C# TCP Client Program Example

Create a new console application project and you might want to use TcpClientSampleCS as the name.

using System;

using System.Net;

using System.Net.Sockets;

/// <summary>

/// Displays simple usage information.

/// </summary>

static public 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();

}

static void Main(string[ ] args)

        {

            // Initial/default values

            string serverAddress = "localhost";

            ushort serverPort = 5150;

            int bufferSize = 1024;

            usage();

            // Parse the command line

            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 = System.Convert.ToUInt16(args[++i]);

                                break;

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

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

                                break;

                            default:

                                usage();

                                return;

                        }

                    }

                }

                catch

                {

                    usage();

                    return;

                }

            }

            TcpClient simpleTcp = null;

            NetworkStream tcpStream = null;

            byte[] sendBuffer = new byte[bufferSize], receiveBuffer = new byte[bufferSize], 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 = new 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 = System.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("TCP client: Socket error occurred: {0}", err.Message);

            }

            catch (System.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 != null)

                    tcpStream.Close();

                if (simpleTcp != null)

                    simpleTcp.Close();

            }

        }

Imports System

Imports System.Net

Imports System.Net.Sockets

' Displays simple usage information.       

    Shared Sub usage()

        Console.WriteLine("Usage: TcpClientSampleVB [-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()

    End Sub

Shared Sub Main()

        Dim serverAddress As String = "localhost"

        Dim serverPort As Short = 5150

        Dim bufferSize As Integer = 1024

        ' Parse the command line

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

        Dim i As Integer

        usage()

        For i = 1 To args.GetUpperBound(0)

            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 "n" ' String name or address of server to connect to

                            i = i + 1

                            serverAddress = args(i)

                        Case "p" ' Port number for the destination

                            i = i + 1

                            serverPort = 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 simpleTcp 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.GetUpperBound(0) - 1

            sendBuffer(i) = CByte(65)

        Next

        Try

            ' Create the client and indicate the server to connect to

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

            simpleTcp = New TcpClient(serverAddress, serverPort)

            ' Retrieve the NetworkStream so we can do Read and Write

            Console.WriteLine("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("Sending the number of bytes...")

            byteCount = BitConverter.GetBytes(sendBuffer.GetUpperBound(0))

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

            ' Send the actual data

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

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

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

            ' Read how many bytes the server is responding with

            Console.WriteLine("Reading how many bytes the server is responding with...")

            bytesToRead = BitConverter.ToInt32(byteCount, 0)

            ' Receive the data

            Console.WriteLine("Receive, read & display 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.GetUpperBound(0)) Then

                    nextReadCount = bytesToRead

                Else

                    nextReadCount = receiveBuffer.GetUpperBound(0)

                End If

                ' Read the data

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

                ' Display what was read

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

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

                bytesToRead -= rc

            End While

        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(tcpStream)) Then

                tcpStream.Close()

            End If

            If (Not IsNothing(simpleTcp)) Then

                simpleTcp.Close()

            End If

        End Try

    End Sub