TCP/IP Networking in .NET

System.Net.Sockets Namespace

This namespace provides low-level access to network services, including the implementation of the Socket class, which is the core abstraction for network communication.

Key Classes and Concepts:

• Socket: Represents a network endpoint and provides methods for sending and receiving data.
• IPAddress: Represents an IP address.
• EndPoint: An abstract base class representing a network endpoint.
• IPEndPoint: Represents an endpoint of an IP address and port number.
• SocketException: Handles errors that occur during socket operations.

Common Operations:

Creating a Socket:

using System.Net.Sockets;

Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            

Connecting to a Server (Client):

IPAddress ipAddress = IPAddress.Parse("192.168.1.100");
int port = 8080;
IPEndPoint remoteEP = new IPEndPoint(ipAddress, port);

socket.Connect(remoteEP);
            

Listening for Connections (Server):

IPAddress ipAddress = IPAddress.Any; // Listen on all network interfaces
int port = 8080;
IPEndPoint localEP = new IPEndPoint(ipAddress, port);

socket.Bind(localEP);
socket.Listen(10); // Maximum number of pending connections

Socket handler = await socket.AcceptAsync(); // Accept incoming connection
            

Sending and Receiving Data:

byte[] bytes = new byte[1024];
string data = null;

int bytesRec = handler.Receive(bytes);
data = System.Text.Encoding.ASCII.GetString(bytes, 0, bytesRec);

// Send data back to client
byte[] msg = System.Text.Encoding.ASCII.GetBytes("Message received");
handler.Send(msg);

handler.Shutdown(SocketShutdown.Both);
handler.Close();
            

System.Net Namespace

While System.Net.Sockets provides the core TCP/IP implementation, the System.Net namespace offers higher-level abstractions and utility classes for network operations.

Key Classes and Concepts:

• IPAddress: As mentioned above, also resides here.
• Dns: Provides DNS resolution capabilities.
• NetworkInformation: Classes for querying network interface information.

Advanced Topics

Beyond basic socket programming, .NET supports:

• Asynchronous Operations: Using Begin/End methods or the Task Parallel Library (TPL) for non-blocking network I/O, crucial for scalable applications.
• Socket Options: Configuring various socket parameters like buffer sizes, keep-alives, and timeouts.
• Protocol Specifics: Understanding TCP's reliability, ordering, and flow control mechanisms.
• IPv6 Support: Utilizing AddressFamily.InterNetworkV6 for IPv6 communication.