Receive HTTP Post via ASP.Net Generic Handler(服务端与客户端定时通讯机制)

假设我们要提供一个小小的服务，采用HTTP协议进行通讯，客户端 POST 一些数据到服务器上。客户端不一定是PC，更不一定会按照一个Web Form的格式来提交数据，它可能是一个运行在PC上的Desktop Application，也可能是一个移动设备。

服务器端接收这样的请求极其简单，下面寥寥数行代码即可实现：

在Web站点中新建一个Generic Handler（*.ashx），代码如下：

[csharp]

1. <%@ WebHandler Language="C#" Class="Echo" %>
3. using System;
4. using System.Web;
5. using System.IO;
7. public class Echo : IHttpHandler
8. {
9. private System.Text.Encoding DefaultEncoding = System.Text.Encoding.UTF8;
11. public void ProcessRequest (HttpContext context)
12. {
13. context.Response.ContentType = "text/plain";
14. context.Response.ContentEncoding = DefaultEncoding;
16. Stream inputStream = context.Request.InputStream;
17. using (StreamReader reader = new StreamReader(inputStream, DefaultEncoding))
18. {
19. string requestContent = reader.ReadToEnd();
20. string responseContent = string.Format("Received: {0} <== END", requestContent);
22. context.Response.Write(responseContent);
23. }
24. }
26. public bool IsReusable
27. {
28. get { return false; }
29. }
30. }

<%@ WebHandler Language="C#" Class="Echo" %>

using System;
using System.Web;
using System.IO;

public class Echo : IHttpHandler
{
    private System.Text.Encoding DefaultEncoding = System.Text.Encoding.UTF8;
    
    public void ProcessRequest (HttpContext context)
    {
        context.Response.ContentType = "text/plain";
        context.Response.ContentEncoding = DefaultEncoding;

        Stream inputStream = context.Request.InputStream;
        using (StreamReader reader = new StreamReader(inputStream, DefaultEncoding))
        {
            string requestContent = reader.ReadToEnd();
            string responseContent = string.Format("Received: {0} <== END", requestContent);
            
            context.Response.Write(responseContent);
        }
    }

    public bool IsReusable
    {
        get { return false; }
    }
}

然后我们写一个简单的客户端来测试它。在这个客户端里我们实现了一个类HttpClient来进行HTTP POST操作：

[csharp]

1. // -----------------------------------------------------------------------
2. // Http protocol client.
3. // -----------------------------------------------------------------------
5. namespace ConsoleClient
6. {
7. using System;
8. using System.IO;
9. using System.Net;
10. using System.Text;
12. /// <summary>
13. /// Http protocol client.
14. /// </summary>
15. public class HttpClient
16. {
17. /// <summary>
18. /// Post data to specific url and get response content.
19. /// </summary>
20. /// <param name="url">the url to post</param>
21. /// <param name="postData">post data</param>
22. /// <returns>response content</returns>
23. public string Post(string url, string postData)
24. {
25. Uri uri = new Uri(url);
26. HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
27. request.Method = "POST";
28. request.ContentType = "application/x-www-form-urlencoded";
30. Encoding encoding = Encoding.UTF8;
31. byte[] bytes = encoding.GetBytes(postData);
33. request.ContentLength = bytes.Length;
35. using (Stream writer = request.GetRequestStream())
36. {
37. writer.Write(bytes, 0, bytes.Length);
38. writer.Close();
39. }
41. return this.ReadResponse(request);;
42. }
44. /// <summary>
45. /// Read response content from http request result.
46. /// </summary>
47. /// <param name="request">http request object</param>
48. /// <returns>response content.</returns>
49. private string ReadResponse(HttpWebRequest request)
50. {
51. string result = string.Empty;
53. using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
54. {
55. using (Stream responseStream = response.GetResponseStream())
56. {
57. using (StreamReader reader = new StreamReader(responseStream, Encoding.UTF8))
58. {
59. result = reader.ReadToEnd();
60. reader.Close();
61. }
62. }
63. }
65. return result;
66. }
67. }
68. }

// -----------------------------------------------------------------------

// Http protocol client.
// -----------------------------------------------------------------------

namespace ConsoleClient
{
    using System;
    using System.IO;
    using System.Net;
    using System.Text;

    /// <summary>
    /// Http protocol client.
    /// </summary>
    public class HttpClient
    {
        /// <summary>
        /// Post data to specific url and get response content.
        /// </summary>
        /// <param name="url">the url to post</param>
        /// <param name="postData">post data</param>
        /// <returns>response content</returns>
        public string Post(string url, string postData)
        {
            Uri uri = new Uri(url);
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
            request.Method = "POST";
            request.ContentType = "application/x-www-form-urlencoded";

            Encoding encoding = Encoding.UTF8;
            byte[] bytes = encoding.GetBytes(postData);

            request.ContentLength = bytes.Length;

            using (Stream writer = request.GetRequestStream())
            {
                writer.Write(bytes, 0, bytes.Length);
                writer.Close();
            }

            return this.ReadResponse(request);;
        }

        /// <summary>
        /// Read response content from http request result.
        /// </summary>
        /// <param name="request">http request object</param>
        /// <returns>response content.</returns>
        private string ReadResponse(HttpWebRequest request)
        {
            string result = string.Empty;

            using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
            {
                using (Stream responseStream = response.GetResponseStream())
                {
                    using (StreamReader reader = new StreamReader(responseStream, Encoding.UTF8))
                    {
                        result = reader.ReadToEnd();
                        reader.Close();
                    }
                }
            }

            return result;
        }
    }
}

然后我们这样就能得到HTTP POST的返回：

[csharp]

1. // Replace the string content with your actual address please.
2. string defaultUrl = "http://ServerName:8081/WebPath/AnyService.ashx";
4. HttpClient client = new HttpClient();
5. string response = client.Post(defaultUrl, @"abc 123! 测试 @");
7. Console.OutputEncoding = System.Text.Encoding.UTF8;
8. Console.WriteLine(response);

// Replace the string content with your actual address please.
string defaultUrl = "http://ServerName:8081/WebPath/AnyService.ashx";

HttpClient client = new HttpClient();
string response = client.Post(defaultUrl, @"abc 123! 测试 @");

Console.OutputEncoding = System.Text.Encoding.UTF8;
Console.WriteLine(response);

假设Client与Server两端都约定好采取某个格式对数据进行序列化与反序列化，例如都采用Json，客户端把对象通过Json封装后Post给Server，Server再采用Json将对象从Json字符串中解析出来，这样进行数据传递是便利的。再假设我们要压缩传送出的数据量，那么可以进行gzip压缩与解压。又假设我们要考虑安全性，那么我们可以在对象的结构中添加security token进行认证，以及采用某种加密算法对字符串进行加密与解密。怎么发挥就看您具体的应用了，构建一个属于您自己的轻量的service易如反掌。