C#学习第22天：网络编程

网络编程的核心概念

1. 套接字（Sockets）

定义：套接字是网络通信的基本单元，提供了在网络中进行数据交换的端点。
用途：用于TCP/UDP网络通信，支持低级别的网络数据传输。

2.协议

TCP（Transmission Control Protocol）

面向连接：在传输数据之前必须建立连接。
可靠性：提供顺序的数据传输，具备错误校验和重传机制，确保数据的完整性。
流控制：提供拥塞控制，防止网络过载。
适用于需要高可靠性和顺序性的数据传输场景。

UDP（User Datagram Protocol）

无连接：不需要建立或关闭连接，数据包独立传输。
不可靠：没有内置的错误校验和重传机制，数据可能会丢失、重复或无序。
低延迟：因为无连接且简单的头部结构，传输速度快。
适用于需要快速传输且对丢包不敏感的场景。

基本使用

使用TCP套接字

TCP服务器：

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;public class TcpServer
{public static void Main(){TcpListener server = null;try{Int32 port = 13000;IPAddress localAddr = IPAddress.Parse("127.0.0.1");server = new TcpListener(localAddr, port);server.Start();Console.WriteLine("Server started...");while (true){Console.WriteLine("Waiting for a connection... ");TcpClient client = server.AcceptTcpClient();Console.WriteLine("Connected!");NetworkStream stream = client.GetStream();int i;byte[] bytes = new byte[256];while ((i = stream.Read(bytes, 0, bytes.Length)) != 0){string data = Encoding.ASCII.GetString(bytes, 0, i);Console.WriteLine($"Received: {data}");byte[] msg = Encoding.ASCII.GetBytes(data.ToUpper());stream.Write(msg, 0, msg.Length);Console.WriteLine("Sent: {0}", data.ToUpper());}client.Close();}}catch (SocketException e){Console.WriteLine("SocketException: {0}", e);}finally{server.Stop();}}
}

TCP客户端：

using System;
using System.Net.Sockets;
using System.Text;public class TcpClientExample
{public static void Main(){try{Int32 port = 13000;TcpClient client = new TcpClient("127.0.0.1", port);NetworkStream stream = client.GetStream();Console.Write("Enter message: ");string message = Console.ReadLine();byte[] data = Encoding.ASCII.GetBytes(message);stream.Write(data, 0, data.Length);Console.WriteLine("Sent: {0}", message);byte[] responseData = new byte[256];int bytes = stream.Read(responseData, 0, responseData.Length);string response = Encoding.ASCII.GetString(responseData, 0, bytes);Console.WriteLine("Received: {0}", response);stream.Close();client.Close();}catch (ArgumentNullException e){Console.WriteLine("ArgumentNullException: {0}", e);}catch (SocketException e){Console.WriteLine("SocketException: {0}", e);}}
}

使用 UDP 套接字

UDP服务器：

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;public class UdpServer
{public static void Main(){UdpClient server = new UdpClient(11000);IPEndPoint remoteEP = new IPEndPoint(IPAddress.Any, 0);Console.WriteLine("UDP Server is up and waiting for packets...");while (true){byte[] data = server.Receive(ref remoteEP);string message = Encoding.ASCII.GetString(data);Console.WriteLine($"Received: {message} from {remoteEP}");byte[] response = Encoding.ASCII.GetBytes("Echo: " + message);server.Send(response, response.Length, remoteEP);}}
}

UDP客户端：

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;public class UdpClientExample
{public static void Main(){UdpClient client = new UdpClient();client.Connect("127.0.0.1", 11000);Console.Write("Enter message: ");string message = Console.ReadLine();byte[] data = Encoding.ASCII.GetBytes(message);client.Send(data, data.Length);IPEndPoint remoteEP = new IPEndPoint(IPAddress.Any, 0);byte[] responseData = client.Receive(ref remoteEP);string response = Encoding.ASCII.GetString(responseData);Console.WriteLine("Received: {0}", response);client.Close();}
}