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Chapter 3 Part 4:

Threading and the Asynchronous Pattern

 

 

What do we have in this chapter 3 Part 4?

  1. VB .NET WinForm Program Example

 

VB .NET WinForm Program Example

 

Create a new Windows Forms Application project. You can use the project and solution name as shown in the following snapshot.

 

VB .NET WinForm Program Example - new Windows Forms Application project creation

 

Drag, drop and rearrange the Windows controls as shown in the following Figure. Use the information in the following Table for the controls properties.

 

Control

Property

Value

Form1

Text

WinNetworkIOCS

Button

Text

Connect, Send, Close

 

Name

ConnectButton

Label1

Text

IP Address:

TextBox1

Name

IPAddressBox

 

Text

127.0.0.1

Label2

Text

Port:

TextBox2

Name

PortBox

 

Text

5150

Label3

Text

Message to send:

TextBox3

Name

SendMessageBox

 

Text

This is a test message…

 

Multiline

True

 

VB .NET WinForm Program Example - arranging controls on the Windows Form

 

VB .NET WinForm Program Example - Invoking the Properties of the controls

 

VB .NET WinForm Program Example - Customizing the control properties

 

Drag and drop the StatusStrip control at the bottom of the Form. Then, add a StatusLabel for the StatusStrip.

 

VB .NET WinForm Program Example - Setting the StatusStrip as StatusLabel component

 

 

 

 

Next, select the StatusStrip component > Right click mouse > Select Edit Items context menu to customize the StatusLabel.

 

VB .NET WinForm Program Example - editing the StatusStrip component

 

Select the StatusLabel in the Members: pane. Change the Text value to None and the Name value to StatusBar. Close the Items Collection Editor.

 

VB .NET WinForm Program Example - customizing the StatusLabel control

 

The following is our final Windows form design.

 

VB .NET WinForm Program Example - a completed Windows Forms design

 

Double click the top button and add the following Imports directives and codes that follow.

 

Imports System.Net

Imports System.Net.Sockets

Imports System.Threading

Imports System.IO

 

    Private Sub ConnectButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ConnectButton.Click

        DisableFields()

        DoNetworkingConnection()

    End Sub

 

VB .NET WinForm Program Example - adding the click button event subroutine

 

Add more codes, DisableFields() and EnableFields() sub routines.

 

    Private Sub DisableFields()

        PortBox.Enabled = False

        IPAddressBox.Enabled = False

        SendMessageBox.Enabled = False

        ConnectButton.Enabled = False

    End Sub

 

    Private Sub EnableFields()

        PortBox.Enabled = True

        IPAddressBox.Enabled = True

        SendMessageBox.Enabled = True

        ConnectButton.Enabled = True

    End Sub

 

Add codes for writing messages to the status bar.

 

Public Delegate Sub StatusBarWriterDelegateMethod(ByVal Message As String)

 

    Private Sub WriteToStatusBar(ByVal Message As String)

        Dim SB As StatusBarWriterDelegateMethod = New StatusBarWriterDelegateMethod(AddressOf StatusBarWriter)

        SB.Invoke(Message)

    End Sub

 

    Public Sub StatusBarWriter(ByVal MessageToWrite As String)

        EnableFields()

        Me.StatusBar.Text = MessageToWrite

End Sub

 

Next, add codes for the networking part.

 

Private Sub DoNetworkingConnection()

        Dim MyThread As Thread = Nothing

 

        Try

            Dim ThreadMethod As ThreadStart = New ThreadStart(AddressOf ConnectTo)

 

            MyThread = New Thread(ThreadMethod)

 

        Catch e As Exception

            WriteToStatusBar("Failed to create thread with error: " + e.Message)

            Exit Sub

        End Try

 

        Try

            MyThread.Start()

        Catch e As Exception

            WriteToStatusBar("The thread failed to start with error: " + e.Message)

        End Try

End Sub

 

Then add codes for connection part.

 

Private Sub ConnectTo()

        Dim ServerName As String = Me.IPAddressBox.Text

        Dim Port As Integer = System.Convert.ToInt32(Me.PortBox.Text)

 

        Dim ClientSocket As Socket = Nothing

 

        Try

            ' Let's connect to a listening server

            Try

                ClientSocket = New Socket(AddressFamily.InterNetwork, _

                    SocketType.Stream, ProtocolType.IP)

 

            Catch e As Exception

                Throw New Exception("Failed to create client Socket: " + e.Message)

            End Try

 

            Dim ServerEndPoint As IPEndPoint = New IPEndPoint( _

                IPAddress.Parse(ServerName), Convert.ToInt16(Port))

 

            Try

                ClientSocket.Connect(ServerEndPoint)

 

            Catch e As Exception

                Throw New Exception("Failed to connect client Socket: " + e.Message)

            End Try

 

        Catch e As Exception

            WriteToStatusBar(e.Message)

 

            ClientSocket.Close()

            Exit Sub

        End Try

 

        ' Let's create a network stream to communicate over the connected Socket.

        Dim ClientNetworkStream As NetworkStream = Nothing

 

        Try

            Try

                ' Setup a network stream on the client Socket

                ClientNetworkStream = New NetworkStream(ClientSocket, True)

 

            Catch e As Exception

                ' We have to close the client socket here because the network

                ' stream did not take ownership of the socket.

                ClientSocket.Close()

                Throw New Exception("Failed to create a NetworkStream with error: " _

                    + e.Message)

            End Try

 

            Dim ClientNetworkStreamWriter As StreamWriter = Nothing

 

            Try

                ' Setup a Stream Writer

                ClientNetworkStreamWriter = New StreamWriter(ClientNetworkStream)

 

            Catch e As Exception

                ClientNetworkStream.Close()

                Throw New Exception("Failed to create a StreamWriter with error: " _

                    + e.Message)

            End Try

 

            Try

                ClientNetworkStreamWriter.Write(Me.SendMessageBox.Text.ToString())

 

                ClientNetworkStreamWriter.Flush()

 

                WriteToStatusBar("We wrote " + Me.SendMessageBox.Text.Length.ToString() _

                    + " character(s) to the server.")

 

            Catch e As Exception

                Throw New Exception("Failed to write to client NetworkStream with error: " _

                    + e.Message)

            End Try

 

        Catch e As Exception

            WriteToStatusBar(e.Message)

 

        Finally

            ' Close the network stream once everything is done

            ClientNetworkStream.Close()

        End Try

End Sub

 

Finally, add code for the form loading.

 

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs)

Handles MyBase.Load

End Sub

 

Build and run the project.

 

VB .NET WinForm Program Example - Windows form in action!

 

The following snapshot is a sample output. The receiver is waiting for a connection.

 

VB .NET WinForm Program Example - running the receiver/server program and start listening for connection

 

In order to see the real activities, we will test this client together with the previously created stream server/receiver program (NetworkStreamSampleCSReceiver.exe or NetworkStreamSampleVBReceiver.exe). In this case we test both programs on the same local host and you may want to test it on different hosts which mean run the receiver on host A and run the sender on host B and change the IP address of the sender accordingly.

 

Running both, the receiver and the sender programs. Firstly run the previous receiver program (NetworkStreamSampleCSReceiver.exe). The receiver is waiting a connection from sender.

Then, run the sender/client program (WinForm application). The following is a sample output for both the sender and the receiver.

 

VB .NET WinForm Program Example - running the Windows Form sender program. The action can be seen in the receiver program.

 

 

 

 

A complete code for this part is given below.

 

Imports System.Net

Imports System.Net.Sockets

Imports System.Threading

Imports System.IO

 

Public Class Form1

 

    Private Sub ConnectButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ConnectButton.Click

        DisableFields()

        DoNetworkingConnection()

    End Sub

    Private Sub DisableFields()

        PortBox.Enabled = False

        IPAddressBox.Enabled = False

        SendMessageBox.Enabled = False

        ConnectButton.Enabled = False

    End Sub

 

    Private Sub EnableFields()

        PortBox.Enabled = True

        IPAddressBox.Enabled = True

        SendMessageBox.Enabled = True

        ConnectButton.Enabled = True

    End Sub

    Public Delegate Sub StatusBarWriterDelegateMethod(ByVal Message As String)

 

    Private Sub WriteToStatusBar(ByVal Message As String)

        Dim SB As StatusBarWriterDelegateMethod = New StatusBarWriterDelegateMethod(AddressOf StatusBarWriter)

        SB.Invoke(Message)

    End Sub

 

    Public Sub StatusBarWriter(ByVal MessageToWrite As String)

        EnableFields()

        Me.StatusBar.Text = MessageToWrite

    End Sub

 

    Private Sub DoNetworkingConnection()

        Dim MyThread As Thread = Nothing

 

        Try

            Dim ThreadMethod As ThreadStart = New ThreadStart(AddressOf ConnectTo)

 

            MyThread = New Thread(ThreadMethod)

 

        Catch e As Exception

            WriteToStatusBar("Failed to create thread with error: " + e.Message)

            Exit Sub

        End Try

 

        Try

            MyThread.Start()

 

        Catch e As Exception

            WriteToStatusBar("The thread failed to start with error: " + e.Message)

        End Try

    End Sub

 

    Private Sub ConnectTo()

        Dim ServerName As String = Me.IPAddressBox.Text

        Dim Port As Integer = System.Convert.ToInt32(Me.PortBox.Text)

 

        Dim ClientSocket As Socket = Nothing

 

        Try

            ' Let's connect to a listening server

            Try

                ClientSocket = New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP)

 

            Catch e As Exception

                Throw New Exception("Failed to create client Socket: " + e.Message)

            End Try

 

            Dim ServerEndPoint As IPEndPoint = New IPEndPoint( _

                IPAddress.Parse(ServerName), Convert.ToInt16(Port))

 

            Try

                ClientSocket.Connect(ServerEndPoint)

 

            Catch e As Exception

                Throw New Exception("Failed to connect client Socket: " + e.Message)

            End Try

 

        Catch e As Exception

            WriteToStatusBar(e.Message)

 

            ClientSocket.Close()

            Exit Sub

        End Try

 

        ' Let's create a network stream to communicate over the connected Socket.

        Dim ClientNetworkStream As NetworkStream = Nothing

 

        Try

            Try

                ' Setup a network stream on the client Socket

                ClientNetworkStream = New NetworkStream(ClientSocket, True)

 

            Catch e As Exception

                ' We have to close the client socket here because the network

                ' stream did not take ownership of the socket.

                ClientSocket.Close()

                Throw New Exception("Failed to create a NetworkStream with error: "  + e.Message)

            End Try

 

            Dim ClientNetworkStreamWriter As StreamWriter = Nothing

 

            Try

                ' Setup a Stream Writer

                ClientNetworkStreamWriter = New StreamWriter(ClientNetworkStream)

 

            Catch e As Exception

                ClientNetworkStream.Close()

                Throw New Exception("Failed to create a StreamWriter with error: " + e.Message)

            End Try

 

            Try

                ClientNetworkStreamWriter.Write(Me.SendMessageBox.Text.ToString())

 

                ClientNetworkStreamWriter.Flush()

 

                WriteToStatusBar("We wrote " + Me.SendMessageBox.Text.Length.ToString()  + " character(s) to the server.")

 

            Catch e As Exception

                Throw New Exception("Failed to write to client NetworkStream with error: " + e.Message)

            End Try

 

        Catch e As Exception

            WriteToStatusBar(e.Message)

 

        Finally

            ' Close the network stream once everything is done

            ClientNetworkStream.Close()

        End Try

    End Sub

 

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs)

      Handles MyBase.Load

    End Sub

End Class

 

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