I am writing a auction server and client and using a class called BidHandler to deal with
the bids another class AuctionItem to deal with
the items for auction.
The main problem I am having is little synchroization problem.
Screen output of client server
as can see from
the image at 1st it takes
the new bid and changes
the value of
the time to it, but when one
the user enters 1.0
the item seems to be changed to that. But later on when
the bid changes again to 15.0 it seems to stay at that price. Is there any reason for that. I have included my code below. Sorry if didnt explain this well.
This is
the auction client
import java.io.*;
import java.net.*;
public class AuctionClient
{
private AuctionGui gui;
private Socket socket;
private DataInputStream dataIn;
private DataOutputStream dataOut;
//Auction Client constructor String name used as identifier for each client to allow server to pick
the winning bidder
public AuctionClient(String name,String server, int port)
{
gui =
new AuctionGui("Bidomatic 5000");
gui.input.addKeyListener (new EnterListener(this,gui));
gui.addWindowListener(new ExitListener(this));
try
{
socket =
new Socket(server, port);
dataIn =
new DataInputStream(socket.getInputStream());
dataOut =
new DataOutputStream(socket.getOutputStream());
dataOut.writeUTF(name);
while (true)
{
gui.output.append("\n"+dataIn.readUTF());
}
}
catch (Exception e)
{
e.printStackTrace();
}
}
public void sentBid(String bid)
{
try
{
dataOut.writeUTF(bid);
}
catch(IOException e)
{
e.printStackTrace();
}
}
public void disconnect()
{
try
{
socket.close();
}
catch(IOException e)
{
e.printStackTrace();
}
}
public static void main (String args[]) throws IOException
{
if(args.length!=3)
{
throw
new RuntimeException ("Syntax: java AuctionClient <name> <serverhost> <port>");
}
int port = Integer.parseInt(args[2]);
AuctionClient a =
new AuctionClient(args[0],args[1],port);
}
}
The Auction Server
import java.io.*;
import java.net.*;
import java.util.*;
public class AuctionServer
{
public AuctionServer(int port) throws IOException
{
ServerSocket server =
new ServerSocket(port);
while(true)
{
Socket client = server.accept();
DataInputStream in =
new DataInputStream(client.getInputStream());
String name = in.readUTF();
System.out.println("
New client "+name+" from " +client.getInetAddress());
BidHandler b =
new BidHandler (name, client);
b.start();
}
}
public static void main(String args[]) throws IOException
{
if(args.length != 1)
throw
new RuntimeException("Syntax: java AuctionServer <port>");
new AuctionServer(Integer.parseInt(args[0]));
}
}
The BidHandler
import java.net.*;
import java.io.*;
import java.util.*;
import java.lang.Float;
public class BidHandler extends Thread
{
Socket socket;
DataInputStream in;
DataOutputStream out;
String name;
float currentBid = 0.0f;
AuctionItem paper =
new AuctionItem(" News Paper ", " Free newspaper from 1990 ", 1.0f, false);
protected static Vector handlers =
new Vector();
public BidHandler(String name, Socket socket) throws IOException
{
this.name = name;
this.socket = socket;
in =
new DataInputStream (new BufferedInputStream (socket.getInputStream()));
out =
new DataOutputStream(new BufferedOutputStream(socket.getOutputStream()));
}
public synchronized void run()
{
try
{
broadcast("
New bidder has entered
the room");
handlers.addElement(this);
while(true)
{
broadcast(paper.getName() + paper.getDescription()+" for sale at: " +paper.getPrice());
while(paper.getStatus() == false)
{
String message = in.readUTF();
currentBid = Float.parseFloat(message);
broadcast("Bidder entered " +currentBid);
if(currentBid > paper.getPrice())
{
paper.setPrice(currentBid);
broadcast("
New Higgest Bid is "+paper.getPrice());
}
else if(currentBid < paper.getPrice())
{
broadcast("Higgest Bid is "+paper.getPrice());
}
else if(currentBid == paper.getPrice())
{
broadcast("Higgest Bid is "+paper.getPrice());
}
}
}
}
catch(IOException ex)
{
System.out.println("-- Connection to user lost.");
}
finally
{
handlers.removeElement(this);
broadcast(name+" left");
try
{
socket.close();
}
catch(IOException ex)
{
System.out.println("-- Socket to user already closed ?");
}
}
}
protected static void broadcast (String message)
{
synchronized(handlers)
{
Enumeration e = handlers.elements();
while(e.hasMoreElements())
{
BidHandler handler = (BidHandler) e.nextElement();
try
{
handler.out.writeUTF(message);
handler.out.flush();
}
catch(IOException ex)
{
handler = null;
}
}
}
}
}
The AuctionItem Class
class AuctionItem
{
String itemName;
String itemDescription;
float itemPrice;
boolean itemStatus;
//Create a
new auction item with name, description, price and status
public AuctionItem(String name, String description, float price, boolean status)
{
itemName = name;
itemDescription = description;
itemPrice = price;
itemStatus = status;
}
//return
the price of
the item.
public synchronized float getPrice()
{
return itemPrice;
}
//Set
the price of
the item.
public synchronized void setPrice(float newPrice)
{
itemPrice = newPrice;
}
//Get
the status of
the item
public synchronized boolean getStatus()
{
return itemStatus;
}
//Set
the status of
the item
public synchronized void setStatus(boolean newStatus)
{
itemStatus = newStatus;
}
//Get
the name of
the item
public String getName()
{
return itemName;
}
//Get
the description of
the item
public String getDescription()
{
return itemDescription;
}
}
There is also simple GUI to go with this that seems to be working fine. If anyone wants it will include
the GUI code.
