C#的HTTP 客户端和服务

在网络编程中，HTTP（超文本传输协议）是应用最为广泛的协议之一。C#提供了强大的类库来支持HTTP通信，包括HttpClient用于客户端请求，以及HttpListener用于服务端监听。本文将详细介绍如何在C#中使用这些工具进行HTTP通信。

HTTP客户端：HttpClient
HttpClient是.NET中用于发送HTTP请求和接收HTTP响应的类。它支持同步和异步操作，推荐使用其异步方法来避免阻塞主线程。

创建HttpClient实例
using System;
using System.Net.Http;
using System.Threading.Tasks;

class Program
{
static async Task Main(string[] args)
{
using (var client = new HttpClient())
{
client.BaseAddress = new Uri(“https://api.example.com”);
HttpResponseMessage response = await client.GetAsync("/data");
response.EnsureSuccessStatusCode();
string responseBody = await response.Content.ReadAsStringAsync();
Console.WriteLine(responseBody);
}
}
}
发送GET请求
cstring result = await httpClient.GetStringAsync(“https://api.example.com/data”);
发送POST请求
var content = new StringContent(“key=value”, Encoding.UTF8, “application/x-www-form-urlencoded”);
HttpResponseMessage response = await httpClient.PostAsync(“https://api.example.com/data”, content);
错误处理
try
{
HttpResponseMessage response = await httpClient.GetAsync(“https://api.example.com/data”);
response.EnsureSuccessStatusCode();
string responseBody = await response.Content.ReadAsStringAsync();
}
catch (HttpRequestException e)
{
Console.WriteLine("\nException Caught!");
Console.WriteLine("Message :{0} ", e.Message);
}
HTTP服务端：HttpListener
HttpListener是.NET中用于创建HTTP服务端的类。它提供了一个简单的方式来监听和响应HTTP请求。

创建和启动服务端
using System;
using System.IO;
using System.Net;
using System.Threading.Tasks;

class Program
{
static async Task Main(string[] args)
{
HttpListener listener = new HttpListener();
listener.Prefixes.Add(“http://localhost:8080/”);
listener.Start();
Console.WriteLine(“Listening…”);

    while (true)
    {
        HttpListenerContext context = await listener.GetContextAsync();
        HttpListenerRequest request = context.Request;
        HttpListenerResponse response = context.Response;

        string responseString = "Hello, world!";
        byte[] buffer = System.Text.Encoding.UTF8.GetBytes(responseString);

        response.ContentLength64 = buffer.Length;
        Stream output = response.OutputStream;
        output.Write(buffer, 0, buffer.Length);
        // You must close the output stream.
        output.Close();
    }
}

}
处理请求
while (listener.IsListening)
{
HttpListenerContext context = await listener.GetContextAsync();
if (context.Request.Url.AbsolutePath == “/data”)
{
// Handle request for /data
}
}
安全性
在服务端，安全性是一个重要的考虑因素。你应该确保：

验证所有输入数据。
使用HTTPS来加密传输的数据。
设置适当的HTTP响应头，如X-Content-Type-Options，X-Frame-Options等。