Receive HTTP Post via ASP.Net Generic Handler(服務端與用戶端定時通訊機制)

假設我們要提供一個小小的服務，採用HTTP協議進行通訊，用戶端 POST 一些資料到伺服器上。用戶端不一定是PC，更不一定會按照一個Web Form的格式來提交資料，它可能是一個運行在PC上的Desktop Application，也可能是一個行動裝置。

伺服器端接收這樣的請求極其簡單，下面寥寥數行代碼即可實現：

在Web網站中建立一個Generic Handler（*.ashx），代碼如下：

[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; }    }}

然後我們寫一個簡單的用戶端來測試它。在這個用戶端裡我們實現了一個類HttpClient來進行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;        }    }}

然後我們這樣就能得到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! 測試 @");
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! 測試 @");Console.OutputEncoding = System.Text.Encoding.UTF8;Console.WriteLine(response);

假設Client與Server兩端都約定好採取某個格式對資料進行序列化與還原序列化，例如都採用Json，用戶端把對象通過Json封裝後Post給Server，Server再採用Json將對象從Json字串中解析出來，這樣進行資料傳遞是便利的。再假設我們要壓縮傳送出的資料量，那麼可以進行gzip壓縮與解壓。又假設我們要考慮安全性，那麼我們可以在對象的結構中添加security token進行認證，以及採用某種密碼編譯演算法對字串進行加密與解密。怎麼發揮就看您具體的應用了，構建一個屬於您自己的輕量的service易如反掌。