Connection to target machine refused:WPF window application?

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Hi Team

I have a problem with my WPF window application, basically the application is sending a request to server application(echotool.exe) which must reads the data as a json and then TCP client must be able to see this back as responce. Problem now my application when i debug is throwing this server/network connection refuse. the IP is

127.0.0.1

and port is 12345. I am using putty to telnet using this IP address and port for testing my code.

The issue gets this connection refuse to a target machine on this line when debug

await using NetworkStream stream = Client.GetStream();

No firewall or ports conflict i tested and no issue found. Could i need to implement a server code to achieve this if so please assist me.

What I have tried:

C#

//Back end

<pre>using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Sockets;
using System.Net;
using System.Text;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;


namespace PingServerApp
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

           
        }

        // declaring some local variables and method for clicking buttons.

        bool eco = false;
        async void OnClick1(object sender, RoutedEventArgs e)
        {
            // add to datagrid
            dataGrid.Items.Clear();
            await TcpRequest();
        }

       

        void OnClick2(object sender, RoutedEventArgs e)
        {
            eco = false;
        }
        class Body { public Guid Id { get; set; } }

        // class for model

        public class TCPConnectionModel
        {
            public TimeOnly Started { get; set; }
            public TimeOnly Processed { get; set; }
            public TimeSpan Elapsed { get { return Processed - Started; } set { } }
        }

        // TCPRequest for body and serialize and deserialize json data

        async Task TcpRequest()
        {
            try
            {

                // initiate tcp
                IPHostEntry IpHostInfo = Dns.GetHostEntry("127.0.0.1");
                IPAddress IpAddress = IpHostInfo.AddressList[0];

                // initiate endPoint
                var endPoint = new IPEndPoint(IpAddress, 12345);

                // starting tcp client
                using TcpClient Client = new TcpClient();
                await Client.ConnectAsync(endPoint);
                await using NetworkStream stream = Client.GetStream();
                eco = true;
                while (eco)
                {

                    // start timer
                    TCPConnectionModel displayData = new() { Started = TimeOnly.FromDateTime(DateTime.Now) };

                    // initiate send data
                    Body requestBody = new() { Id = Guid.NewGuid() };

                    //initiate recieve data
                    var buffer = new byte[1_024];

                    // Json Serialize
                    string jsonString = JsonSerializer.Serialize(requestBody);

                    // tcp send
                    await stream.WriteAsync(Encoding.ASCII.GetBytes(jsonString));

                    // tcp recieve and decode
                    int received = await stream.ReadAsync(buffer);
                    var message = Encoding.UTF8.GetString(buffer, 0, received);

                    // json Deserialize
                    Body? recievedBody = JsonSerializer.Deserialize<Body>(message);

                    // stop timer
                    displayData.Processed = TimeOnly.FromDateTime(DateTime.Now);

                    // delay for 500ms
                    Thread.Sleep(500);

                    // add to datagrid
                    dataGrid.Items.Add(displayData);

                    // display result in status bar
                    resultveiw.Text = message;
                }
            }
            catch (Exception ex)
            {
                resultveiw.Text = ex.Message;
            }
        }
    }
}

// EchoTest Server listens to 12345

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;
using System.Net.Sockets;
using SimpleTCP;
using System.IO;

namespace GUI
{
    /// <summary>
    /// Interaction logic for EchoWindowTest.xaml
    /// </summary>
    public partial class EchoWindowTest : Window
    {
        public EchoWindowTest()
        {
            InitializeComponent();
        }

        SimpleTcpServer server;


        public class DisplayData
        {
            public TimeOnly Started { get; set; }
            public TimeOnly Processed { get; set; }
            public TimeSpan Elapsed { get { return Processed - Started; } set { } }
        }
        private void MainWindow_Load(object sender, EventArgs e)
        {
            try
            {

                DisplayData displayData = new() { Started = TimeOnly.FromDateTime(DateTime.Now) };
                displayData.Processed = TimeOnly.FromDateTime(DateTime.Now);
                server = new SimpleTcpServer();
                server.Delimiter = 0 * 13;
                server.StringEncoder = Encoding.UTF8;
                server.DataReceived += Server_DataReceived;




                Thread.Sleep(500);
                dataGrid.Items.Add(displayData);



            }
            catch (Exception ex)
            {
                txtStatus.Text = ex.Message;
            }
        }
        private void Server_DataReceived(object sender, SimpleTCP.Message e)
        {
            txtStatus.Dispatcher.Invoke(new Action(delegate
            {
                txtStatus.Text += e.MessageString;

            }));
        }

        public void btnStart_Click(object sender, RoutedEventArgs e) /*Start button*/
        {
            txtStatus.Text += "Server starting ...";
            System.Net.IPAddress ip = new System.Net.IPAddress(long.Parse(txtHost.Text));
            server.Start(ip, Convert.ToInt32(txtPort.Text));



        }

        public void btnStop_Click(object sender, RoutedEventArgs e) /*Stop button*/
        {
            if (server.IsStarted)
                server.Stop();

        }



    }
}

// Front end

<Window x:Class="PingServerApp.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:PingServerApp"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Button Name="btn1" Content="Start" Click="OnClick1" ClickMode="Press" HorizontalAlignment="Left" Margin="418,10,0,0" VerticalAlignment="Top" RenderTransformOrigin="0.517,0.658" Height="55" Width="385" Background="Gold"/>
        <Button Name="btn2" Content="Stop" Click="OnClick2" ClickMode="Press" HorizontalAlignment="Left" Margin="418,70,0,0" VerticalAlignment="Top" Width="390" Height="55" Background="Aqua"/>
        <DataGrid x:Name="dataGrid" ItemsSource="{Binding TCPConnectionModel}" Margin="0,0,387,10">
            <DataGrid.Columns>
                <DataGridTextColumn Header = "Started" Binding = "{Binding Started}"/>
                <DataGridTextColumn Header = "Processed" Binding = "{Binding Processed}" />
                <DataGridTextColumn Header = "Elapsed?" Binding = "{Binding Elapsed}" />
            </DataGrid.Columns>
        </DataGrid>
        <StatusBar Margin="413,293,5,10">
            <StatusBarItem Width="380" Height="69" VerticalAlignment="Bottom" RenderTransformOrigin="0.486,0.619" Margin="0,0,0,21">
                <TextBlock Text="Nothing yet" x:Name="resultveiw"></TextBlock>
            </StatusBarItem>
        </StatusBar>
    </Grid>
</Window>

// Front end test xaml

<Window x:Class="GUI.EchoWindowTest"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:GUI"
        mc:Ignorable="d"
        Title="EchoWindowTest" Height="450" Width="800">
    <Grid>

        <Grid.Background>
            <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                <GradientStop Color="#FF39494C" Offset="0.008"/>
                <GradientStop Color="#FF39494C" Offset="1"/>
            </LinearGradientBrush>
        </Grid.Background>
        <Label Content="Host:" HorizontalAlignment="Left" Height="32" Margin="204,94,0,0" VerticalAlignment="Top" Width="62" FontSize="20" Foreground="White"/>
        <Label Content="Port:" HorizontalAlignment="Left" Margin="366,94,0,0" VerticalAlignment="Top" Height="40" Width="56" FontSize="20" Foreground="White"/>
        <DataGrid x:Name="dataGrid" ItemsSource="{Binding displayDataList}" Margin="0,0,617,0" Background="#FFDDDDDD">
            <DataGrid.Columns>
                <DataGridTextColumn Header = "Started" Binding = "{Binding Started}" />
                <DataGridTextColumn Header = "Processed" Binding = "{Binding Processed}" />
                <DataGridTextColumn Header = "Elapsed?" Binding = "{Binding Elapsed}" />
            </DataGrid.Columns>
        </DataGrid>
        <Button x:Name="btnStart" Content="Start" HorizontalAlignment="Left" Height="29" Margin="524,97,0,0" VerticalAlignment="Top" Width="97" Click="btnStart_Click"/>
        <Button x:Name="btnStop" Content="Stop" HorizontalAlignment="Left" Height="29" Margin="651,97,0,0" VerticalAlignment="Top" Width="95" Click="btnStop_Click"/>
        <TextBox x:Name="txtStatus" HorizontalAlignment="Left" Height="159" Margin="204,169,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="542" Background="#FFDDDDDD"/>
        <TextBox x:Name="txtHost" HorizontalAlignment="Left" Height="26" Margin="262,100,0,0" TextWrapping="Wrap" Text="127.0.0.1" VerticalAlignment="Top" Width="90" FontSize="20" Background="{x:Null}" Foreground="White"/>
        <TextBox x:Name="txtPort" HorizontalAlignment="Left" Height="26" Margin="418,99,0,0" TextWrapping="Wrap" Text="12345" VerticalAlignment="Top" Width="90" FontSize="20" Background="{x:Null}" Foreground="White"/>

    </Grid>
</Window>

Posted 16-Sep-22 4:21am

Gcobani Mkontwana

Updated 20-Sep-22 14:37pm

v2

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Comments

Richard MacCutchan 16-Sep-22 11:13am

You need a server listening on port 12345.

Gcobani Mkontwana 19-Sep-22 4:45am

@Richard MacCutchan can you help me how to do that based on what i have currently?

Gcobani Mkontwana 20-Sep-22 20:21pm

@Richard MacCuthan, yes i do have server but how do i make it to inherit the TCPClient to have relationship with Server?

Richard MacCutchan 21-Sep-22 4:02am

Sorry I do not understand. The server needs to be actively listening on a fixed port for connection requests. The client must try to connect to the listening port.

Gcobani Mkontwana 21-Sep-22 8:52am

@Richard MacCutchan i guess i will research and keep on trying, hopefully i wont be stuck

Richard Deeming 22-Sep-22 5:33am

IPHostEntry IpHostInfo = Dns.GetHostEntry("127.0.0.1");
IPAddress IpAddress = IpHostInfo.AddressList[0];

Why? If you want to connect to the local machine, just use IPAddress.Loopback - there's no need to perform a DNS lookup on the IP address just to get the IP address!

Gcobani Mkontwana 25-Sep-22 7:53am

@Richard MacCutchan, thanks but have you tried this on your end?

Gcobani Mkontwana 25-Sep-22 8:14am

@Richard MacCutchan i commented out the DNS.GetHostEntry and use IpAddress.Loopback am still getting connection refused to target machine.

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