在現(xiàn)今軟件開發(fā)中，網(wǎng)絡(luò)編程是非常重要的一部分，本文簡要介紹下網(wǎng)絡(luò)編程的概念和實踐。
C#網(wǎng)絡(luò)編程的主要內(nèi)容包括以下幾個方面?：
:
上圖引用大佬的圖，大家也關(guān)注一下，有技術(shù)有品質(zhì)，有國有家，情懷滿滿的楊老師（不得不去仰慕一番哈哈）
https://blog.csdn.net/Eastmount/article/details/9321153

1. 底層網(wǎng)絡(luò)協(xié)議類?

如NetworkStream、TcpClient與TcpListener、UdpClient等，這些類提供了更底層的網(wǎng)絡(luò)操作接口，適用于需要直接控制網(wǎng)絡(luò)連接和數(shù)據(jù)處理的情況?

1. TCP 通信

使用 TcpListener 和 TcpClient 進行 通訊

• TCP 服務(wù)器端示例

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;class TcpServerExample
{static async Task Main(string[] args){// 創(chuàng)建一個 TCP/IP 套接字TcpListener listener = new TcpListener(IPAddress.Any, 13000);listener.Start();Console.WriteLine("Server started. Waiting for connections...");while (true){// 接受傳入連接TcpClient client = await listener.AcceptTcpClientAsync();Console.WriteLine("Client connected.");// 處理客戶端請求_ = HandleClient(client);}}static async Task HandleClient(TcpClient client){try{NetworkStream stream = client.GetStream();// 接收數(shù)據(jù)byte[] buffer = new byte[256];int bytesRead = await stream.ReadAsync(buffer, 0, buffer.Length);string request = Encoding.ASCII.GetString(buffer, 0, bytesRead);Console.WriteLine("Received: " + request);// 發(fā)送響應(yīng)string response = "Hello, Client!";byte[] responseData = Encoding.ASCII.GetBytes(response);await stream.WriteAsync(responseData, 0, responseData.Length);Console.WriteLine("Sent: " + response);// 關(guān)閉連接client.Close();}catch (Exception ex){Console.WriteLine("Error: " + ex.Message);}}
}

• TCP 客戶端示例

using System;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;class TcpClientExample
{static async Task Main(string[] args){try{// 創(chuàng)建一個 TCP/IP 套接字TcpClient client = new TcpClient();await client.ConnectAsync("127.0.0.1", 13000);Console.WriteLine("Connected to server.");NetworkStream stream = client.GetStream();// 發(fā)送數(shù)據(jù)string message = "Hello, Server!";byte[] data = Encoding.ASCII.GetBytes(message);await stream.WriteAsync(data, 0, data.Length);Console.WriteLine("Sent: " + message);// 接收響應(yīng)byte[] buffer = new byte[256];int bytesRead = await stream.ReadAsync(buffer, 0, buffer.Length);string response = Encoding.ASCII.GetString(buffer, 0, bytesRead);Console.WriteLine("Received: " + response);// 關(guān)閉連接client.Close();}catch (Exception e){Console.WriteLine("Error: " + e.Message);}}
}

2. UDP 通信

使用 UdpClient 進行通訊

• UDP 服務(wù)器端示例

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;class UdpServerExample
{static async Task Main(string[] args){// 創(chuàng)建一個 UDP/IP 套接字UdpClient listener = new UdpClient(11000);IPEndPoint remoteEndPoint = new IPEndPoint(IPAddress.Any, 0);Console.WriteLine("UDP Server started. Listening on port 11000...");while (true){// 接收數(shù)據(jù)byte[] buffer = await listener.ReceiveAsync();string request = Encoding.ASCII.GetString(buffer);Console.WriteLine("Received: " + request + " from " + remoteEndPoint.ToString());// 發(fā)送響應(yīng)string response = "Hello, Client!";byte[] responseData = Encoding.ASCII.GetBytes(response);await listener.SendAsync(responseData, responseData.Length, remoteEndPoint);Console.WriteLine("Sent: " + response);}}
}

• UDP 客戶端示例

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;class UdpClientExample
{static async Task Main(string[] args){try{// 創(chuàng)建一個 UDP/IP 套接字UdpClient client = new UdpClient();IPEndPoint remoteEP = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 11000);// 發(fā)送數(shù)據(jù)string message = "Hello, Server!";byte[] data = Encoding.ASCII.GetBytes(message);await client.SendAsync(data, data.Length, remoteEP);Console.WriteLine("Sent: " + message);// 接收響應(yīng)UdpReceiveResult result = await client.ReceiveAsync();string response = Encoding.ASCII.GetString(result.Buffer);Console.WriteLine("Received: " + response + " from " + result.RemoteEndPoint.ToString());// 關(guān)閉連接client.Close();}catch (Exception e){Console.WriteLine("Error: " + e.Message);}}
}

3. 使用 NetworkStream 進行自定義協(xié)議通信

NetworkStream 提供了一個流式接口，可以用于讀取和寫入網(wǎng)絡(luò)數(shù)據(jù)。以下是一個使用 NetworkStream 的示例，展示如何實現(xiàn)一個簡單的自定義協(xié)議。

• 自定義協(xié)議服務(wù)器端示例

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;class CustomProtocolServerExample
{static async Task Main(string[] args){// 創(chuàng)建一個 TCP/IP 套接字TcpListener listener = new TcpListener(IPAddress.Any, 13000);listener.Start();Console.WriteLine("Server started. Waiting for connections...");while (true){// 接受傳入連接TcpClient client = await listener.AcceptTcpClientAsync();Console.WriteLine("Client connected.");// 處理客戶端請求_ = HandleClient(client);}}static async Task HandleClient(TcpClient client){try{NetworkStream stream = client.GetStream();// 接收數(shù)據(jù)byte[] buffer = new byte[256];int bytesRead = await stream.ReadAsync(buffer, 0, buffer.Length);string request = Encoding.ASCII.GetString(buffer, 0, bytesRead);Console.WriteLine("Received: " + request);// 解析自定義協(xié)議string[] parts = request.Split(':');if (parts.Length == 2 && parts[0] == "COMMAND"){string command = parts[1];Console.WriteLine("Command: " + command);// 處理命令并生成響應(yīng)string response = "ACK: Command received";byte[] responseData = Encoding.ASCII.GetBytes(response);await stream.WriteAsync(responseData, 0, responseData.Length);Console.WriteLine("Sent: " + response);}else{string response = "ERROR: Invalid command format";byte[] responseData = Encoding.ASCII.GetBytes(response);await stream.WriteAsync(responseData, 0, responseData.Length);Console.WriteLine("Sent: " + response);}// 關(guān)閉連接client.Close();}catch (Exception ex){Console.WriteLine("Error: " + ex.Message);}}
}

• 自定義協(xié)議客戶端示例

using System;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;class CustomProtocolClientExample
{static async Task Main(string[] args){try{// 創(chuàng)建一個 TCP/IP 套接字TcpClient client = new TcpClient();await client.ConnectAsync("127.0.0.1", 13000);Console.WriteLine("Connected to server.");NetworkStream stream = client.GetStream();// 發(fā)送自定義協(xié)議命令string message = "COMMAND:Hello";byte[] data = Encoding.ASCII.GetBytes(message);await stream.WriteAsync(data, 0, data.Length);Console.WriteLine("Sent: " + message);// 接收響應(yīng)byte[] buffer = new byte[256];int bytesRead = await stream.ReadAsync(buffer, 0, buffer.Length);string response = Encoding.ASCII.GetString(buffer, 0, bytesRead);Console.WriteLine("Received: " + response);// 關(guān)閉連接client.Close();}catch (Exception e){Console.WriteLine("Error: " + e.Message);}}
}

2.Socket編程?

也就是我們常說的“套接字”，Socket類在System.Net.Sockets命名空間下，是最基本的網(wǎng)絡(luò)操作類，封裝了網(wǎng)絡(luò)連接的創(chuàng)建和關(guān)閉、數(shù)據(jù)的收發(fā)以及網(wǎng)絡(luò)狀態(tài)監(jiān)控等功能。通過Socket類，可以實現(xiàn)基于TCP和UDP的網(wǎng)絡(luò)通信?。

1. 使用 Socket 類進行 TCP 通信

TCP 服務(wù)器端示例

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;class TcpServerExample
{static async Task Main(string[] args){// 創(chuàng)建一個 TCP/IP 套接字Socket listener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);// 綁定套接字到本地端口IPEndPoint localEndPoint = new IPEndPoint(IPAddress.Any, 13000);listener.Bind(localEndPoint);// 監(jiān)聽傳入連接listener.Listen(10);Console.WriteLine("Server started. Waiting for connections...");while (true){// 接受傳入連接Socket handler = await listener.AcceptAsync();Console.WriteLine("Client connected.");// 處理客戶端請求_ = HandleClient(handler);}}static async Task HandleClient(Socket handler){try{// 接收數(shù)據(jù)byte[] buffer = new byte[256];int bytesReceived = await handler.ReceiveAsync(new ArraySegment<byte>(buffer), SocketFlags.None);string request = Encoding.ASCII.GetString(buffer, 0, bytesReceived);Console.WriteLine("Received: " + request);// 發(fā)送響應(yīng)string response = "Hello, Client!";byte[] responseData = Encoding.ASCII.GetBytes(response);await handler.SendAsync(new ArraySegment<byte>(responseData), SocketFlags.None);Console.WriteLine("Sent: " + response);// 關(guān)閉連接handler.Shutdown(SocketShutdown.Both);handler.Close();}catch (Exception ex){Console.WriteLine("Error: " + ex.Message);}}
}

TCP 客戶端示例

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;class TcpClientExample
{static async Task Main(string[] args){try{// 創(chuàng)建一個 TCP/IP 套接字Socket client = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);// 連接到服務(wù)器IPEndPoint remoteEP = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 13000);await client.ConnectAsync(remoteEP);Console.WriteLine("Connected to server.");// 發(fā)送數(shù)據(jù)string message = "Hello, Server!";byte[] data = Encoding.ASCII.GetBytes(message);await client.SendAsync(new ArraySegment<byte>(data), SocketFlags.None);Console.WriteLine("Sent: " + message);// 接收響應(yīng)byte[] buffer = new byte[256];int bytesReceived = await client.ReceiveAsync(new ArraySegment<byte>(buffer), SocketFlags.None);string response = Encoding.ASCII.GetString(buffer, 0, bytesReceived);Console.WriteLine("Received: " + response);// 關(guān)閉連接client.Shutdown(SocketShutdown.Both);client.Close();}catch (Exception e){Console.WriteLine("Error: " + e.Message);}}
}

2. 使用 Socket 類進行 UDP 通信

UDP 服務(wù)器端示例

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;class UdpServerExample
{static async Task Main(string[] args){// 創(chuàng)建一個 UDP/IP 套接字Socket listener = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);// 綁定套接字到本地端口IPEndPoint localEndPoint = new IPEndPoint(IPAddress.Any, 11000);listener.Bind(localEndPoint);Console.WriteLine("UDP Server started. Waiting for messages...");while (true){// 接收數(shù)據(jù)EndPoint remoteEndPoint = new IPEndPoint(IPAddress.Any, 0);byte[] buffer = new byte[256];int bytesReceived = await listener.ReceiveFromAsync(new ArraySegment<byte>(buffer), SocketFlags.None, remoteEndPoint);string request = Encoding.ASCII.GetString(buffer, 0, bytesReceived);Console.WriteLine("Received: " + request + " from " + remoteEndPoint.ToString());// 發(fā)送響應(yīng)string response = "Hello, Client!";byte[] responseData = Encoding.ASCII.GetBytes(response);await listener.SendToAsync(new ArraySegment<byte>(responseData), SocketFlags.None, remoteEndPoint);Console.WriteLine("Sent: " + response);}}
}

UDP 客戶端示例

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;class UdpClientExample
{static async Task Main(string[] args){try{// 創(chuàng)建一個 UDP/IP 套接字Socket client = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);// 連接到服務(wù)器IPEndPoint remoteEP = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 11000);// 發(fā)送數(shù)據(jù)string message = "Hello, Server!";byte[] data = Encoding.ASCII.GetBytes(message);await client.SendToAsync(new ArraySegment<byte>(data), SocketFlags.None, remoteEP);Console.WriteLine("Sent: " + message);// 接收響應(yīng)EndPoint remoteEndPoint = new IPEndPoint(IPAddress.Any, 0);byte[] buffer = new byte[256];int bytesReceived = await client.ReceiveFromAsync(new ArraySegment<byte>(buffer), SocketFlags.None, remoteEndPoint);string response = Encoding.ASCII.GetString(buffer, 0, bytesReceived);Console.WriteLine("Received: " + response + " from " + remoteEndPoint.ToString());// 關(guān)閉連接client.Close();}catch (Exception e){Console.WriteLine("Error: " + e.Message);}}
}

注意事項

1. 異常處理：使用 try-catch 塊來捕獲和處理異常。
2. 資源管理：確保在使用完 Socket 后調(diào)用 Close 方法來釋放資源。
3. 并發(fā)處理：對于服務(wù)器端，通常需要處理多個客戶端連接，可以使用多線程或異步編程來提高并發(fā)性能。
4. 超時設(shè)置：對于 TCP 連接，可以設(shè)置超時時間來避免長時間等待。

3.WebSocket通信?

WebSocket是一種在單個TCP連接上進行全雙工通訊的協(xié)議?？梢允褂?System.Net.WebSockets 命名空間中的類來創(chuàng)建 WebSocket 服務(wù)器和客戶端。WebSocket通信常用于需要實時數(shù)據(jù)交換的應(yīng)用場景?，適用于需要實時數(shù)據(jù)交換的應(yīng)用場景，如實時聊天、在線游戲、股票行情等。

1.WebSocket 服務(wù)器端示例

以下是一個簡單的 WebSocket 服務(wù)器端示例，使用 HttpListener 來處理 HTTP 請求并升級為 WebSocket 連接。

using System;
using System.IO;
using System.Net;
using System.Net.WebSockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;class WebSocketServerExample
{static async Task Main(string[] args){HttpListener listener = new HttpListener();listener.Prefixes.Add("http://localhost:8080/");listener.Start();Console.WriteLine("WebSocket Server started. Listening on ws://localhost:8080/");while (true){HttpListenerContext context = await listener.GetContextAsync();if (context.Request.IsWebSocketRequest){HttpListenerWebSocketContext webSocketContext = await context.AcceptWebSocketAsync(null);_ = HandleWebSocketConnection(webSocketContext.WebSocket);}else{context.Response.StatusCode = (int)HttpStatusCode.BadRequest;context.Response.Close();}}}static async Task HandleWebSocketConnection(WebSocket webSocket){byte[] buffer = new byte[1024 * 4];WebSocketReceiveResult result = await webSocket.ReceiveAsync(new ArraySegment<byte>(buffer), CancellationToken.None);while (!result.CloseStatus.HasValue){string userMessage = Encoding.UTF8.GetString(new ArraySegment<byte>(buffer, 0, result.Count));Console.WriteLine("Received: " + userMessage);//來自客戶端：將消息回傳給客戶端byte[] responseBuffer = Encoding.UTF8.GetBytes("Echo: " + userMessage);await webSocket.SendAsync(new ArraySegment<byte>(responseBuffer), result.MessageType, result.EndOfMessage, CancellationToken.None);result = await webSocket.ReceiveAsync(new ArraySegment<byte>(buffer), CancellationToken.None);}await webSocket.CloseAsync(result.CloseStatus.Value, result.CloseStatusDescription, CancellationToken.None);webSocket.Dispose();}
}

2.WebSocket 客戶端示例

以下是一個簡單的 WebSocket 客戶端示例，使用 ClientWebSocket 類來連接 WebSocket 服務(wù)器并進行通信。

using System;
using System.Net.WebSockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;class WebSocketClientExample
{static async Task Main(string[] args){using (ClientWebSocket webSocket = new ClientWebSocket()){Uri serverUri = new Uri("ws://localhost:8080/");await webSocket.ConnectAsync(serverUri, CancellationToken.None);Console.WriteLine("Connected to server.");byte[] buffer = new byte[1024 * 4];// 在單獨的任務(wù)中開始接收消息_ = ReceiveMessages(webSocket, buffer);// 向服務(wù)器發(fā)送消息while (webSocket.State == WebSocketState.Open){Console.Write("Enter message to send: ");string message = Console.ReadLine();byte[] messageBuffer = Encoding.UTF8.GetBytes(message);await webSocket.SendAsync(new ArraySegment<byte>(messageBuffer), WebSocketMessageType.Text, true, CancellationToken.None);}}}static async Task ReceiveMessages(ClientWebSocket webSocket, byte[] buffer){while (webSocket.State == WebSocketState.Open){WebSocketReceiveResult result = await webSocket.ReceiveAsync(new ArraySegment<byte>(buffer), CancellationToken.None);if (result.MessageType == WebSocketMessageType.Close){await webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, "Closing", CancellationToken.None);break;}string receivedMessage = Encoding.UTF8.GetString(new ArraySegment<byte>(buffer, 0, result.Count));Console.WriteLine("Received: " + receivedMessage);}}
}

注意事項

1. 異常處理：使用 try-catch 塊來捕獲和處理異常，特別是網(wǎng)絡(luò)相關(guān)的異常。
2. 資源管理：確保在使用完 WebSocket 后調(diào)用 CloseAsync 和 Dispose 方法來釋放資源。
3. 并發(fā)處理：對于服務(wù)器端，通常需要處理多個客戶端連接，可以使用多線程或異步編程來提高并發(fā)性能。
4. 安全性：在生產(chǎn)環(huán)境中，建議使用 wss://（WebSocket Secure）來加密通信，防止數(shù)據(jù)泄露。
5. 心跳機制：為了保持連接活躍，可以定期發(fā)送心跳消息，防止中間設(shè)備關(guān)閉空閑連接。

4. HTTP請求?：

可以使用HttpClient、WebClient、HttpRequestMessage和HttpMessageHandler等類來發(fā)送HTTP請求。這些類提供了發(fā)送GET、POST等請求的方法，并支持異步操作和身份驗證等功能?。

1. HttpClient

HttpClient 是一個現(xiàn)代的、高效的 HTTP 客戶端，支持異步操作，適用于 .NET Core 和 .NET Framework。
主要方法
? GetAsync：發(fā)送 GET 請求。
? PostAsync：發(fā)送 POST 請求。
? PutAsync：發(fā)送 PUT 請求。
? DeleteAsync：發(fā)送 DELETE 請求。
? SendAsync：發(fā)送任意類型的 HTTP 請求。
注意
? 單例模式：HttpClient 實例應(yīng)該盡量復(fù)用，而不是每次請求都創(chuàng)建新的實例。頻繁創(chuàng)建 HttpClient 實例會導(dǎo)致資源泄漏和性能問題。
? 異常處理：使用 EnsureSuccessStatusCode 方法來確保請求成功，否則會拋出 HttpRequestException。
? 超時設(shè)置：設(shè)置合理的超時時間，避免長時間等待。
? 取消請求：使用 CancellationToken 來取消長時間運行的請求。
示例代碼

using System;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;class HttpClientExample
{private static readonly HttpClient client = new HttpClient();static async Task Main(string[] args){try{// 設(shè)置超時時間client.Timeout = TimeSpan.FromSeconds(30);// 發(fā)送 GET 請求HttpResponseMessage response = await client.GetAsync("https://api.example.com/data");response.EnsureSuccessStatusCode(); // 確保請求成功string responseBody = await response.Content.ReadAsStringAsync();Console.WriteLine("GET Response: " + responseBody);// 發(fā)送 POST 請求var content = new StringContent("{\"key\":\"value\"}", System.Text.Encoding.UTF8, "application/json");response = await client.PostAsync("https://api.example.com/post", content);response.EnsureSuccessStatusCode();responseBody = await response.Content.ReadAsStringAsync();Console.WriteLine("POST Response: " + responseBody);}catch (HttpRequestException ex){Console.WriteLine("HTTP Error: " + ex.Message);}catch (TaskCanceledException ex){Console.WriteLine("Request canceled: " + ex.Message);}catch (Exception ex){Console.WriteLine("Error: " + ex.Message);}}
}

2. WebClient

WebClient 是一個較老的類，提供了簡單的同步和異步方法來下載和上傳數(shù)據(jù)。雖然它仍然可用，但推薦使用 HttpClient。
主要方法
? DownloadString：下載字符串內(nèi)容。
? UploadString：上傳字符串內(nèi)容。
? DownloadFile：下載文件。
? UploadFile：上傳文件。

注意
? 同步方法：WebClient 的同步方法會阻塞當前線程，建議使用異步方法。
? 異常處理：使用 try-catch 塊來捕獲和處理異常。
? 資源管理：使用 using 語句來確保 WebClient 實例在使用后被正確釋放。
示例代碼

using System;
using System.Net;class WebClientExample
{static void Main(string[] args){try{using (WebClient client = new WebClient()){// 下載字符串內(nèi)容string response = client.DownloadString("https://api.example.com/data");Console.WriteLine("GET Response: " + response);// 上傳字符串內(nèi)容string uploadData = "{\"key\":\"value\"}";response = client.UploadString("https://api.example.com/post", uploadData);Console.WriteLine("POST Response: " + response);}}catch (WebException ex){Console.WriteLine("Web Error: " + ex.Message);}catch (Exception ex){Console.WriteLine("Error: " + ex.Message);}}
}

3. HttpRequestMessage

HttpRequestMessage 用于構(gòu)建 HTTP 請求，通常與 HttpClient 一起使用，提供更細粒度的控制。
注意
? 請求頭設(shè)置：根據(jù)需要設(shè)置請求頭，例如 Content-Type、Authorization 等。
? 請求體設(shè)置：對于 POST、PUT 等請求，需要設(shè)置請求體內(nèi)容。
? 響應(yīng)處理：處理響應(yīng)內(nèi)容時，注意檢查響應(yīng)狀態(tài)碼和內(nèi)容類型。
示例代碼

using System;
using System.Net.Http;
using System.Threading.Tasks;class HttpRequestMessageExample
{static async Task Main(string[] args){using (HttpClient client = new HttpClient()){try{// 構(gòu)建 GET 請求HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Get, "https://api.example.com/data");HttpResponseMessage response = await client.SendAsync(request);response.EnsureSuccessStatusCode();string responseBody = await response.Content.ReadAsStringAsync();Console.WriteLine("GET Response: " + responseBody);// 構(gòu)建 POST 請求request = new HttpRequestMessage(HttpMethod.Post, "https://api.example.com/post"){Content = new StringContent("{\"key\":\"value\"}", System.Text.Encoding.UTF8, "application/json")};response = await client.SendAsync(request);response.EnsureSuccessStatusCode();responseBody = await response.Content.ReadAsStringAsync();Console.WriteLine("POST Response: " + responseBody);}catch (HttpRequestException ex){Console.WriteLine("HTTP Error: " + ex.Message);}catch (Exception ex){Console.WriteLine("Error: " + ex.Message);}}}
}

4. HttpMessageHandler

HttpMessageHandler 是 HttpClient 的基礎(chǔ)組件，用于處理 HTTP 請求和響應(yīng)。通常情況下，開發(fā)者不需要直接使用 HttpMessageHandler，但在某些高級場景中，可以自定義消息處理器來實現(xiàn)特定的功能。

注意
? 自定義處理：在 SendAsync 方法中添加自定義邏輯，例如日志記錄、請求攔截等。
? 資源管理：確保自定義的消息處理器在使用后被正確釋放。
示例代碼

using System;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;class CustomMessageHandler : DelegatingHandler
{protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken){try{// 在發(fā)送請求之前添加自定義邏輯Console.WriteLine("Sending request to: " + request.RequestUri);// 調(diào)用基類的 SendAsync 方法HttpResponseMessage response = await base.SendAsync(request, cancellationToken);// 在接收響應(yīng)之后添加自定義邏輯Console.WriteLine("Received response from: " + request.RequestUri);return response;}catch (Exception ex){Console.WriteLine("Error in message handler: " + ex.Message);throw;}}
}class HttpMessageHandlerExample
{static async Task Main(string[] args){try{// 創(chuàng)建自定義消息處理器CustomMessageHandler handler = new CustomMessageHandler();// 使用自定義消息處理器創(chuàng)建 HttpClientusing (HttpClient client = new HttpClient(handler)){// 發(fā)送 GET 請求HttpResponseMessage response = await client.GetAsync("https://api.example.com/data");response.EnsureSuccessStatusCode();string responseBody = await response.Content.ReadAsStringAsync();Console.WriteLine("GET Response: " + responseBody);}}catch (HttpRequestException ex){Console.WriteLine("HTTP Error: " + ex.Message);}catch (Exception ex){Console.WriteLine("Error: " + ex.Message);}}
}

總結(jié)
? HttpClient：現(xiàn)代、高效的 HTTP 客戶端，支持異步操作，推薦使用；單例模式、異常處理、超時設(shè)置、取消請求。
? WebClient：較老的類，簡單易用，但推薦使用 HttpClient；同步方法、異常處理、資源管理。
? HttpRequestMessage：用于構(gòu)建 HTTP 請求，通常與 HttpClient 一起使用；請求頭設(shè)置、請求體設(shè)置、響應(yīng)處理。
? HttpMessageHandler：用于處理 HTTP 請求和響應(yīng)，通常用于高級場景；：自定義處理、資源管理。

5.網(wǎng)絡(luò)安全?

C# 網(wǎng)絡(luò)編程中有效地保護應(yīng)用程序的安全。確保數(shù)據(jù)傳輸?shù)陌踩?、正確處理用戶輸入、實施適當?shù)纳矸蒡炞C和授權(quán)機制，以及遵循其他最佳實踐，都是構(gòu)建安全網(wǎng)絡(luò)應(yīng)用程序的關(guān)鍵步驟，包括SSL/TLS加密、密碼安全存儲、防止SQL注入、防止跨站腳本攻擊(XSS)、防止跨站請求偽造(CSRF)、身份驗證和授權(quán)等?。

1. SSL/TLS 加密

using System;
using System.Net.Http;
using System.Threading.Tasks;class HttpsExample
{static async Task Main(string[] args){using (HttpClient client = new HttpClient()){try{HttpResponseMessage response = await client.GetAsync("https://api.example.com/data");response.EnsureSuccessStatusCode();string responseBody = await response.Content.ReadAsStringAsync();Console.WriteLine(responseBody);}catch (HttpRequestException e){Console.WriteLine("\nException Caught!");Console.WriteLine("Message :{0} ", e.Message);}}}
}

2. 密碼安全存儲

使用哈希算法和鹽值來安全地存儲密碼。
示例：使用 PasswordHasher 進行密碼哈希

using Microsoft.AspNetCore.Identity;
using System;class PasswordStorageExample
{static void Main(string[] args){var passwordHasher = new PasswordHasher<string>();string password = "securePassword123";string hashedPassword = passwordHasher.HashPassword(null, password);Console.WriteLine("Hashed Password: " + hashedPassword);PasswordVerificationResult result = passwordHasher.VerifyHashedPassword(null, hashedPassword, password);Console.WriteLine("Verification Result: " + result);}
}

3. 防止 SQL 注入

使用參數(shù)化查詢來防止 SQL 注入。
示例：使用 SqlCommand 進行參數(shù)化查詢

using System;
using System.Data.SqlClient;class SqlInjectionExample
{static void Main(string[] args){string connectionString = "your_connection_string_here";string query = "SELECT * FROM Users WHERE Username = @Username AND Password = @Password";using (SqlConnection connection = new SqlConnection(connectionString)){SqlCommand command = new SqlCommand(query, connection);command.Parameters.AddWithValue("@Username", "user1");command.Parameters.AddWithValue("@Password", "pass1");connection.Open();SqlDataReader reader = command.ExecuteReader();while (reader.Read()){Console.WriteLine(reader["Username"]);}}}
}

4. 防止跨站腳本攻擊 (XSS)

對用戶輸入進行適當?shù)霓D(zhuǎn)義和驗證。
示例：使用 HttpUtility.HtmlEncode 轉(zhuǎn)義 HTML 內(nèi)容

using System;
using System.Web;class XssExample
{static void Main(string[] args){string userInput = "<script>alert('XSS')</script>";string safeOutput = HttpUtility.HtmlEncode(userInput);Console.WriteLine("Safe Output: " + safeOutput);}
}

5. 防止跨站請求偽造 (CSRF)

使用 CSRF 令牌來防止跨站請求偽造。
示例：ASP.NET Core 中的 CSRF 保護
在 ASP.NET Core 中，CSRF 保護是默認啟用的。確保在表單中包含 CSRF 令牌。

@model YourModel<form method="post">@Html.AntiForgeryToken()<!-- Form fields here --><button type="submit">Submit</button>
</form>

6. 身份驗證和授權(quán)

使用身份驗證和授權(quán)機制來保護應(yīng)用程序。
示例：ASP.NET Core 中的身份驗證和授權(quán)
在 Startup.cs 中配置身份驗證和授權(quán)。

public class Startup
{public void ConfigureServices(IServiceCollection services){services.AddAuthentication(options =>{options.DefaultAuthenticateScheme = CookieAuthenticationDefaults.AuthenticationScheme;options.DefaultSignInScheme = CookieAuthenticationDefaults.AuthenticationScheme;options.DefaultChallengeScheme = CookieAuthenticationDefaults.AuthenticationScheme;}).AddCookie();services.AddAuthorization();services.AddControllersWithViews();}public void Configure(IApplicationBuilder app, IWebHostEnvironment env){if (env.IsDevelopment()){app.UseDeveloperExceptionPage();}else{app.UseExceptionHandler("/Home/Error");app.UseHsts();}app.UseHttpsRedirection();app.UseStaticFiles();app.UseRouting();app.UseAuthentication();app.UseAuthorization();app.UseEndpoints(endpoints =>{endpoints.MapControllerRoute(name: "default",pattern: "{controller=Home}/{action=Index}/{id?}");});}
}

7. 其他安全措施

? 輸入驗證：對所有用戶輸入進行驗證，確保其符合預(yù)期格式。
? 輸出編碼：對輸出進行適當?shù)木幋a，防止 XSS 攻擊。
? 最小權(quán)限原則：確保應(yīng)用程序以最小權(quán)限運行，限制不必要的權(quán)限。
? 定期更新和補丁：定期更新所有依賴庫和框架，應(yīng)用最新的安全補丁。
? 日志記錄和監(jiān)控：實施詳細的日志記錄和監(jiān)控，以便及時發(fā)現(xiàn)和響應(yīng)安全事件。

6.多線程與并發(fā)(待續(xù))

? Thread 類：System.Threading.Thread 用于創(chuàng)建和管理線程。
? ThreadPool 類：System.Threading.ThreadPool 用于管理線程池。
? Task 并發(fā)：使用 Task.Run 和 Parallel 類進行并行任務(wù)處理。

7.序列化與反序列化(待續(xù))

? JSON 序列化：使用 System.Text.Json.JsonSerializer 進行 JSON 序列化和反序列化。
? XML 序列化：使用 System.Xml.Serialization.XmlSerializer 進行 XML 序列化和反序列化。

8.網(wǎng)絡(luò)配置(待續(xù))

? 配置文件：使用 appsettings.json 或 app.config 配置網(wǎng)絡(luò)參數(shù)。
? 環(huán)境變量：從環(huán)境變量中讀取網(wǎng)絡(luò)配置信息。