server can not accept all the clients connection request

[Suresh Khant]

Hi All,

I am implementing NIO and using socket to make connections between the server and the clients , I have got some code
from some sites and from some forums(including this forum) , the code works but the problem is that sometimes some of the clients can not connect to the server
and the server application ignores such connections, can any one Could tell me what is the wrong in the code so that we can enhance the performance of the application
and all clients can connect to the server.

TCPProtocolManager.java

package com.example.nio.socket;

import java.nio.channels.SelectionKey;
import java.nio.channels.SocketChannel;
import java.nio.channels.ServerSocketChannel;
import java.nio.ByteBuffer;
import java.io.IOException;





public class TCPProtocolManager  {

private static TCPProtocolManager tcpProtocolManager = null;
	
	static public TCPProtocolManager getInstance(){
		if(tcpProtocolManager==null)
			tcpProtocolManager= new TCPProtocolManager();
		return tcpProtocolManager;
	}


	public void handleAccept(SelectionKey key) throws IOException {
		//Log.getLogger().debug("HANDLING ACCEPT STARTS");
		SocketChannel clntChan = ((ServerSocketChannel) key.channel()).accept();
		clntChan.configureBlocking(false); 
		clntChan.register(key.selector(), SelectionKey.OP_READ, ByteBuffer.allocate(1024));
	}

	public void handleRead(SelectionKey key) throws IOException {
		//Log.getLogger().debug("HANDLING READ ACCEPTS");
		byte[] receivedPacket;
		SocketChannel clntChan = (SocketChannel) key.channel();
		int bytesRead = 0;
		
		if (key.isValid()){
				
				ByteBuffer buf = (ByteBuffer) key.attachment();
				if (clntChan.isConnected()){
					try{	
						bytesRead = clntChan.read(buf);
						//Log.getLogger().debug("READING CONTENTS OF CHANNEL TO BUFFER");
					}catch(Exception e){
						System.out.println("Error in reading bytebuffer, seems that the corresponding client has been disconnected , so  the client channel "+clntChan +" will be closed");
						clntChan.close();
				}
				buf.clear();
		
				receivedPacket = new byte[buf.capacity()];
				
				
			    buf.get(receivedPacket,0 , receivedPacket.length);
			    //Log.getLogger().info("Received Packet in bytes:"/*+receivedPacket.toString()*/);
			    System.out.println("PACKET(S) HAS BEEN RECEIVED");
			    
				
				if (bytesRead == -1) { // Did the other end close?
					clntChan.close();
				} else if (bytesRead > 0) {
					// Indicate via key that reading/writing are both of interest now.
					key.interestOps(SelectionKey.OP_READ | SelectionKey.OP_WRITE);
				}
				
				
				
			}else
				System.out.println("Key is not valid , seems that the connection is closed");
		}
}

	

	

	public void handleWrite(SelectionKey key,byte[] byteType) throws IOException {
		
			if (key.isValid()){
				ByteBuffer buf = (ByteBuffer) key.attachment();
				buf.clear();
				buf.put(byteType);
				buf.flip(); 
				SocketChannel clntChan = (SocketChannel) key.channel();
				
				if (clntChan.isConnected() && clntChan.isOpen()){
					if (buf.hasRemaining() && buf!=null) {
						try{
							clntChan.write(buf);
						}catch(IOException e){
							System.out.println("Can not Read Data:"+e.getMessage()); 
							clntChan.close();
						}
					}
				}
				if (!buf.hasRemaining()) { 
					key.interestOps(SelectionKey.OP_READ);
				}
				buf.compact(); 
			}
		
		
	}

}

TCPServer.java

package com.example.nio.socket;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.util.Hashtable;
import java.util.Iterator;



/**
 * Servlet implementation class StatusServlet
 */
public class TCPServer extends Thread {
	
	private ServerSocketChannel serverSocketChannel;
	public static boolean stop = false;
	private Selector selector ;
	

	
	
	public static synchronized boolean isStop() {
		return stop;
	}

	public static synchronized void setStop(boolean stop) {
		TCPServer.stop = stop;
		System.out.println("STOPPING THE TCP LISTENER");
	}

	public TCPServer(int port) {
        try {
        	
    		this.selector = Selector.open();
    		this.serverSocketChannel = ServerSocketChannel.open();
    		this.serverSocketChannel.socket().bind(	new InetSocketAddress(port));
    		this.serverSocketChannel.configureBlocking(false); 
    		this.serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
    		System.out.println(" SERVER RUNNING ON PORT " + port);
            this.start();
        } catch (IOException ex) {
        	System.out.println("ERROR WHILE  SERVER RUNNING ON PORT " + port);
            ex.printStackTrace();
        }
    }
	
	/**
     * Close the connection
     */
    @Override
	public void interrupt() {
        super.interrupt();
        try {
        	System.out.println("CLOSING DOWN THE SERVER SOCKET CHANNEL SUCCESSFULLY");
			this.serverSocketChannel.close();
		} catch (IOException e) {
			System.out.println("ERROR IN CLOSING SERVER SOCKET CHANNEL");
			e.printStackTrace();
		}

    }

	
	public void run(){
		
		while (!stop){
				
		while (true) {
			
			try {
				Thread.sleep(5000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			
			try {
				if ((this.selector.select(3000) == 0)){ 
					System.out.println("WAITING FOR THE READY CHANNELS ");
					continue;
				}
			} catch (IOException e1) {
				System.out.println("WAITING FOR THE READY CHANNELS");
				e1.printStackTrace();
			}
			
			Iterator<SelectionKey> keyIter = selector.selectedKeys().iterator();
			while (keyIter.hasNext()) {
				
				SelectionKey key = keyIter.next(); 
					
					if (key.isAcceptable()) {
						//Log.getLogger().debug("TRYING TO ACCPET CONNECTION FROM CLIENT");
						try {
							TCPProtocolManager.getInstance().handleAccept(key);
						} catch (IOException e) {
							System.out.println("ERROR WHILE TRYING TO ACCPET CONNECTION FROM CLIENT");
							e.printStackTrace();
						}
					}
					
					if (key.isReadable()) {
						//Log.getLogger().debug("TRYING TO READ NEW PACKET(S)");
						try {
							TCPProtocolManager.getInstance().handleRead(key);
							
						} catch (IOException e) {
							System.out.println("ERROR WHILE TRYING TO READ NEW PACKET(S)");
							e.printStackTrace();
						}
					}
					keyIter.remove(); 
				}
			//Log.getLogger().debug("TRYING TO CALL PROCESS CURRENT COMMANDS SECOND");
			
	   }
	}
}
	

}

Main.java

/**
 * 
 */
package com.example.nio.socket;


public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		TCPServer tcpServer = new TCPServer(15000);

	}

}

thanks

[Pushkar Choudhary]

Please edit your name to use a real first and last name. See the Naming Policy for more details.

[Rob Spoor]

Pushkar, thanks for helping me out

[Suresh Khant]

Hi Pushkar Choudhary & Rob Prime ,

Thanks for the reply. I have not noticed that rules . but anyhow I have changed my first name and last name.

[Suresh Khant]

Hi All,

Any reply for my post...................

[Suresh Khant]

Hi All,

Any reply for my post...................