VB .NET TcpListener Program Example

Create a new class library project and you might want to use TcpListenertSampleVB as the name.

Imports System

Imports System.Net

Imports System.Net.Sockets

' Displays simple usage information.

    Shared Sub usage()

        Console.WriteLine("Usage: TcpListenerSampleVB [-l address] [-p port] [-x size]")

        Console.WriteLine()

        Console.WriteLine("Available options:")

        Console.WriteLine("     -l address      Local address for TCP server to listen on")

        Console.WriteLine("     -p port         Local port for TCP server to listen on")

        Console.WriteLine("     -x size         Size of send and receive buffers")

        Console.WriteLine()

    End Sub

    ' <param name="args">Command line arguments</param>

    Shared Sub Main()

        Dim listenInterface As IPAddress = IPAddress.Any

        Dim listenPort As Short = 5150

        Dim bufferSize As Integer = 4096

        Dim i As Integer

        ' Parse the command line

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

        usage()

        For i = 1 To args.GetUpperBound(0) - 1

            Try

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

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

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

                        Case "l"        ' Local interface server should listen on

                            i = i + 1

                            listenInterface = IPAddress.Parse(args(i))

                        Case "p"        ' Port number for the destination

                            i = i + 1

                            listenPort = System.Convert.ToInt16(args(i))

                        Case "x"        ' Size of the send and receive buffers

                            i = i + 1

                            bufferSize = System.Convert.ToInt32(args(i))

                        Case Else

                            usage()

                            Exit Sub

                    End Select

                End If

            Catch e As Exception

                usage()

                Exit Sub

            End Try

        Next

        Dim tcpServer As TcpListener = Nothing

        Dim tcpClient As tcpClient = Nothing

        Dim tcpStream As NetworkStream = Nothing

        Dim sendBuffer(bufferSize) As Byte

        Dim receiveBuffer(bufferSize) As Byte

        Dim byteCount() As Byte

        Dim bytesToRead As Integer = 0

        Dim nextReadCount, rc As Integer

        ' Initialize the send buffer

        Console.WriteLine("Initializing the send buffer...")

        For i = 0 To sendBuffer.Length - 1

            sendBuffer(i) = CByte(65)

        Next

        Try

            ' Create the TCP server

            Console.WriteLine("Creating the TCP server...")

            tcpServer = New TcpListener(listenInterface, listenPort)

            Console.WriteLine("TcpListener created on address {0} and port {1}", _

                listenInterface.ToString(), _

                listenPort.ToString() _

                )

            ' Start listening for connections

            Console.WriteLine("Start listening for connections...")

            tcpServer.Start()

            ' Wait for a client connection

            Console.WriteLine("Waiting for a client connection...")

            tcpClient = tcpServer.AcceptTcpClient()

            ' Get the NetworkStream so we can do Read and Write on the client connection

            Console.WriteLine("Getting the NetworkStream for Reading and Writing on the client connection...")

            tcpStream = tcpClient.GetStream()

            byteCount = BitConverter.GetBytes(bytesToRead)

            ' First read the number of bytes the client is sending

            Console.WriteLine("Reading the number of bytes the client is sending...")

            tcpStream.Read(byteCount, 0, byteCount.Length)

            bytesToRead = BitConverter.ToInt32(byteCount, 0)

            ' Receive the data

            Console.WriteLine("Receive, Read & display data...")

            While (bytesToRead > 0)

                ' Make sure we don't read beyond what the first message indicates

                '    This is important if the client is sending multiple "messages" --

                '    but in this sample it sends only one

                If (bytesToRead < receiveBuffer.Length) Then

                    nextReadCount = bytesToRead

                Else

                    nextReadCount = receiveBuffer.Length

                End If

                ' Read some data

                rc = tcpStream.Read(receiveBuffer, 0, nextReadCount)

                ' Display what we read

                Dim readText As String = System.Text.Encoding.ASCII.GetString(receiveBuffer, 0, rc)

                Console.WriteLine("Received: {0}", readText)

                bytesToRead -= rc

            End While

            ' First send the number of bytes the server is responding with

            Console.WriteLine("Sending the number of bytes the server is responding with...")

            byteCount = BitConverter.GetBytes(sendBuffer.Length)

            tcpStream.Write(byteCount, 0, byteCount.Length)

            ' Send the actual data

            Console.WriteLine("Send the actual data...")

            tcpStream.Write(sendBuffer, 0, sendBuffer.Length)

            ' Close up the client

            Console.WriteLine("Closing up the client...")

            tcpStream.Close()

            tcpStream = Nothing

            tcpClient.Close()

            tcpClient = Nothing

        Catch err As SocketException

            ' Exceptions on the TcpListener are caught here

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

        Catch err As System.IO.IOException

            ' Exceptions on the NetworkStream are caught here

            Console.WriteLine("I/O error: {0}", err.Message)

        Finally

            ' Close any remaining open resources

            Console.WriteLine("Closing any remaining open resources...")

            If (Not IsNothing(tcpServer)) Then

                tcpServer.Stop()

            End If

            If (Not IsNothing(tcpStream)) Then

                tcpStream.Close()

            End If

            If (Not IsNothing(tcpClient)) Then

                tcpClient.Close()

            End If

        End Try

    End Sub

// TcpClientSampleCP.cpp : main project file.

#include "stdafx.h"

using namespace System;

using namespace System::Net;

using namespace System::Net::Sockets;

/// <summary>

/// Displays simple usage information.

/// </summary>

static void usage()

{

    Console::WriteLine("Usage: TcpClientSample.exe [-n server] [-p port] [-x size]");

    Console::WriteLine("Available options:");

    Console::WriteLine("     -n server       Name or address of server to connect to");

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

    Console::WriteLine("     -x size         Size of send and receive buffers");

    Console::WriteLine();

}

int main(array<System::String ^> ^args)

{

    // Initial/default values

    String^ serverAddress = "localhost";

    unsigned short serverPort = 5150;

    int bufferSize = 1024;

    // Parse the command line

    if(args->Length != 0)

    {

    for (int i = 0; i < args->Length; i++)

    {

        try

        {

            if ((args[i][0] == '-') || (args[i][0] == '/'))

            {

                switch (Char::ToLower(args[i][1]))

                {

                    case 'n':       // String name or address of server to connect to

                        serverAddress = args[++i];

                        break;

                    case 'p':       // Port number for the destination

                        serverPort = Convert::ToUInt16(args[++i]);

                        break;

                    case 'x':       // Size of the send and receive buffers

                        bufferSize = Convert::ToInt32(args[++i]);

                        break;

                    default:

                        usage();

                        return 0;

                }

            }

        }

        catch(Exception^ err)

        {

            Console::WriteLine("TCP client: Error - {0}", err->Message);

            usage();

            return 0;

        }

    }

}

else

{

     usage();

     return 0;

}

    TcpClient^ simpleTcp = nullptr;

    NetworkStream^ tcpStream = nullptr;

    array<Byte>^ sendBuffer = gcnew array<Byte>(bufferSize);

    array<Byte>^ receiveBuffer = gcnew array<Byte>(bufferSize);

    array<Byte>^ byteCount;

    int bytesToRead = 0, nextReadCount, rc;

    // Initialize the send buffer

    Console::WriteLine("TCP client: Initializing the send buffer...");

    for (int i = 0; i < sendBuffer->Length; i++)

        sendBuffer[i] = (Byte)'X';

    try

    {

        // Create the client and indicate the server to connect to

        Console::WriteLine("TCP client: Creating the client and indicate the server to connect to...");

        simpleTcp = gcnew TcpClient(serverAddress, (int)serverPort);

        // Retrieve the NetworkStream so we can do Read and Write

        Console::WriteLine("TCP client: Retrieving the NetworkStream so we can do Read and Write...");

        tcpStream = simpleTcp->GetStream();

        // First send the number of bytes the client is sending

        Console::WriteLine("TCP client: Sending the number of bytes the client is sending...");

        byteCount = BitConverter::GetBytes(sendBuffer->Length);

        tcpStream->Write(byteCount, 0, byteCount->Length);

        // Send the actual data

        Console::WriteLine("TCP client: Sending the actual data...");

        tcpStream->Write(sendBuffer, 0, sendBuffer->Length);

        tcpStream->Read(byteCount, 0, byteCount->Length);

        // Read how many bytes the server is responding with

        Console::WriteLine("TCP client: Reading how many bytes the server is responding with...");

        bytesToRead = BitConverter::ToInt32(byteCount, 0);

        // Receive the data

        Console::WriteLine("TCP client: Receiving, reading & displaying the data...");

        while (bytesToRead > 0)

        {

            // Make sure we don't read beyond what the first message indicates

            //    This is important if the client is sending multiple "messages" --

            //    but in this sample it sends only one

            if (bytesToRead < receiveBuffer->Length)

                nextReadCount = bytesToRead;

            else

                nextReadCount = receiveBuffer->Length;

            // Read the data

            rc = tcpStream->Read(receiveBuffer, 0, nextReadCount);

            // Display what was read

            String^ readText = Text::Encoding::ASCII->GetString(receiveBuffer, 0, rc);

            Console::WriteLine("TCP client: Received: {0}", readText);

            bytesToRead -= rc;

        }

    }

    catch (SocketException^ err)

    {

        // Exceptions on the TcpListener are caught here

        Console::WriteLine("Socket error\n  - {0}", err->Message);

    }

    catch (IO::IOException^ err)

    {

        // Exceptions on the NetworkStream are caught here

        Console::WriteLine("TCP client: I/O error: {0}", err->Message);

    }

    finally

    {

        // Close any remaining open resources

        Console::WriteLine("TCP client: Closing all the opening resources...");

        if (tcpStream != nullptr)

            tcpStream->Close();

        if (simpleTcp != nullptr)

            simpleTcp->Close();

    }

    return 0;

}