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8.2

C# asynchronous socket client

Asked by dspradling in C# Programming Language

Tags: C#

I am trying to understand and develop a client that can communicate with a hardware system over TCP/IP.  I found an article on a basic client here (http://www.java2s.com/Code/CSharp/Network/AsyncTcpClient.htm) and modified the code slightly to test with.  I can connect to the hardware and return a response to verify that it is communicating but when I send a command it does not respond and throws an ObjectDisposedException in ReceiveData block when the disconnect button is clicked.    I assume it is waiting for the hardware to return data but I'm not sure why it isn't receiving.   I am able to connect and send commands with a simple console app. 
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using System;
using System.Drawing;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Windows.Forms;
 
 
public class AsyncTcpClient : Form
{
    private TextBox newText;
    private TextBox conStatus;
    private ListBox results;
    private Socket client;
    private byte[] data = new byte[1024];
    private int size = 1024;
 
    public AsyncTcpClient()
    {
        Text = "Asynchronous TCP Client";
        Size = new Size(400, 380);
 
        Label label1 = new Label();
        label1.Parent = this;
        label1.Text = "Enter text string:";
        label1.AutoSize = true;
        label1.Location = new Point(10, 30);
 
        newText = new TextBox();
        newText.Parent = this;
        newText.Size = new Size(200, 2 * Font.Height);
        newText.Location = new Point(10, 55);
 
        results = new ListBox();
        results.Parent = this;
        results.Location = new Point(10, 85);
        results.Size = new Size(360, 18 * Font.Height);
 
        Label label2 = new Label();
        label2.Parent = this;
        label2.Text = "Connection Status:";
        label2.AutoSize = true;
        label2.Location = new Point(10, 330);
 
        conStatus = new TextBox();
        conStatus.Parent = this;
        conStatus.Text = "Disconnected";
        conStatus.Size = new Size(200, 2 * Font.Height);
        conStatus.Location = new Point(110, 325);
 
        Button sendit = new Button();
        sendit.Parent = this;
        sendit.Text = "Send";
        sendit.Location = new Point(220, 52);
        sendit.Size = new Size(5 * Font.Height, 2 * Font.Height);
        sendit.Click += new EventHandler(ButtonSendOnClick);
 
        Button connect = new Button();
        connect.Parent = this;
        connect.Text = "Connect";
        connect.Location = new Point(295, 20);
        connect.Size = new Size(6 * Font.Height, 2 * Font.Height);
        connect.Click += new EventHandler(ButtonConnectOnClick);
 
        Button discon = new Button();
        discon.Parent = this;
        discon.Text = "Disconnect";
        discon.Location = new Point(295, 52);
        discon.Size = new Size(6 * Font.Height, 2 * Font.Height);
        discon.Click += new EventHandler(ButtonDisconOnClick);
    }
 
    void ButtonConnectOnClick(object obj, EventArgs ea)
    {
        conStatus.Text = "Connecting...";
        Socket newsock = new Socket(AddressFamily.InterNetwork,
                              SocketType.Stream, ProtocolType.Tcp);
        IPEndPoint iep = new IPEndPoint(IPAddress.Parse("10.5.48.225"), 4000);
        newsock.BeginConnect(iep, new AsyncCallback(Connected), newsock);
    }
 
    void ButtonSendOnClick(object obj, EventArgs ea)
    {
        byte[] message = Encoding.ASCII.GetBytes(newText.Text);
        client.BeginSend(message, 0, message.Length, SocketFlags.None, new AsyncCallback(SendData), client);
        newText.Clear();
    }
 
    void ButtonDisconOnClick(object obj, EventArgs ea)
    {
        client.Close();
        conStatus.Text = "Disconnected";
    }
 
    void Connected(IAsyncResult iar)
    {
        client = (Socket)iar.AsyncState;
        try
        {
            this.BeginInvoke(
                (MethodInvoker)delegate()
                {
                    client.EndConnect(iar);
                    conStatus.Text = "Connected to: " + client.RemoteEndPoint.ToString();
                    client.BeginReceive(data, 0, size, SocketFlags.None,
                                  new AsyncCallback(ReceiveData), client);
                });
        }
        catch (SocketException)
        {
            conStatus.Text = "Error connecting";
        }
    }
 
    void ReceiveData(IAsyncResult iar)
    {
        this.BeginInvoke(
            (MethodInvoker)delegate()
            {
                Socket remote = (Socket)iar.AsyncState;
                int recv = remote.EndReceive(iar);
                string stringData = Encoding.ASCII.GetString(data, 0, recv);
                results.Items.Add(stringData);
            });
    }
 
    void SendData(IAsyncResult iar)
    {
        Socket remote = (Socket)iar.AsyncState;
        int sent = remote.EndSend(iar);
        remote.BeginReceive(data, 0, size, SocketFlags.None, new AsyncCallback(ReceiveData), remote);
    }
 
    public static void Main()
    {
        Application.Run(new AsyncTcpClient());
    }
}
[+][-]05/22/09 10:48 AM, ID: 24453450Expert Comment

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[+][-]05/24/09 03:56 PM, ID: 24463387Author Comment

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[+][-]05/25/09 10:53 AM, ID: 24467772Accepted Solution

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About this solution

Zone: C# Programming Language
Tags: C#
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Solution Provided By: dspradling
Participating Experts: 1
Solution Grade: A
 
 
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