无法向所有客户端 Java 发送消息

Question

I'm working with A Server which can receive message from all clients and send them to others. I can receive message but I cant sen to all clients although I get the correct out Stream from all clients.

This is my code If you want to test, please cmd -> telnet localhost port number

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

public class Server 
{

    private ServerSocket s;
    private Hashtable saveOutputStreams =  new Hashtable(500,80);

    //Constructor
    public Server(int port) throws IOException
    {
        listen(port);
    }
    //Listen method
    public void listen(int port) throws IOException
    {
        s = new ServerSocket(port);

        while(true)
        {
            Socket incoming = s.accept();

            OutputStream sout = incoming.getOutputStream();

            saveOutputStreams.put(incoming, sout);
            Runnable r = new ThreadHandler(this,incoming);
            Thread t = new Thread(r);
            t.start();
        }
    }
    // Create a table of streams to process in for loop of senToAll method
    Enumeration getOutputStreams()
    {
        return saveOutputStreams.elements();
    }
    // Send message to all clients
    public void sendToAll(String message)
    {
        synchronized(saveOutputStreams)
        {
            for(Enumeration e = getOutputStreams();e.hasMoreElements();)
            {

                OutputStream getOut = (OutputStream)e.nextElement();
                PrintWriter outp  = new PrintWriter(getOut);

                try
                {
                    outp.println("sent"+ message);
                    System.out.println("Stream: "+getOut);
                    System.out.println("PrinWriter "+outp);

                }
                catch(Exception ie)
                {
                    ie.printStackTrace();
                    System.out.println("Error");
                }

                finally
                {
                    System.out.println("done sen To All");
                }
            }
        }
    }
    // Main
    public static void main(String []args) throws IOException
    {
        new Server(8015);
    }
}

class ThreadHandler implements Runnable
{
    private Socket incoming;
    private Server serverP;

    public ThreadHandler(Server server, Socket socket)
    {
        serverP = server;
        incoming = socket;
    }

    public synchronized void run()
    {
        try
        {
            try
            {

                InputStream inStream = incoming.getInputStream();
                OutputStream outStream = incoming.getOutputStream();

                Scanner in = new Scanner(inStream);
                PrintWriter out = new PrintWriter(outStream,true);

                out.println("TungAnh'Server");
                String message = in.nextLine();
                serverP.sendToAll(message);

                out.println("receieve: "+message);
                out.println("done");
                System.out.println("current Stream: "+ outStream);
                System.out.println("PrinWriter "+ out);

            }
            finally
            {
                incoming.close();
            }
        }
        catch(IOException e)
        {
            e.printStackTrace();
        }
    }
}

Answer 1

I improved your code a little bit:

1. Weird logging removed
2. Added instances management
3. Added some streams closing
4. ...

If you are going to use my code, you should definitely have a look at synchronization (my methods are synchronized, but they should be synchronized with the same locking object/class) and exception handling. I could not spend more time with this issue, sorry for that.

Result (works for me):

package test;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Server 
{

    private ServerSocket s;

    //Constructor
    public Server(int port) throws IOException
    {
        listen(port);
    }
    //Listen method
    public void listen(int port) throws IOException
    {
        s = new ServerSocket(port);

        while(true)
        {
            Socket incoming = s.accept();
            Runnable r = new ThreadHandler(this,incoming);
            Thread t = new Thread(r);
            t.start();
        }
    }

    // Main
    public static void main(String []args) throws IOException
    {
        new Server(8015);
    }
}

class ThreadHandler implements Runnable
{
    private Socket incoming;

    private static List<ThreadHandler> instances = new ArrayList<ThreadHandler>();

    public synchronized void addInstance() {
        instances.add(this);
    }

    public synchronized void removeInstance() {
        instances.remove(this);
    }

    public ThreadHandler(Server server, Socket socket)
    {
        incoming = socket;
        addInstance();
    }

    public synchronized void sendToAll(String msg, ThreadHandler me) {
        for (ThreadHandler h : instances) {
            if (h == me) continue;

            OutputStream outStream = null;
            PrintWriter print = null;
            try {
                outStream = h.incoming.getOutputStream();
                print = new PrintWriter(outStream);
                print.println(msg);
                print.flush();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }

    public synchronized void run()
    {
        try
        {
            try
            {

                InputStream inStream = incoming.getInputStream();
                OutputStream outStream = incoming.getOutputStream();

                Scanner in = null;
                try {
                    in = new Scanner(inStream);

                    PrintWriter out = new PrintWriter(outStream,true);

                    out.println("Vojta's Server");

                    while (true) {
                        try {
                            String message = in.nextLine();
                            sendToAll(message, this);
                        } catch (Exception e) {

                        }

                    }


                } catch (Exception e) {

                }
                finally {
                    if (in != null) {
                        in.close();
                    }
                }
            }
            finally
            {
                incoming.close();
            }
        }
        catch(IOException e)
        {
            e.printStackTrace();
        } finally {
            removeInstance();
        }
    }
}