Java聊天服务器

Question

仅供参考这是作业。我必须构建一个Java聊天服务器。我已经能够构建一个与1个客户端通信的服务器。但我需要这个与多个用户沟通。

用户应输入他们希望与之交谈的人名，然后输入破折号（ - ），然后输入要发送的消息。我能够让用户登录但我无法获得要打印的用户列表或要发送给其他用户的消息。这是服务器代码：

/** 
    Threaded Server
*/

import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Set;

public class ThreadedServer
{
    public static void main( String[] args) throws Exception
    {
        HashMap<String, Socket> users = new HashMap<String, Socket>( );
        ServerSocket server = new ServerSocket(5679);
        System.out.println( "THE CHAT SERVER HAS STARTED! =)" );
        while(true)
        {
            Socket client = server.accept();
            ThreadedServer ser = new ThreadedServer();
            ClientFromThread cft =ser.new ClientFromThread(client);
            String name = cft.getUserName();
            users.put( name, client );
            cft.giveUsersMap( users );
            //cft.giveOnlineUsers( ); //DOES NOT WORK YET!!!!
            System.out.println("Threaded server connected to " 
                        + client.getInetAddress() + "  USER: " + name );            
        } 

    }

    //***************************************************************************************************

    class ClientFromThread extends Thread
    {
        private Socket client;
        private Scanner fromClient;
        private PrintWriter toClient;
        private String userName;
        HashMap<String, Socket> users;

        public ClientFromThread( Socket c ) throws Exception
        {
            client = c;
            fromClient = new Scanner( client.getInputStream() );
            toClient = new PrintWriter( client.getOutputStream(), true );
            userName = getUser();
            start();
        }
        public void giveUsersMap( HashMap<String, Socket> users )
        {
            this.users = users;
        }

        //THIS DOESNT WORK YET... IT PRINTS THE FIRST LINE BUT NOT THE LIST
        public void giveOnlineUsers()
        {
            toClient.println("These users are currently online:");
            Set<String> userList = users.keySet();
            String[] userNames = null;
            userList.toArray( userNames );

            for( int i = 0; i< userNames.length; i++ )
            {
                toClient.println(userNames[i]);
            }
        }

        public String getUserName()
        {
            return userName;
        }

        private String getUser()
        {
            String s = "";
            while( (s.length() < 1) || (s == null) )
            {
                toClient.println("What is your first name? ");
                s=fromClient.nextLine().trim();
            }
            toClient.println("Thank You! Welcome to the chat room " + s + ".");
            return s.toUpperCase();
        }

        public void run() 
        {
            String s = null;
            String toUser;
            String mesg;

            while( (s=fromClient.nextLine().trim()) != null )
            {
                if( s.equalsIgnoreCase( "END" )) break;

                for( int i=0; i<s.length(); i++)
                {
                    if( s.charAt(i) == '-' )
                    {
                        toUser = s.substring( 0, i ).trim().toUpperCase();
                        mesg = s.substring( i+1 ).trim();
                        Socket client = users.get( toUser );
                        try
                        {
                            ClientToThread ctt = new ClientToThread(client);
                            ctt.sendMesg( mesg, toUser );
                            ctt.start();
                        }
                        catch(Exception e){e.printStackTrace();}
                        break;
                    }
                    if( (i+1) == s.length() )
                    {
                        toClient.println("Sorry the text was invalid. Please enter a user name " +
                                                     "followed by a dash (-) then your message.");
                    }
                }
            }
            try
            {
                fromClient.close();
                toClient.close();
                client.close();
            }
            catch(Exception e){e.printStackTrace();}
        }

    } //end class ClientFromThread

    //***************************************************************************************************

    class ClientToThread extends Thread
    {
        private Socket client;
        private PrintWriter toClient;
        private String mesg;

        public ClientToThread( Socket c ) throws Exception
        {
            client = c;
            toClient = new PrintWriter( client.getOutputStream(), true );
        }

        public void sendMesg( String mesg, String userName )
        {
            this.mesg = userName + ": " + mesg;
        }
        public void run() 
        {
            toClient.println(mesg);

            try
            {
                toClient.close();
                client.close();
            }
            catch(Exception e){e.printStackTrace();}
        }

    } //end class ClientToThread

    //***************************************************************************************************

} //end class ThreadedServer

这是客户端代码“

import java.net.Socket;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;


public class ReverseClient 
{
public static void main( String[] args ) throws Exception
{
    String line = null;
    Socket server= new Socket( "10.0.2.103", 5679);
    System.out.println( "Connected to host: " + server.getInetAddress() );
    BufferedReader fromServer = new BufferedReader(
                new InputStreamReader(server.getInputStream()) );
    PrintWriter toServer = new PrintWriter( server.getOutputStream(), true );
    BufferedReader input = new BufferedReader( 
                new InputStreamReader(System.in) );
    while( (line=input.readLine()) !=null )
    {
        toServer.println(line);
        System.out.println( fromServer.readLine() );
    }
    fromServer.close();
    toServer.close();
    input.close();
    server.close();

}   
}

这是控制台输出（顶部是服务器，底部是客户端）：

我收到错误（如上图所示）并且邮件没有发送。有关如何处理这些问题的任何建议？

Answer 1

到目前为止，我发现这是一个问题，但我不认为这是唯一的问题..

这将有助于NoSuchElementException在第90行周围更改此...

while( (s=fromClient.nextLine().trim()) != null )
{

对...

while(fromClient.hasNext())
{
   s = fromClient.nextLine().trim();

确定刚刚在ClientToThread.run（）中发现了另一个问题...您在发送第一条消息后关闭了客户端连接。我把它们都评论出来，似乎工作得更好一些。

public void run()
  {
     toClient.println(mesg);
     try {
        //toClient.close();
        //client.close();
     }
     catch (Exception e)  {
        e.printStackTrace();
     }
  }

Answer 2

您的第一个问题是解析来自用户的消息。

循环遍历字符串，它有两个选项之一，字符是短划线或无效。

因此，理想情况下，您应该在破折号之前收到用户名中字符数的无效消息。

您应该使用String.indexOf来确定破折号的位置，然后将消息拆分为两部分，如果indexOf的结果为-1，则它是无效消息。