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Threads in an instant messaging program

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Join Date: Nov 2009

Posts: 5

Reputation: eleal is an unknown quantity at this point

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eleal

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Threads in an instant messaging program

22 Days Ago

I'm trying to write an instant messaging program in Java. What I have coded so far, goes like this: Each client connects to a thread created by the server, to which he/she sends the message. My doubt is, how can I kill all the threads that have been created by the main program when the administrator presses de 'q' in the keyboard. I made a class for a thread whose only function is to read the 'q' from the keyboard, but, how can I notify to the main program that it must kill all the threads?

This is the Server (it is not complete):

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 Java Syntax (Toggle Plain Text) 
public class Server {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = null;
        boolean listening = true;
		new StdinReaderThread();
 
        try {
            serverSocket = new ServerSocket(4444);
        } catch (IOException e) {
            System.err.println("Could not create socket");
            System.exit(-1);
        }
 
        while (listening){
        	new ServerThread(serverSocket.accept()).start();
		}
        serverSocket.close();
    }
}
public class Server {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = null;
        boolean listening = true;
		new StdinReaderThread();

        try {
            serverSocket = new ServerSocket(4444);
        } catch (IOException e) {
            System.err.println("Could not create socket");
            System.exit(-1);
        }

        while (listening){
        	new ServerThread(serverSocket.accept()).start();
		}
        serverSocket.close();
    }
}

This is the thread which reads 'q' from keyboard:

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 Java Syntax (Toggle Plain Text) 
public class StdinReaderThread implements Runnable{
		BufferedReader stdin;
 
		public StdinReaderThread(){
			Thread subpr = new Thread(this,"x");
			stdin = new BufferedReader( new InputStreamReader(System.in));
			subpr.start();
		}
		public void run(){
			while (true){
			   try{
			      String stdinline = stdin.readLine();
			      if( stdinline.startsWith("q")){
				    System.out.println("end");
			       }
				  else if( stdinline.startsWith("m"))
					System.out.println("send message");
				  else if( stdinline.startsWith("l"))
					System.out.println("send login");
				  else if( stdinline.startsWith("u"))
					System.out.println("list users");
			    } catch (Exception e){}
		    }
        }
}
public class StdinReaderThread implements Runnable{
		BufferedReader stdin;

		public StdinReaderThread(){
			Thread subpr = new Thread(this,"x");
			stdin = new BufferedReader( new InputStreamReader(System.in));
			subpr.start();
		}
		public void run(){
			while (true){
			   try{
			      String stdinline = stdin.readLine();
			      if( stdinline.startsWith("q")){
				    System.out.println("end");
			       }
				  else if( stdinline.startsWith("m"))
					System.out.println("send message");
				  else if( stdinline.startsWith("l"))
					System.out.println("send login");
				  else if( stdinline.startsWith("u"))
					System.out.println("list users");
			    } catch (Exception e){}
		    }
        }
}

Last edited by eleal; 22 Days Ago at 2:42 pm.

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Join Date: May 2008

Posts: 54

Reputation: gangsta1903 is an unknown quantity at this point

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gangsta1903 gangsta1903 is offline

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Junior Poster in Training

22 Days Ago

with

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join();

if you keep all the threads you created in an array,vector...
then you can call join() on all threads to kill them all...Of course, this will cause all threads to be done.

If you mean stopping server imediately, then just close the server...
server.close();

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Join Date: Nov 2009

Posts: 5

Reputation: eleal is an unknown quantity at this point

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eleal

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Newbie Poster

22 Days Ago

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Originally Posted by gangsta1903

with
Help with Code Tags

java Syntax (Toggle Plain Text)
join();
join();
if you keep all the threads you created in an array,vector...
then you can call join() on all threads to kill them all...Of course, this will cause all threads to be done.

If you mean stopping server imediately, then just close the server...
server.close();

Thanks gangsta1903,
But how can I notify the main program that it's child thread StdInReaderThread has just detected a 'q' from the keyboard ? And, what happens if the main program is blocked on a socket and StdInReaderThread detects a 'q'?

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Join Date: May 2008

Posts: 54

Reputation: gangsta1903 is an unknown quantity at this point

Solved Threads: 1

gangsta1903 gangsta1903 is offline

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Junior Poster in Training

22 Days Ago

•

Originally Posted by eleal

Thanks gangsta1903,
But how can I notify the main program that it's child thread StdInReaderThread has just detected a 'q' from the keyboard ? And, what happens if the main program is blocked on a socket and StdInReaderThread detects a 'q'?

Your approach is right. On server side, before starting the server-client mechanism, first start your stdInReaderThread. Its up to you what to do when you get "q". You can just close the server. But,for example if its a file sharing program, then you should probably wait last file transfer before closing. But in your program its just messaging, so just closing the server will serve the purpose...
What I mean, there wont be a blocking... Client sends message and it comes instantly, its not a long lasting process. Of course when you close the server, messaging if any will be interrupted.

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Join Date: May 2008

Posts: 54

Reputation: gangsta1903 is an unknown quantity at this point

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gangsta1903 gangsta1903 is offline

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22 Days Ago

 Help with Code Tags 
 java Syntax (Toggle Plain Text) 
public class Server {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = null;
        boolean listening = true;
        // start the stdinReader first
	new StdinReaderThread().start();
 
        try {
            serverSocket = new ServerSocket(4444);
        } catch (IOException e) {
            System.err.println("Could not create socket");
            System.exit(-1);
        }
 
        while (listening){
        	new ServerThread(serverSocket.accept()).start();
		}
        serverSocket.close();
    }
}
public class Server {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = null;
        boolean listening = true;
        // start the stdinReader first
	new StdinReaderThread().start();

        try {
            serverSocket = new ServerSocket(4444);
        } catch (IOException e) {
            System.err.println("Could not create socket");
            System.exit(-1);
        }

        while (listening){
        	new ServerThread(serverSocket.accept()).start();
		}
        serverSocket.close();
    }
}