[HTML] Multipart Content-Type

一直不喜歡搞網頁的我，但需要寫一些簡單的測試程式，

只好硬著頭皮去研究，果真沒多久就遇到 Multipart Content-Type的問題

所以就去查請教了一下Google 大神，以下就記錄一下遇到的問題。

1. 目的 :　傳送一個表單，裡面包含 text and file 兩個欄位

2. HTML Syntax : Upload file
a. 畫面：

SME-ID
remote path
local path

b. 語法

<form name="uploadfile" enctype="multipart/form-data"
          action="test/upload_file.jsp" method="post">
SME-ID <input type="text" name="smeID"/>
remote path <input type="text" name="remote"/>
local path <input type="file" name="lcoal" size="50" maxlength="20" />
</form>

3. 透過Wireshark 擷取封包發現

問題：在圖片裡的
(1) boundry=---------------------------101321613017111
(2)              -----------------------------101321613017111　   #起頭多了兩個--
(3)              -----------------------------101321613017111--    #起頭結束多了兩個--
當下覺得太奇怪，原先記憶中，這boundry的部分與分割部分還有結束應該都是一樣的。

4. 結果:由http://www.w3.org/Protocols/rfc1341/7_2_Multipart.html 得知

Thus, a typical multipart Content-Type header field might look like this:

     Content-Type: multipart/mixed; 
          boundary=gc0p4Jq0M2Yt08jU534c0p
 

This indicates that the entity consists of several parts, each itself with a structure that is syntactically identical to an RFC 822 message, except that the header area might be completely empty, and that the parts are each preceded by the line

     --gc0p4Jq0M2Yt08jU534c0p
 

The encapsulation boundary following the last body part is a distinguished delimiter that indicates that no further body parts will follow. Such a delimiter is identical to the previous delimiters, with the addition of two more hyphens at the end of the line:

     --gc0p4Jq0M2Yt08jU534c0p--