C# CFC Issue - The IASyncResult object was not returned from the corresponding asynchronous method o

[Yann STEPHAN via .NET 247]

I have a simple question:

Why a simple socket with IAsyncResult works fine on PC but not on Pocket PC. I have an exception given by EndReceive( ar );

Okay, I know that I can pass the socket as parameter of the IAsyncResult, but here is not the question: Why this code runs fine on PC but I have an exception on Pocket PC.

Here the code:

using System;
using System.Drawing;
using System.Collections;
using System.Windows.Forms;
using System.Data;
using System.Net.Sockets;
using System.Net;
using System.Text;


namespace TestSocket
{
/// <summary>
/// Summary description for Form1.
/// </summary>
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.TextBox ctlTxtInformation;
private System.Windows.Forms.MainMenu mainMenu1;
private System.Net.Sockets.Socket m_Socket;
private System.Net.IPEndPoint m_IPEndPoint;
private System.Net.EndPoint m_EndPoint;
private byte[] m_bBuffer = new byte[2048];
private System.Windows.Forms.Button ctlButtonExit;
private AsyncCallback m_AsyncCallback;
private ASCIIEncoding m_AsciiEncoding = new ASCIIEncoding();


public Form1()
{
//
// Required for Windows Form Designer support
//
InitializeComponent();

FillIPAddress();

m_AsyncCallback = new AsyncCallback(this.OnUDPReceive);

m_Socket = new Socket(AddressFamily.InterNetwork,SocketType.Dgram,ProtocolType.Udp );

m_IPEndPoint = new IPEndPoint(IPAddress.Parse("192.168.0.6"), 5000);
m_EndPoint = (EndPoint) m_IPEndPoint;

m_Socket.Bind(m_IPEndPoint);

m_Socket.BeginReceiveFrom(m_bBuffer, 0, m_bBuffer.Length, SocketFlags.None, ref m_EndPoint, m_AsyncCallback, this);
}
/// <summary>
/// Clean up any resources being used.
/// </summary>
protected override void Dispose( bool disposing )
{
if (m_Socket.Connected == true)
{
m_Socket.Shutdown(SocketShutdown.Both);
m_Socket.Close();
}

base.Dispose( disposing );
}
#region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
{
this.mainMenu1 = new System.Windows.Forms.MainMenu();
this.ctlTxtInformation = new System.Windows.Forms.TextBox();
this.ctlButtonExit = new System.Windows.Forms.Button();
//
// ctlTxtInformation
//
this.ctlTxtInformation.AcceptsReturn = true;
this.ctlTxtInformation.AcceptsTab = true;
this.ctlTxtInformation.BackColor = System.Drawing.Color.Black;
this.ctlTxtInformation.ForeColor = System.Drawing.Color.White;
this.ctlTxtInformation.Multiline = true;
this.ctlTxtInformation.ReadOnly = true;
this.ctlTxtInformation.Size = new System.Drawing.Size(240, 232);
this.ctlTxtInformation.Text = "==> SOCKET TEST (ASYNC METHOD)\r\n";
//
// ctlButtonExit
//
this.ctlButtonExit.Location = new System.Drawing.Point(80, 232);
this.ctlButtonExit.Size = new System.Drawing.Size(72, 40);
this.ctlButtonExit.Text = "Exit";
this.ctlButtonExit.Click += new System.EventHandler(this.ctlButtonExit_Click);
//
// Form1
//
this.Controls.Add(this.ctlButtonExit);
this.Controls.Add(this.ctlTxtInformation);
this.Menu = this.mainMenu1;
this.Text = "Form1";

}
#endregion

public void OnUDPReceive( IAsyncResult ar )
{
int nBytesRec = 0;

try
{
nBytesRec = m_Socket.EndReceive( ar );

if (nBytesRec > 0)
{
ctlTxtInformation.Text += m_AsciiEncoding.GetString(m_bBuffer, 0, nBytesRec);
}

m_Socket.BeginReceiveFrom(m_bBuffer, 0, m_bBuffer.Length, SocketFlags.None, ref m_EndPoint, m_AsyncCallback, this);
}
catch(Exception e)
{
Console.WriteLine("==> [Form1/OnUDPReceive] - Exception: " + e.Message);
}
}

private void FillIPAddress()
{
String strHostName = Dns.GetHostName();

IPHostEntry iphostentry = Dns.GetHostByName(strHostName);

if (iphostentry.AddressList.Length != 0)
{
foreach(IPAddress ipaddress in iphostentry.AddressList)
{
ctlTxtInformation.Text += "==> IP:" + ipaddress + "\r\n";
}
}
else
{
ctlTxtInformation.Text += "==> NO IP AVAILABLE" + "\r\n";;
}
}

/// <summary>
/// The main entry point for the application.
/// </summary>

static void Main()
{
try
{
Application.Run(new Form1());
}
catch(Exception exception)
{
Console.WriteLine("==> Exception: " + exception.Message);
}
}

private void ctlButtonExit_Click(object sender, System.EventArgs e)
{
this.Close();
}
}
}

 

[Jon Skeet [C# MVP]]

I have a simple question:

Why a simple socket with IAsyncResult works fine on PC but not on
Pocket PC. I have an exception given by EndReceive( ar );

Okay, I know that I can pass the socket as parameter of the
IAsyncResult, but here is not the question: Why this code runs fine
on PC but I have an exception on Pocket PC.

I'm not sure why it runs on a PC at all - shouldn't you be calling
EndReceiveFrom rather than EndReceive? I would have thought that would
be the cause of the problem rather than using the wrong socket.

 

[yogendrasinh]

When frequently Open/Close UDP sockets, above exception comes while closing one socket and start listening on another socket on the same port. OnReceive method is called (only once) for the previous (closed) socket while doing “Start Listening” on new socket on the same port. As old socket is already dereferenced and closed, you will get above socket exception on EndReceiveFrom or EndReceive method.

In short, you have to ignore the calls of your OnReceive (or similar) for Old socket which you no longer use i.e. closed sockets.

refer: http://rajputyh.blogspot.com/2010/04/solve-exception-message-iasyncresult.html

code block:

 private void OnReceive(IAsyncResult ar)
 {
 	  if (ar == currentAynchResult)
 	  {
 		 //process further
 	  }
 	  else
 	  {
 		 //Ignore
 	  }
 	  BeginReceive();
 }