = new ServerSocket(port2);
        s1 = se.accept();
        s2 = sa.accept();
    }catch(IOException ioe) {
        System.out.println(ioe);
    }
    System.out.println("##");
    chatServer c = new chatServer();
    chatServer.handler1 h1 = c.new handler1();
    chatServer.handler2 h2 = c.new handler2();

    h1.start();
    h2.start();
}   

public class handler1 extends Thread {

    public void run() {


            try{
                InputStream in = s1.getInputStream();
                System.out.println(s1.isConnected());
                BufferedReader buff = new BufferedReader(new InputStreamReader(in));        
                PrintWriter pout = new PrintWriter(s2.getOutputStream(),true);  
                while(true) {   
                    if(buff!=null) {
                        System.out.println(buff.readLine().toString());
                        pout.println(buff.readLine().toString());
                    }
                }           
            }catch(IOException i){
                System.out.println(i);
            }

    }
}

public class handler2 extends Thread {

    public void run() {

            try{
                InputStream in = s2.getInputStream();
                System.out.println(s2.isConnected());
                BufferedReader buff = new BufferedReader(new InputStreamReader(in));        
                PrintWriter pout = new PrintWriter(s1.getOutputStream(),true);
                while(true) {
                    if(buff!=null) {                    
                        pout.println(buff.readLine().toString());
                        System.out.println(buff.readLine().toString());
                    }
                }
            }catch(IOException i) {
                System.out.println(i);
            }

    }
  }
}

客户端 1：

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



public class client1 {

private final static String IPAddress = "127.0.0.1";
private final static int port = 5561;


public static void main(String[] args) {
    try{
        Socket s = new Socket(IPAddress,port);      
        client2 c = new client2();
        client2.listener l = c.new listener(s);
        client2.publisher p = c.new publisher(s);
        l.start();
        p.start();
    }catch(IOException ioe){
        System.out.println(ioe);
    }
}

public class listener extends Thread {

    Socket s1 = new Socket();
    listener(Socket c){
        s1=c;
    }
    public void run() {
    try{    
    InputStream in = s1.getInputStream();
    BufferedReader b =new BufferedReader(new InputStreamReader(in));

        while(true) {

                    String l = b.readLine();
                    if(l!=null)                 
                        System.out.println(l);

            }
        }catch(IOException ioe) {
                System.out.println(ioe);
            }

    }   
}   

public class publisher extends Thread {

    Socket s2 = new Socket();
    publisher(Socket c){
        s2=c;
    }
    public void run() {
    try {   
        InputStream in = s2.getInputStream();
        BufferedReader b =new BufferedReader(new InputStreamReader(System.in));         
        PrintWriter out = new PrintWriter(s2.getOutputStream(),true);
        while(true) {

                    String str = b.readLine();
                    if(str!=null)   
                        out.println(str);

            }
        }catch(IOException ioe) {
                System.out.println(ioe);
            }   
    }   
 }  
}

客户端 2：

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



public class client2 {

private final static String IPAddress = "127.0.0.1";
private final static int port = 5562;

public static void main(String[] args) {

    try{
        Socket s = new Socket(IPAddress,port);      
        client2 c = new client2();
        client2.listener l = c.new listener(s);
        client2.publisher p = c.new publisher(s);
        l.start();
        p.start();
    }catch(IOException ioe){
        System.out.println(ioe);
    }
}

public class listener extends Thread {

    Socket s1 = new Socket();
    listener(Socket c){
        s1=c;
    }
    public void run() {
    try{

            InputStream in = s1.getInputStream();
            BufferedReader b =new BufferedReader(new InputStreamReader(in));
            PrintWriter out = new PrintWriter(s1.getOutputStream(),true);
        while(true) {
                    String l = b.readLine();
                    if(l!=null)
                        out.println(l);
            }

        }catch(IOException ioe) {
                System.out.println(ioe);
            }
    }   
}   

public class publisher extends Thread {
    Socket s1 = new Socket();
    publisher(Socket c){
        s1=c;
    }
    public void run() {

    try {

            InputStream in = s1.getInputStream();
            BufferedReader b =new BufferedReader(new InputStreamReader(in));                
            BufferedReader b2 = new BufferedReader(new InputStreamReader(in));
        while(true) {

                    String st = b2.readLine();
                    if(st!=null )
                        System.out.println(st);
            }
        }catch(IOException ioe) {
                System.out.println(ioe);
            }   
    }   
 }  
}

以上代码正在运行，没有任何编译器错误。但是没有传递消息。传递的消息显示在相应的客户端上。连接正常。但是沟通没有发生。请指导我完成此操作。

Answer 1

每次调用buff.readLine()，实际上是使用流中的一行。下次调用时，如果有则读取一个新行，否则如果底层流阻塞，调用可能会阻塞。

查看BufferedReader的javaDocs。

因此，当您在循环中调用 readLine 两次时，只有当您的客户端发送至少两行时，您才会看到任何输出，并且转发给另一个客户端的行将是第一个，而第二个将打印到System.out。