Example of multipart/form-data

2019-01-04 09:36发布

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I am wondering if anyone can share with me an example of multipart/form-data that contains:

  1. Some form parameters
  2. Multiple files

2条回答
乱世女痞
2楼-- · 2019-01-04 09:40

Many thanks to @Ciro Santilli answer! I found that his choice for boundary is quite "unhappy" because all of thoose hyphens: in fact, as @Fake Name commented, when you are using your boundary inside request it comes with two more hyphens on front:

Example:

POST / HTTP/1.1
HOST: host.example.com
Cookie: some_cookies...
Connection: Keep-Alive
Content-Type: multipart/form-data; boundary=12345

--12345
Content-Disposition: form-data; name="sometext"

some text that you wrote in your html form ...
--12345
Content-Disposition: form-data; name="name_of_post_request" filename="filename.xyz"

content of filename.xyz that you upload in your form with input[type=file]
--12345
Content-Disposition: form-data; name="image" filename="picture_of_sunset.jpg"

content of picture_of_sunset.jpg ...
--12345--

I found on this w3.org page that is possible to incapsulate multipart/mixed header in a multipart/form-data, simply choosing another boundary string inside multipart/mixed and using that one to incapsulate data. At the end, you must "close" all boundary used in FILO order to close the POST request (like:

POST / HTTP/1.1
...
Content-Type: multipart/form-data; boundary=12345

--12345
Content-Disposition: form-data; name="sometext"

some text sent via post...
--12345
Content-Disposition: form-data; name="files"
Content-Type: multipart/mixed; boundary=abcde

--abcde
Content-Disposition: file; file="picture.jpg"

content of jpg...
--abcde
Content-Disposition: file; file="test.py"

content of test.py file ....
--abcde--
--12345--

Take a look at the link above.

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放我归山
3楼-- · 2019-01-04 09:50

EDIT: I am maintaining a similar, but more in-depth answer at: https://stackoverflow.com/a/28380690/895245

To see exactly what is happening, use nc -l or an ECHO server and an user agent like a browser or cURL.

Save the form to an .html file:

<form action="http://localhost:8000" method="post" enctype="multipart/form-data">
  <p><input type="text" name="text" value="text default">
  <p><input type="file" name="file1">
  <p><input type="file" name="file2">
  <p><button type="submit">Submit</button>
</form>

Create files to upload:

echo 'Content of a.txt.' > a.txt
echo '<!DOCTYPE html><title>Content of a.html.</title>' > a.html

Run:

nc -l localhost 8000

Open the HTML on your browser, select the files and click on submit and check the terminal.

nc prints the request received. Firefox sent:

POST / HTTP/1.1
Host: localhost:8000
User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:29.0) Gecko/20100101 Firefox/29.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Cookie: __atuvc=34%7C7; permanent=0; _gitlab_session=226ad8a0be43681acf38c2fab9497240; __profilin=p%3Dt; request_method=GET
Connection: keep-alive
Content-Type: multipart/form-data; boundary=---------------------------9051914041544843365972754266
Content-Length: 554

-----------------------------9051914041544843365972754266
Content-Disposition: form-data; name="text"

text default
-----------------------------9051914041544843365972754266
Content-Disposition: form-data; name="file1"; filename="a.txt"
Content-Type: text/plain

Content of a.txt.

-----------------------------9051914041544843365972754266
Content-Disposition: form-data; name="file2"; filename="a.html"
Content-Type: text/html

<!DOCTYPE html><title>Content of a.html.</title>

-----------------------------9051914041544843365972754266--

Aternativelly, cURL should send the same POST request as your a browser form:

nc -l localhost 8000
curl -F "text=default" -F "file1=@a.html" -F "file1=@a.txt" localhost:8000

You can do multiple tests with:

while true; do printf '' | nc -l localhost 8000; done
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