VB .NET Asynchronous Client Program Example

Create a new class library project and you might want to use the solution name and project name, AsyncTcpClient as shown in the following Figure.

Imports System

Imports System.Net

Imports System.Net.Sockets

Imports System.Collections

Imports System.Threading

Imports AsyncPacketClass.AsyncPacket

' Displays simple usage information       

    Shared Sub usage()

        Console.WriteLine("Executable_file_name [-c count] [-n address] [-p port]")

        Console.WriteLine("Available options:")

        Console.WriteLine("     -c count        Number of simultaneous asynch connects (BeginAccept) to create")

        Console.WriteLine("     -n address      Server address to connect to")

        Console.WriteLine("     -p port         Port number to connect to server on")

        Console.WriteLine()

    End Sub

    ' This is the main program that parses the command line parameters and sets up each TCP

    ' listening socket by creating a TcpServer object to handle client connections to each

    ' listening endpoint. The TcpServer object creates a ClientConnection object for each

    ' established connection which handles IO operations from each client.       

    Shared Sub Main()

        Dim clientList As ArrayList = New ArrayList

        Dim clientListEmpty As ManualResetEvent = New ManualResetEvent(False)

        Dim serverName As String = "localhost"

        Dim connectCount As Integer = 5

        Dim serverPort As Integer = 5150

        ' Parse the command line

        Dim appArguments As String() = Environment.GetCommandLineArgs()

        Dim i As Integer

        usage()

        For i = 1 To appArguments.GetUpperBound(0)

            Try

                Dim CurArg() As Char = appArguments(i).ToCharArray(0, appArguments(i).Length)

                If (CurArg(0) = "-") Or (CurArg(0) = "/") Then

                    Select Case Char.ToLower(CurArg(1), System.Globalization.CultureInfo.CurrentCulture)

                        Case "c"

                            ' How many client connections to establish to server

                            i += 1

                            connectCount = System.Convert.ToInt32(appArguments(i))

                        Case "n"

                            ' Server address/name to connect to

                            i += 1

                            serverName = appArguments(i)

                        Case "p"

                            ' Port on which server is listening on

                            i += 1

                            serverPort = System.Convert.ToInt32(appArguments(i))

                        Case Else

                            usage()

                    End Select

                End If

            Catch

                usage()

                Exit Sub

            End Try

        Next

        Try

            ' Resolve the host name and create 'connectCount' number of

            '    ClientConnection objects for each address returned from

            '    name resolution.

            Console.WriteLine("Resolving the host name & creating connection count...")

            Dim resolvedHost As IPHostEntry = Dns.GetHostEntry(serverName)

            Dim addr As IPAddress

            For Each addr In resolvedHost.AddressList

                Dim serverEndPoint As IPEndPoint = New IPEndPoint(addr, serverPort)

                Dim clientConn As ClientConnection

                For i = 0 To connectCount - 1

                    clientConn = New ClientConnection(serverEndPoint, clientList, clientListEmpty)

                    Monitor.Enter(clientList)

                    clientList.Add(clientConn)

                    Monitor.Exit(clientList)

                Next

            Next

        Catch err As Exception

            Console.WriteLine("Error occurred: {0}", err.Message)

        End Try

        Try

            ' Wait until all the TCP server sockets are done

            Console.WriteLine("Waiting until all the TCP server sockets are done...")

            While (True)

                clientListEmpty.WaitOne()

                clientListEmpty.Reset()

                Console.WriteLine("Connected clients: {0}", clientList.Count)

                If (clientList.Count = 0) Then

                    Exit While

                End If

            End While

            Exit Try

        Catch err As Exception

            Console.WriteLine("Error occurred: {0}", err.Message)

        End Try

    End Sub