Socket Programming Overview

General Overview of Socket Programming Example

This example demonstrates a basic implementation of a TCP server and client using C# and the System.Net.Sockets namespace. Socket programming enables communication between two nodes on a network, and this example showcases how to create a server that listens for incoming connections and a client that connects to the server, exchanges messages, and then closes the connection.

Server Code Explanation

The server code initializes a socket to listen for incoming TCP connections. It binds the socket to an endpoint (defined by an IP address and port), starts listening for connections, and handles client requests in a loop. The server receives a message from the client, sends a response, and th n closes the connection.

1. Namespace and Class Setup: namespace Servercore and class Program define the scope and main class.
2. DNS and IP Resolution:
   • string host = Dns.GetHostName(): Gets the local machine’s hostname.
   • IPHostEntry ipHost = Dns.GetHostEntry(host): Resolves the hostname to an IPHostEntry instance containing IP addresses.
   • IPAddress ipAddr = ipHost.AddressList[0]: Selects the first IP address.
   • IPEndPoint endPoint = new IPEndPoint(ipAddr, 7777): Creates an endpoint with the IP address and port 7777.
3. Socket Creation:
   • Socket listenSocket = new Socket(endPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp): Creates a TCP socket.
4. Binding and Listening:
   • listenSocket.Bind(endPoint): Binds the socket to the endpoint.
   • listenSocket.Listen(10): Starts listening for incoming connections, with a backlog of 10.
5. Handling Client Connections:
   • In a while (true) loop:
     • Socket clientSocket = listenSocket.Accept(): Accepts an incoming connection.
     • byte[] recvBuff = new byte[1024]: Buffer for receiving data.
     • int recvBytes = clientSocket.Receive(recvBuff): Receives data from the client.
     • string recvData = Encoding.UTF8.GetString(recvBuff, 0, recvBytes): Decodes the received data.
     • Console.WriteLine($"[From Client]: {recvData}"): Prints the received data.
     • byte[] sendBuff = Encoding.UTF8.GetBytes("Welcome to Mati's Server!"): Prepares a response.
     • clientSocket.Send(sendBuff): Sends the response to the client.
     • clientSocket.Shutdown(SocketShutdown.Both): Shuts down the connection.
     • clientSocket.Close(): Closes the connection.
6. Exception Handling:
   • catch (Exception e): Catches and prints any exceptions that occur.

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

   namespace Servercore
   {
    class Program
    {
        static void Main(string[] args)
        {
            // get the hostname of the local machine
            string host = Dns.GetHostName();
               
            // get the IP address associated with the hostname
            IPHostEntry ipHost = Dns.GetHostEntry(host);
            IPAddress ipAddr = ipHost.AddressList[0];
               
            // define the endpoint with IP address and port
            IPEndPoint endPoint = new IPEndPoint(ipAddr, 7777);
   
            // create a socket to listen for incoming connections
            Socket listenSocket = new Socket(endPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
   
            try
            {
                // bind the socket to the endpoint
                listenSocket.Bind(endPoint);
   
                // start listening for incoming connections
                listenSocket.Listen(10);
   
                while (true)
                {
                    Console.WriteLine("Listening...");
   
                    // accept an incoming connection
                    Socket clientSocket = listenSocket.Accept();
   
                    // receive data from the client
                    byte[] recvBuff = new byte[1024];
                    int recvBytes = clientSocket.Receive(recvBuff);
                    string recvData = Encoding.UTF8.GetString(recvBuff, 0, recvBytes);
                    Console.WriteLine($"[From Client]: {recvData}");
   
                    // send a response to the client
                    byte[] sendBuff = Encoding.UTF8.GetBytes("Welcome to Mati's Server!");
                    clientSocket.Send(sendBuff);
   
                    // close the connection
                    clientSocket.Shutdown(SocketShutdown.Both);
                    clientSocket.Close();
                }
            }
            catch (Exception e)
            {
                Console.WriteLine(e.ToString());
            }
        }
    }
   }
   

   Client Code Explanation

The client code initializes a socket, connects to the server, sends a message, receives a response, and then closes the connection.

1. Namespace and Class Setup: namespace DummyClient and class Program define the scope and main class.
2. DNS and IP Resolution:
   • string host = Dns.GetHostName(): Gets the local machine’s hostname.
   • IPHostEntry ipHost = Dns.GetHostEntry(host): Resolves the hostname to an IPHostEntry instance containing IP addresses.
   • IPAddress ipAddr = ipHost.AddressList[0]: Selects the first IP address.
   • IPEndPoint endPoint = new IPEndPoint(ipAddr, 7777): Creates an endpoint with the IP address and port 7777.
3. Socket Creation:
   • Socket socket = new Socket(endPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp): Creates a TCP socket.
4. Connecting to Server:
   • socket.Connect(endPoint): Connects to the server.
   • Console.WriteLine($"Connected to {socket.RemoteEndPoint.ToString()}"): Prints the connection status.
5. Sending and Receiving Data:
   • byte[] sendBuff = Encoding.UTF8.GetBytes("Hello Mati!"): Prepares a message to send.
   • int sendBytes = socket.Send(sendBuff): Sends the message to the server.
   • byte[] recvBuff = new byte[1024]: Buffer for receiving data.
   • int recvBytes = socket.Receive(recvBuff): Receives data from the server.
   • string recvData = Encoding.UTF8.GetString(recvBuff, 0, recvBytes): Decodes the received data.
   • Console.WriteLine($"[From Server]: {recvData}"): Prints the received data.
6. Closing the Connection:
   • socket.Shutdown(SocketShutdown.Both): Shuts down the connection.
   • socket.Close(): Closes the connection.
7. Exception Handling:
   • catch (Exception ex): Catches and prints any exceptions that occur.

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

namespace DummyClient
{
    class Program
    {
        static void Main(string[] args)
        {
            string host = Dns.GetHostName();
            IPHostEntry ipHost = Dns.GetHostEntry(host);
            IPAddress ipAddr = ipHost.AddressList[0];
            IPEndPoint endPoint = new IPEndPoint(ipAddr, 7777);

            // create a socket to connect to the server
            Socket socket = new Socket(endPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp);

            try
            {
                // connect to the server
                socket.Connect(endPoint);
                Console.WriteLine($"Connected to {socket.RemoteEndPoint.ToString()}");

                // send a message to the server
                byte[] sendBuff = Encoding.UTF8.GetBytes("Hello Mati!");
                int sendBytes = socket.Send(sendBuff);

                // receive a message from the server
                byte[] recvBuff = new byte[1024];
                int recvBytes = socket.Receive(recvBuff);
                string recvData = Encoding.UTF8.GetString(recvBuff, 0, recvBytes);
                Console.WriteLine($"[From Server]: {recvData}");

                // close the connection
                socket.Shutdown(SocketShutdown.Both);
                socket.Close();
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
        }
    }
}