.NET Networking

This section provides comprehensive documentation on how to perform network operations using the .NET Framework and .NET Core.

Overview of .NET Networking

The .NET platform offers a rich set of classes for network programming, abstracting away much of the complexity of underlying network protocols. These classes are primarily found in the System.Net namespace and its sub-namespaces.

Key Features:

Support for various network protocols like HTTP, FTP, SMTP, POP3, and TCP.
Classes for creating network clients and servers.
Asynchronous operations for efficient network communication.
Tools for working with IP addresses, host names, and DNS resolution.
Security features for network communications, including SSL/TLS.

Common Networking Tasks

Making HTTP Requests

The HttpClient class is the modern, recommended way to send HTTP requests. It supports asynchronous operations and offers flexibility in configuring requests.

using System.Net.Http;
using System.Threading.Tasks;

public class HttpExample
{
    public static async Task GetRequestAsync()
    {
        using (HttpClient client = new HttpClient())
        {
            try
            {
                HttpResponseMessage response = await client.GetAsync("https://example.com/api/data");
                response.EnsureSuccessStatusCode(); // Throws if HTTP status code is not 2xx
                string responseBody = await response.Content.ReadAsStringAsync();
                Console.WriteLine(responseBody);
            }
            catch (HttpRequestException e)
            {
                Console.WriteLine($"Request error: {e.Message}");
            }
        }
    }
}

Working with TCP Sockets

For lower-level network communication, System.Net.Sockets provides classes like Socket, TcpClient, and TcpListener.

`System.Net.Sockets.TcpClient`

Represents a Transmission Control Protocol (TCP) client, which provides a stream for sending and receiving data over a network.

`System.Net.Sockets.TcpListener`

Listens for incoming connection requests.

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

public class TcpServerExample
{
    public static void StartServer(int port)
    {
        TcpListener server = null;
        try
        {
            server = new TcpListener(IPAddress.Any, port);
            server.Start();

            Console.WriteLine("Server started. Waiting for connections...");

            while (true)
            {
                TcpClient client = server.AcceptTcpClient();
                Console.WriteLine("Client connected!");

                // Handle client connection in a separate thread or task
                // For simplicity, we'll just handle one here
                NetworkStream stream = client.GetStream();
                byte[] buffer = new byte[1024];
                int bytesRead = stream.Read(buffer, 0, buffer.Length);
                string data = Encoding.ASCII.GetString(buffer, 0, bytesRead);
                Console.WriteLine($"Received: {data}");

                byte[] msg = Encoding.ASCII.GetBytes("Hello from server!");
                stream.Write(msg, 0, msg.Length);
                Console.WriteLine("Sent: Hello from server!");

                client.Close();
            }
        }
        catch (SocketException e)
        {
            Console.WriteLine($"SocketException: {e}");
        }
        finally
        {
            server?.Stop();
        }
    }
}

DNS Resolution

Use the Dns class to resolve host names to IP addresses and vice versa.

using System.Net;

public class DnsExample
{
    public static void ResolveHostname(string hostname)
    {
        try
        {
            IPAddress[] addresses = Dns.GetHostAddresses(hostname);
            Console.WriteLine($"IP addresses for {hostname}:");
            foreach (var address in addresses)
            {
                Console.WriteLine($"- {address}");
            }
        }
        catch (SocketException e)
        {
            Console.WriteLine($"Error resolving {hostname}: {e.Message}");
        }
    }
}

.NET Documentation