Date: 28 Sep 2001 01:36:26 -0700
From: tristan.braun@gmx.net (NuArb)
Subject: IO::Socket && IO::Select Problem
Message-Id: <3dae1176.0109280036.b6a7d90@posting.google.com>

Hi all socket-developers,

I tried to write a chat application. My client is a Java Applet and
the server is written in
PERL.

The server is listening via IO::Socket on Port 2666. The server is
blocking until someone
has something to say or a new connection request. New requests will be
accepted and added to
IO::Select.

The client tries to connect to the server and is starting a thread for
listening on the socket.

Both the java and the perl code works well with some (~10) WS opening
the applet and I thougth
it is on the time to stress the server. I created a MDI VB project and
added a form with the
InternetExplorer Control on it. Per default the Control navigates to
my applet.

I instanciated the page 30 times and the last instance could send a
message. The same with 60.

When I try 90 simultanious connections the connect sucedded for all.
ALL can receive messages.
BUT only the first ~60 Instances can send and the server receives the
message. After closing
any Instances the previously sended message will received by the
server.

The same result is when I startet the VB MDI on two NT boxes with each
have 50 instances.

And when try more than 127 connections + 1 listen my perlserver
crashes.

But in the worst case I will have ~800 users connecting to it !

Here is a snipet of the log I am generating:

IP [fileno]: Message [IO::Select->Count()]

 ...
10.84.39.163[43]: Hello
10.84.39.163[67]: This is a test
10.84.39.163[5]: disconnected [121]
10.84.39.163[6]: disconnected [120]
10.84.39.163[7]: disconnected [119]
10.84.39.163[8]: disconnected [118]
10.84.39.163[9]: disconnected [117]
10.84.39.163[71]: Some other stuff sended previously
10.84.39.163[10]: disconnected [116]
10.84.39.163[11]: disconnected [115]
10.84.39.163[12]: disconnected [114]
10.84.39.163[13]: disconnected [113]
10.84.39.163[14]: disconnected [112]
10.84.39.163[72]: Some other stuff sended previously
10.84.39.163[74]: Some other stuff sended previously
10.84.39.163[75]: Whats up ?
 ...

With netstat -a I receive the following lines:

 The client:
  TCP    myClient:3292         0.0.0.0:0              LISTENING
  ...
  TCP    myClient:3411         0.0.0.0:0              LISTENING

  TCP    myClient:3292         myServer:2666          ESTABLISHED
  ...
  TCP    myClient:3411         myServer:2666          ESTABLISHED

The server:
  TCP    myServer:2666         myClient:3292          ESTABLISHED
  ...
  TCP    myServer:2666         myClient:3411          ESTABLISHED

Here is the server:
- Perl v5.6.1 Binary build 628 provided by ActiveState
- Windows 2000 Server with IIS 5.0

<perl>
use strict;
use IO::Socket;
use IO::Socket::INET;
use IO::Select;
use FileHandle;

my $CHAT = new FileHandle;

$SIG{"INT"} = sub { $CHAT->close; exit 0 };

# Listen-Socket erstellen, das auf eingehende Verbindungen wartet.
my $listen = IO::Socket::INET->new(Proto => 'tcp',
				   LocalPort => 2666,
				   Listen => 256,
				   Reuse => 1) or die $!;

# Listen-Socket in die Select-Tasche stecken, die Anforderungen
überwacht.
my $select = IO::Select->new($listen);

$CHAT->open(">>Chat.txt") || die "Kann die Protokolldatei nicht
öffnen. $!\n";
$CHAT->autoflush;
my @ready;
my @lines;
my %Colors = ();
my %IP = ();
sub cCol {
	return (substr("000" . (int(rand 170) + 30) ,-3))
}

sub Debug {
	my($Text) = @_;
	print $Text;
	print $CHAT $Text;
}

# Warten bis was passiert.
while(@ready = $select->can_read) {

    my $socket;

    for $socket (@ready) {

		# Neue Sockets binden.
		if($socket == $listen) {
			my $new = $listen->accept;
			$select->add($new) if $new;
			$new->send("000000000Willkommen\n" . join('',@lines));
			$IP{$new->fileno} = join('.',unpack("CCCC", $new->peeraddr()));
			Debug ($IP{$new->fileno} . "[" . $new->fileno . "]: connected [" .
$select->count() ."]\n");
			if (not exists $Colors{$IP{$new->fileno}}) 
			{
				$Colors{$IP{$new->fileno}} = cCol . cCol . cCol;
			}
		} else {
			# Nachricht vom Socket auslesen. Wenn nicht klappt, Socket
schliessen.
			my $line="";
			$socket->recv($line,200);
			if($line eq "") 
			{
				Debug ($IP{$socket->fileno} . "[" . $socket->fileno . "]:
disconnected [" . $select->count() ."]\n"); #$socket->fileno . ":
disconnected\n";
				delete $IP{$socket->fileno};
				$select->remove($socket);
				$socket->close;
			} else {
				Debug ($IP{$socket->fileno} . "[" . $socket->fileno . "]: " .
$line);
				$line = $Colors{$IP{$socket->fileno}} . $line;
				push @lines, $line;
				shift @lines if $#lines > 5;

				my $socket;

				# Nachricht an jeden senden. Wenns nicht klappt, Socket
schliessen.
				for $socket ($select->handles) 
				{
					next if($socket==$listen);
					$socket->send("$line") or do 
					{
						print $socket->fileno . ": disconnected\n";		
						$select->remove($socket);
						$socket->close;
					};
				}
			};
		}
	}
}
1;
</perl>

Here is the client:
- Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.1_01)
- Windows NT 4.0 SP 6a

<java>
import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;
import java.io.*;
import java.net.*;

public class hello extends java.applet.Applet
{
	Font f = new Font("Tahoma", Font.BOLD,11);
	Socket socket = null;
	InputStreamReader isr = null;
	BufferedReader in = null;
	PrintWriter out = null;
	static int iWSize = 7;
	static int iSSize = 100;
	Speicher X = new Speicher(iSSize, iWSize);
	Label lblEingabe = new Label("Message :", Label.LEFT);
	TextField txtEingabe = new TextField(25);
	Button btnSend = new Button("Send");
	Color back = new Color(255,255,240);
	Scrollbar sbv = new Scrollbar();
	Scrollbar sbh = new Scrollbar(Scrollbar.HORIZONTAL,0,25,0,100);

	AdjustmentListener scroll = new AdjustmentListener()
	{
		public void adjustmentValueChanged(AdjustmentEvent e)
		{ repaint(); }
	};

	ActionListener sender = new ActionListener()
	{
		public void actionPerformed(ActionEvent e)
		{
			String sValue = new String(txtEingabe.getText());
			if (sValue != "")
			{
				out.println(sValue);
				out.flush();
				txtEingabe.setText("");
				repaint();
			}
		}
	};

	Thread checker = new Thread()
	{
		public void run()
		{
			boolean OK = true;
			while (OK)
			{
				try
				{
					String Input;
					Input = in.readLine();
					if (Input != null)
					{
						X.Add(Input);
						if (X.Count() > iWSize && X.Count() <= (iSSize - iWSize))
						{
							sbv.setVisibleAmount(100 - X.Count() + iWSize);
							sbv.setValue(sbv.getValue() + 1);
						}
						repaint();
					}
				}
				catch (Exception e)
				{
					X.Add(e.getMessage());
					OK = false;
					try
					{
						socket.close();
					}
					catch (IOException ee)
					{
						X.Add(ee.getMessage());
					}
				}
			}
		}
	};

	public void init()
	{
		setLayout(null);
		setBackground(back);
		setFont(f);

		lblEingabe.setBounds(5,5,60,20);
		add(lblEingabe);

		txtEingabe.addActionListener(sender);
		txtEingabe.setBounds(65,5,210,20);
		add(txtEingabe);

		btnSend.addActionListener(sender);
		btnSend.setBounds(280,5,60,20);
		add(btnSend);

		sbv.addAdjustmentListener(scroll);
		sbv.setBounds(330,25,10,115);
		sbv.setVisibleAmount(100);
		add(sbv);

		sbh.addAdjustmentListener(scroll);
		sbh.setBounds(5,140,325,10);
		add(sbh);

		try
		{
			socket = new Socket(getDocumentBase().getHost(),2666);
			isr = new InputStreamReader(socket.getInputStream());
			in = new BufferedReader(isr);
			out = new PrintWriter(socket.getOutputStream(), true);

			checker.start();
		}
		catch (IOException e)
		{
			X.Add(e.getMessage());
		}
		catch (SecurityException se)  
		{
			X.Add(se.getMessage());
		}
	}

	public void paint(Graphics screen)
	{
		screen.setFont(f);
		X.Rewind(iWSize + (iSSize - sbv.getVisibleAmount() -
sbv.getValue()));
		int i = 0;

		do
		{
			screen.setColor(X.Col());
			screen.drawString(X.Get(sbh.getValue()), 5, 40 + 15 * i++);
		}
		while (X.Next());
	}

	public void stop()
	{
		try
		{
			socket.close();
		}
		catch (IOException ee)
		{
			X.Add(ee.getMessage());
			repaint();
		}
	}

	class Speicher
	{
	//This is only the interface of a class simular to a stack 
		public Color Col()
		public Speicher(int SSize, int VSize)
		public void Add(String Text)
		public String Get(int iStart)
		public int Count()
		public int getCursor()
		public int Pos()
		public void Rewind(int Laenge)
		public boolean Next()
	};
};
</java>

At least the VB MDI:
- Visual Basic 6.0 (SP4)
- Windows NT 4.0 SP 6a

<vb>
Private Declare Sub Sleep Lib "kernel32" (ByVal dwMilliseconds As
Long)

Private Sub MDIForm_Activate()
    Dim x(1 To 60) As Form1
    Dim a As Integer
    Dim b As Integer

    For a = 1 To 60
        Set x(a) = New Form1
        x(a).Left = ((a - 1) Mod 3) * 4400
        x(a).Top = Round((a - 2) / 3, 0) * 3100
        x(a).Show
        x(a).WebBrowser1.Navigate "http://myServer/Java/Applet.htm"
        DoEvents
        Sleep 100
        DoEvents
    Next
End Sub

</vb>

Thanks in advance !

Regards,

Tristan