How to C# Socket programming

C# simplifies the network programming through its namespaces like System.Net and System.Net.Sockets . A Socket is an End-Point of To and From (Bidirectional) communication link between two programs (Server Program and Client Program ) running on the same network . We need two programs for communicating a socket application in C#. A Server Socket Program ( Server ) and a Client Socket Program ( Client ) . C# Server Socket Program: A C# Server Socket Program running on a computer has a socket that bound to a Port Number on the same computer and listening to the client's incoming requests.

C# Client Socket Program: A C# Client Socket Program have to know the IP Address ( Hostname ) of the computer that the C# Server Socket Program resides and the Port Number assign for listening for client's request .

Once the connection is established between Server and Client , they can communicate (read or write ) through their own sockets.

There are two types of communication protocol uses for Socket Programming in C# , they are TCP/IP ( Transmission Control Protocol/Internet protocol ) Communication and UDP/IP ( User Datagram Protocol/Internet protocol ) Communication .

In the following section we are going to communicate a C# Server Socket Program and C# Client Socket Program using TCP/IP Communication Protocol.

Code for Client Program

using System;

using System.Windows.Forms;

using System.Net.Sockets;

using System.Text; 

namespace WindowsApplication1

{

    public partial class Form1 : Form

    {

        System.Net.Sockets.TcpClient clientSocket = new System.Net.Sockets.TcpClient();

        public Form1()

        {

           InitializeComponent();

        }

        private void Form1_Load(object sender, EventArgs e)

        {

            msg("Client Started");

            clientSocket.Connect("127.0.0.1", 8888);

            label1.Text = "Client Socket Program - Server Connected ...";

        }

        private void button1_Click(object sender, EventArgs e)

        {

            NetworkStream serverStream = clientSocket.GetStream();

            byte[] outStream = System.Text.Encoding.ASCII.GetBytes("Message from Client$");

            serverStream.Write(outStream, 0, outStream.Length);

            serverStream.Flush();

            byte[] inStream = new byte[10025];

            serverStream.Read(inStream, 0, (int)clientSocket.ReceiveBufferSize);

            string returndata = System.Text.Encoding.ASCII.GetString(inStream);

            msg("Data from Server : " + returndata);

        }

        public void msg(string mesg)

        {

            textBox1.Text = textBox1.Text + Environment.NewLine + " >> " + mesg;

        } 

    }

}

Code for Server Program

using System;

using System.Net.Sockets;

using System.Text;

namespace ConsoleApplication1

{

    class Program

    {

        static void Main(string[] args)

        {

            TcpListener serverSocket = new TcpListener(8888);

            int requestCount = 0;

            TcpClient clientSocket = default(TcpClient);

            serverSocket.Start();

            Console.WriteLine(" >> Server Started");

            clientSocket = serverSocket.AcceptTcpClient();

            Console.WriteLine(" >> Accept connection from client");

            requestCount = 0;

            while ((true))

            {

                try

                {

                    requestCount = requestCount + 1;

                    NetworkStream networkStream = clientSocket.GetStream();

                    byte[] bytesFrom = new byte[10025];

                    networkStream.Read(bytesFrom, 0, (int)clientSocket.ReceiveBufferSize);

                    string dataFromClient = System.Text.Encoding.ASCII.GetString(bytesFrom);

                    dataFromClient = dataFromClient.Substring(0, dataFromClient.IndexOf("$"));

                    Console.WriteLine(" >> Data from client - " + dataFromClient);

                    string serverResponse = "Server response " + Convert.ToString(requestCount);

                    Byte[] sendBytes = Encoding.ASCII.GetBytes(serverResponse);

                    networkStream.Write(sendBytes, 0, sendBytes.Length);

                    networkStream.Flush();

                    Console.WriteLine(" >> " + serverResponse);

                }

                catch (Exception ex)

                {

                    Console.WriteLine(ex.ToString());

                }

            }

            clientSocket.Close();

            serverSocket.Stop();

            Console.WriteLine(" >> exit");

            Console.ReadLine();

        }

    }

}

The above picture shows a Server and Client communication interfaces in C#.

C# Server Socket Program:

The Server Socket Program is done through a C# Console based application . Here the Server is listening for the Client's request , and when the C# Server gets a request from Client socket , the Server sends a response to the Client . Click the following link to see in detail of a C# Server Socket Program.

C# Client Socket Program:

The C# Client Socket Program is a windows based application . When the C# Client program execute , it will establish a connection to the C# Server program and send request to the Server , at the same time it also receive the response from C# Server . Click the following link to see in detail of C# Client Socket Program.

How to run this program ?

The C# Socket Program has two sections.

1. C# Server Socket Program

2. C# Client Socket Program

When you finish coding and build the Server and Client program , First you have to start C# Server Socket Program from DOS prompt , then you will get a message "Server Started" in your DOS screen, where the server program is running .

Next step is to start C# Client Socket Program in the same computer or other computers on the same network . When you start the client program , it will establish a connection to the Server and get a message in client screen " Client Started " , at the same time you can see a message in the Server screen "Accept connection from client" .

Now your C# Server Socket Program and C# Client Socket Program is get connected and communicated . If you want to communicate the Server and Client again , click the button in the client program , then you can see new messages in the Server and Client programs displayed.