Imports System
Imports System.Net
Imports System.Net.Sockets
Imports System.Threading
Imports System.Text
' State object for receiving data from remote device.
Public Class StateObject
' Client socket.
Public workSocket As Socket = Nothing
' Size of receive buffer.
Public BufferSize As Integer = 256
' Receive buffer.
Public buffer(256) As Byte
' Received data string.
Public sb As New StringBuilder()
End Class 'StateObject
Public Class AsynchronousClient
' The port number for the remote device.
Private Shared port As Integer = 11000
' ManualResetEvent instances signal completion.
Private Shared connectDone As New ManualResetEvent(False)
Private Shared sendDone As New ManualResetEvent(False)
Private Shared receiveDone As New ManualResetEvent(False)
' The response from the remote device.
Private Shared response As [String] = [String].Empty
Private Shared Sub StartClient()
' Connect to a remote device.
Try
' Establish the remote endpoint for the socket.
' The name of the
' remote device is "host.contoso.com".
Dim ipHostInfo As IPHostEntry = Dns.Resolve("host.contoso.com")
Dim ipAddress As IPAddress = ipHostInfo.AddressList(0)
Dim remoteEP As New IPEndPoint(ipAddress, port)
' Create a TCP/IP socket.
Dim client As New Socket(AddressFamily.InterNetwork, _
SocketType.Stream, ProtocolType.Tcp)
' Connect to the remote endpoint.
client.BeginConnect(remoteEP, AddressOf ConnectCallback, client)
connectDone.WaitOne()
' Send test data to the remote device.
Send(client, "This is a test<EOF>")
sendDone.WaitOne()
' Receive the response from the remote device.
Receive(client)
receiveDone.WaitOne()
' Write the response to the console.
Console.WriteLine("Response received : {0}", response)
' Release the socket.
client.Shutdown(SocketShutdown.Both)
client.Close()
Catch e As Exception
Console.WriteLine(e.ToString())
End Try
End Sub 'StartClient
Private Shared Sub ConnectCallback(ar As IAsyncResult)
Try
' Retrieve the socket from the state object.
Dim client As Socket = CType(ar.AsyncState, Socket)
' Complete the connection.
client.EndConnect(ar)
Console.WriteLine("Socket connected to {0}", _
client.RemoteEndPoint.ToString())
' Signal that the connection has been made.
connectDone.Set()
Catch e As Exception
Console.WriteLine(e.ToString())
End Try
End Sub 'ConnectCallback
Private Shared Sub Receive(client As Socket)
Try
' Create the state object.
Dim state As New StateObject()
state.workSocket = client
' Begin receiving the data from the remote device.
client.BeginReceive(state.buffer, 0, state.BufferSize, 0, _
AddressOf ReceiveCallback, state)
Catch e As Exception
Console.WriteLine(e.ToString())
End Try
End Sub 'Receive
Private Shared Sub ReceiveCallback(ar As IAsyncResult)
Try
' Retrieve the state object and client socket
' from the asynchronous state object.
Dim state As StateObject = CType(ar.AsyncState, StateObject)
Dim client As Socket = state.workSocket
' Read data from the remote device.
Dim bytesRead As Integer = client.EndReceive(ar)
If bytesRead > 0 Then
' There might be more data, so store the data received so far.
state.sb.Append(Encoding.ASCII.GetString(state.buffer, 0, _
bytesRead))
' Get the rest of the data.
client.BeginReceive(state.buffer, 0, state.BufferSize, 0, _
AddressOf ReceiveCallback, state)
Else
' All the data has arrived; put it in response.
If state.sb.Length > 1 Then
response = state.sb.ToString()
End If
' Signal that all bytes have been received.
receiveDone.Set()
End If
Catch e As Exception
Console.WriteLine(e.ToString())
End Try
End Sub 'ReceiveCallback
Private Shared Sub Send(client As Socket, data As [String])
' Convert the string data to byte data using ASCII encoding.
Dim byteData As Byte() = Encoding.ASCII.GetBytes(data)
' Begin sending the data to the remote device.
client.BeginSend(byteData, 0, byteData.Length, 0, _
AddressOf SendCallback, client)
End Sub 'Send
Private Shared Sub SendCallback(ar As IAsyncResult)
Try
' Retrieve the socket from the state object.
Dim client As Socket = CType(ar.AsyncState, Socket)
' Complete sending the data to the remote device.
Dim bytesSent As Integer = client.EndSend(ar)
Console.WriteLine("Sent {0} bytes to server.", bytesSent)
' Signal that all bytes have been sent.
sendDone.Set()
Catch e As Exception
Console.WriteLine(e.ToString())
End Try
End Sub 'SendCallback
'Entry point that delegates to C-style main Private Function.
Public Overloads Shared Sub Main()
System.Environment.ExitCode = _
Main(System.Environment.GetCommandLineArgs())
End Sub
Overloads Public Shared Function Main(args() As [String]) As Integer
StartClient()
Return 0
End Function 'Main
End Class 'AsynchronousClient
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