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Importing into VBExpress RRS feed

  • Question

  • synchronous Server Socket Example

    The following example program creates a server that receives connection requests from clients. The server is built with an asynchronous socket, so execution of the server application is not suspended while it waits for a connection from a client. The application receives a string from the client, displays the string on the console, and then echoes the string back to the client. The string from the client must contain the string "<EOF>" to signal the end of the message.

    VB

    using System;  
    using System.Net;  
    using System.Net.Sockets;  
    using System.Text;  
    using System.Threading;  

    HOW DO I IMPORT THE ABOVE "Imports"  items into VB Express...I am trying to write a VB Application to use TCP/IP sockets..?

      
    // State object for reading client data asynchronously  
    public class StateObject {  
        // Client  socket.  
        public Socket workSocket = null;  
        // Size of receive buffer.  
        public const int BufferSize = 1024;  
        // Receive buffer.  

    the rest of the code follows on from this=>=>

    Saturday, March 18, 2017 9:58 PM

All replies

  • Hi TK_ACCEL,

    Based on your descript, I not sure what is your issue. Do you mean convert the code to VB.net? if so, please refer to the following code:

    Imports System  
    Imports System.Net  
    Imports System.Net.Sockets  
    Imports System.Text  
    Imports System.Threading  
    Imports Microsoft.VisualBasic  
      
    ' State object for reading client data asynchronously  
      
    Public Class StateObject  
        ' Client  socket.  
        Public workSocket As Socket = Nothing  
        ' Size of receive buffer.  
        Public Const BufferSize As Integer = 1024  
        ' Receive buffer.  
        Public buffer(BufferSize) As Byte  
        ' Received data string.  
        Public sb As New StringBuilder  
    End Class 'StateObject  
      
    Public Class AsynchronousSocketListener  
        ' Thread signal.  
        Public Shared allDone As New ManualResetEvent(False)  
      
        ' This server waits for a connection and then uses  asychronous operations to  
        ' accept the connection, get data from the connected client,   
        ' echo that data back to the connected client.  
        ' It then disconnects from the client and waits for another client.   
        Public Shared Sub Main()  
            ' Data buffer for incoming data.  
            Dim bytes() As Byte = New [Byte](1023) {}  
      
            ' Establish the local endpoint for the socket.  
            Dim ipHostInfo As IPHostEntry = Dns.Resolve(Dns.GetHostName())  
            Dim ipAddress As IPAddress = ipHostInfo.AddressList(0)  
            Dim localEndPoint As New IPEndPoint(ipAddress, 11000)  
      
            ' Create a TCP/IP socket.  
            Dim listener As New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)  
      
            ' Bind the socket to the local endpoint and listen for incoming connections.  
            listener.Bind(localEndPoint)  
            listener.Listen(100)  
      
            While True  
                ' Set the event to nonsignaled state.  
                allDone.Reset()  
      
                ' Start an asynchronous socket to listen for connections.  
                Console.WriteLine("Waiting for a connection...")  
                listener.BeginAccept(New AsyncCallback(AddressOf AcceptCallback), listener)  
      
                ' Wait until a connection is made and processed before continuing.  
                allDone.WaitOne()  
            End While  
        End Sub 'Main  
      
        Public Shared Sub AcceptCallback(ByVal ar As IAsyncResult)  
            ' Get the socket that handles the client request.  
            Dim listener As Socket = CType(ar.AsyncState, Socket)  
            ' End the operation.  
            Dim handler As Socket = listener.EndAccept(ar)  
      
            ' Create the state object for the async receive.  
            Dim state As New StateObject  
            state.workSocket = handler  
            handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, New AsyncCallback(AddressOf ReadCallback), state)  
        End Sub 'AcceptCallback  
      
        Public Shared Sub ReadCallback(ByVal ar As IAsyncResult)  
            Dim content As String = String.Empty  
      
            ' Retrieve the state object and the handler socket  
            ' from the asynchronous state object.  
            Dim state As StateObject = CType(ar.AsyncState, StateObject)  
            Dim handler As Socket = state.workSocket  
      
            ' Read data from the client socket.   
            Dim bytesRead As Integer = handler.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))  
      
                ' Check for end-of-file tag. If it is not there, read   
                ' more data.  
                content = state.sb.ToString()  
                If content.IndexOf("<EOF>") > -1 Then  
                    ' All the data has been read from the   
                    ' client. Display it on the console.  
                    Console.WriteLine("Read {0} bytes from socket. " + vbLf + " Data : {1}", content.Length, content)  
                    ' Echo the data back to the client.  
                    Send(handler, content)  
                Else  
                    ' Not all data received. Get more.  
                    handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, New AsyncCallback(AddressOf ReadCallback), state)  
                End If  
            End If  
        End Sub 'ReadCallback  
      
        Private Shared Sub Send(ByVal handler As Socket, ByVal 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.  
            handler.BeginSend(byteData, 0, byteData.Length, 0, New AsyncCallback(AddressOf SendCallback), handler)  
        End Sub 'Send  
      
        Private Shared Sub SendCallback(ByVal ar As IAsyncResult)  
            ' Retrieve the socket from the state object.  
            Dim handler As Socket = CType(ar.AsyncState, Socket)  
      
            ' Complete sending the data to the remote device.  
            Dim bytesSent As Integer = handler.EndSend(ar)  
            Console.WriteLine("Sent {0} bytes to client.", bytesSent)  
      
            handler.Shutdown(SocketShutdown.Both)  
            handler.Close()  
            ' Signal the main thread to continue.  
            allDone.Set()  
        End Sub 'SendCallback  
    End Class 'AsynchronousSocketListener  
    

    Best regards,

    Cole Wu


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    • Proposed as answer by Cor Ligthert Monday, March 20, 2017 8:05 AM
    Monday, March 20, 2017 7:57 AM
    Moderator