Need help with thread pool issue..

[Sam Smoot]

First, I will admit up front that this is a homework assignment. I need some guideance, but I am not looking for a final solution. However, I have no other resource at this time to eyeball this with me to see what is missing, so any good nudge will be greatly appreciated.

I have a class DateServer that is supposed to generate multiple threads (5) for a client to access. This is what I have, but...

  
/**
 * Time-of-day server listening to port 6013.
 *
 * To simulate the server delay, sleep a while before generating the date.
 *
 */
 
import java.net.*;
import java.io.*;
import java.util.*;
import java.util.concurrent.*;
 
public class DateServer {
public static void main(String[] args) throws IOException {
NetworkService nws = new NetworkService(6013, 5);
nws.serve();
}
 
}
 
class NetworkService {
 
private final ServerSocket serverSocket;
 
private final ExecutorService pool;
 
public NetworkService(int port, int poolSize) throws IOException {
serverSocket = new ServerSocket(port);
pool = Executors.newFixedThreadPool(poolSize);
}
 
public void serve() {
try {
for (int i = 0; i < 5; i++) {
pool.execute(new Handler(serverSocket.accept()));
System.out.println("looping");
}
} catch (IOException IOE) {
pool.shutdown();
 
}
}
 
class Handler implements Runnable {
 
private final Socket socket;
 
Handler(Socket socket) {
this.socket = socket;
}
 
public void run() {
// read service request
Socket client = new Socket();
try{
client = serverSocket.accept(); 
System.out.println("client = " + client);
// we have a connection 
PrintWriter pout = new PrintWriter(client.getOutputStream(), true); 
// Sleep a while 
int aWhile = (int) (java.lang.Math.random()*5000); java.lang.Thread.sleep(aWhile);
  // write the Date to the socket 
pout.println(new Date().toString());
 
 pout.close(); 
 client.close(); 
  
} catch (Exception err) {
 System.err.println(err); } 

}
 
}
}

I then have a client (DateClient) that is currently only a single thread, but I also have to modify it to create 50 threads to act like there are multiple request accessing the DateServer.

   
/**
 * Client program requesting current date from server.
 *
 * 
 */
 
import java.net.*;
import java.io.*;
 
public class DateClient
{
public static void main(String[] args) throws IOException {
InputStream in = null;
BufferedReader bin = null;
Socket sock = null;
 
try {
sock = new Socket("127.0.0.1",6013);
in = sock.getInputStream();
bin = new BufferedReader(new InputStreamReader(in));
 
String line;


  while( (line = bin.readLine()) != null)
System.out.println("client  " +  line);
}catch(IOException ioe){
System.err.println(ioe);
}
                finally {
                    sock.close();
                }
}
}

Originally, I had a loop around the try block for 50 passes, and it worked on the original server, but only 1 at a time.

Again, I'm not looking for the direct solution, but a good hint in the right direction is greatly appreciated.

[Ken Blair]

Move everything in your main method to a Runnable. Then, in a loop, create a new Thread using that Runnable and start the Thread. Each iteration of the loop will create a new Thread that executes that code and your current Thread will return immediately.

[Sam Smoot]

I'm assuming you are talking about the client part. I'm gonna give it a try and see if it'll work (probably will, I'm really too old for this...)


Thanks for the help!

Sam

[Ken Blair]

Yes. You're attempting to simulate a bunch of concurrent connections right? If you just put it in a loop then it all gets executed sequentially. If instead you move the code to a Runnable and create a loop that makes a bunch of new Threads it will execute more or less concurrently, which sounds like what you want.

[Sam Smoot]

Well, it kinda works, but now the server won't reuse the threads.... How do you make the server recycle the threads on it's end?

/**
 * Time-of-day server listening to port 6013.
 *
 * To simulate the server delay, sleep a while before generating the date.
 *
 */
 
import java.net.*;
import java.io.*;
import java.util.*;
import java.util.concurrent.*;
 
public class DateServer {
public static void main(String[] args) throws IOException {
NetworkService nws = new NetworkService(6013, 5);
nws.serve(5);
}
 
}
 
class NetworkService {
 
private final ServerSocket serverSocket;
 
private final ExecutorService pool;
 
public NetworkService(int port, int poolSize) throws IOException {
serverSocket = new ServerSocket(port);
pool = Executors.newFixedThreadPool(poolSize);
}
 
public void serve(int poolNum) {
try {
for (int i = 0; i < poolNum; i++) {
pool.execute(new Handler(serverSocket.accept()));
System.out.println("Server Thread " + (i+1));
}
} catch (IOException IOE) {
pool.shutdown();
 
}
}
 
class Handler implements Runnable {
 
private final Socket socket;
 
Handler(Socket socket) {
this.socket = socket;
}
 
public void run() {
// read service request 
Socket client = new Socket();

try{
client = serverSocket.accept(); 

// we have a connection 
PrintWriter pout = new PrintWriter(client.getOutputStream(), true); 

// Sleep a while 
//  int aWhile = (int) (java.lang.Math.random()*1000); 
//  java.lang.Thread.sleep(aWhile);
 
   // write the Date to the socket 
      pout.println(new Date().toString());
 
 pout.close(); 
 client.close();
  
} catch (Exception err) {
 System.err.println(err); } 

}
 
}
}

=================

 
 
/**
 * Client program requesting current date from server.
 *
 * 
 */
 
import java.net.*;
import java.io.*;
import java.util.concurrent.*;
 
public class DateClient {


public static void main(String[] args) throws IOException {

   ClientSvc csvc = new ClientSvc("127.0.0.1", 6013, 50);
   csvc.ClientCall(6013,50);
}
}
class ClientSvc{

private final Socket socket;
private final ExecutorService clientPool;

public ClientSvc(String addr, int port, int size) throws IOException{
socket = new Socket(addr, port);
clientPool = Executors.newFixedThreadPool(size);
}

public void ClientCall(int port, int nThread) {
try {
for (int i = 0; i < nThread; i++) {
clientPool.execute(new ClientHandler(socket));
System.out.println(" Client Thread " + (i+1));
}
} catch (Exception ioe) {
clientPool.shutdown();
}
}


}

class ClientHandler implements Runnable{

    private final Socket socket;
    
    ClientHandler(Socket socket){
    this.socket = socket;    
    }
 
public void run() {
InputStream in = null;
BufferedReader bin = null;
Socket sock = null;
try {
sock = new Socket("127.0.0.1", 6013);
in = sock.getInputStream();
bin = new BufferedReader(new InputStreamReader(in));
 
String line;
while ((line = bin.readLine()) != null)
System.out.println("client result: " +  line );
}catch (Exception ioe) {
System.err.println(ioe);
}
}
} 
 

[ March 09, 2006: Message edited by: Sam Smoot ]

[Paul Clapham]

Generally you don't make the server reuse the threads, you just create a new thread whenever the server needs one. Why are you trying to reuse threads?

[Edward Harned]

You�re using the services of pre-written code (Executors, ExecutorService). This relieves the programmer of low-level coding and frees him/her to tackle problem solving.

Live with it, or do it yourself.

If you want to manage a pool of threads, then you�re in for a lot of work. That�s the kind of stuff I like, but then I don�t have a homework assignment to do.