Sending POST multipart/form-data request using c++ code - c++

Question

I am trying to write a client, which will connect to a server and make a HTTP POST multipart/form-data request. Please go through following code. With this code, I am not getting any error response.
I am able to get some response, but not exactly what I expet.
With this code I am able to access the URL, but I think server is not reading the parameters (payload).
I am not sure whether I am passing an appropriate payload.
Please help me to write an appropriate payload. Thanks.
void BuildHTTPRequest::BuildHeader1(stringstream &hdr,string payload)
{
hdr << "POST /home/one/user/send_event HTTP/1.1\r\n";
hdr << "Host:host.domain.com\r\n";
hdr << "Port:80\r\n";
hdr << "Content-Type:multipart/form-data; boundary=463762444806\r\n";
hdr << "Content-Length:" << payload.size() << "\r\n";
hdr << "\r\n";
hdr << payload;
}
void BuildHTTPRequest::BuildPayload1(string *payload)
{
(*payload).append("Content-Disposition: form-data; name=\"interface_version\"\r\n\r\n");
(*payload).append("01.0.01\r\n");
(*payload).append("-----------------------------463762444806\r\n");
(*payload).append("Content-Disposition: form-data; name=\"terminal_id\"\r\n\r\n");
(*payload).append("1\r\n");
(*payload).append("-----------------------------463762444806\r\n");
(*payload).append("Content-Disposition: form-data; name=\"device\"\r\n\r\n");
(*payload).append("display\r\n");
(*payload).append("-----------------------------463762444806\r\n");
(*payload).append("Content-Disposition: form-data; name=\"start_session\"\r\n\r\n");
(*payload).append("true\r\n");
(*payload).append("-----------------------------463762444806\r\n");
(*payload).append("Content-Disposition: form-data; name=\"first_contact\"\r\n\r\n");
(*payload).append("true\r\n");
(*payload).append("-----------------------------463762444806--\r\n\r\n");
}

Answer 1

You should also have a boundary delimiter before the first payload data and since you aren't putting any preamble before the multipart data, you need 2 CRLF between your request headers and your payload.
The requirement that the encapsulation boundary begins with a CRLF
implies that the body of a multipart entity must itself begin with a
CRLF before the first encapsulation line -- that is, if the "preamble"
area is not used, the entity headers must be followed by TWO CRLFs.
This is indeed how such entities should be composed.
Also, why do use more than 2 hyphens before your boundary value for the delimiter ?
Specs says:
The Content-Type field for multipart entities requires one parameter,
"boundary", which is used to specify the encapsulation boundary. The
encapsulation boundary is defined as a line consisting entirely of two
hyphen characters ("-", decimal code 45) followed by the boundary
parameter value from the Content-Type header field.
...
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
Try this instead:
void BuildHTTPRequest::BuildPayload1(string *payload)
{
(*payload).append("\r\n--463762444806\r\n");
(*payload).append("Content-Disposition: form-data; name=\"interface_version\"\r\n\r\n");
(*payload).append("01.0.01\r\n");
(*payload).append("--463762444806\r\n");
(*payload).append("Content-Disposition: form-data; name=\"terminal_id\"\r\n\r\n");
(*payload).append("1\r\n");
(*payload).append("--463762444806\r\n");
(*payload).append("Content-Disposition: form-data; name=\"device\"\r\n\r\n");
(*payload).append("display\r\n");
(*payload).append("--463762444806\r\n");
(*payload).append("Content-Disposition: form-data; name=\"start_session\"\r\n\r\n");
(*payload).append("true\r\n");
(*payload).append("--463762444806\r\n");
(*payload).append("Content-Disposition: form-data; name=\"first_contact\"\r\n\r\n");
(*payload).append("true\r\n");
(*payload).append("--463762444806--\r\n\r\n");
}