Uploading PNG File (HTTP POST) with C++ Winsock API - c++

Question

I'm trying to upload a PNG file through Winsock2 HTTP Post. Here's my request string:
boundary = "-----rueldotme";
request += "POST " + uri + " HTTP/1.1\r\n";
request += "Host: " + hostname + "\r\n";
request += "User-Agent: " + UserAgent + "\r\n";
request += "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\n";
request += "Accept-Language: en-us,en;q=0.5\r\n";
request += "Accept-Encoding: gzip,deflate\r\n";
request += "Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7\r\n";
request += "Keep-Alive: 115\r\n";
request += "Connection: keep-alive\r\n";
request += "Content-Length: " + fileSize + "\r\n";
request += "Content-Type: multipart/form-data, boundary=" + boundary + "\r\n";
request += "\r\n";
request += "--" + boundary + "\r\n";
request += "Content-Disposition: form-data; name=\"filename\"; filename=\"" + fileName + "\"\r\n";
request += "Content-Type: image/png; charset=binary\r\n";
request += "Content-Transfer-Encoding: binary\r\n";
request += "\r\n";
request += "%s\r\n";
request += "\r\n";
The connection is OK, no errors and such, the fileCon by the way is from ReadFile(). And there's no error code. The number of bytes read is the same as the output of GetFileSize(). I tried displaying the contents of fileCon but only gave me this:
Don't mind the title "Error" (I set it).
Also, the request takes ages to complete, and gives me a blank response. Yep, blank with no HTTP headers. Am I doing the request right? Should I really have to include the file contents at the POST data?
Thanks in advance.
EDIT: The PNG size is about 256KB. I'm in a 1mbps connection.
EDIT: Sorry if the information was insufficient. Anyway, here's what I did lately:
int flz;
char bdata[BSIZE];
DWORD dwe, bytesRead = 0;
HANDLE fh = CreateFile(fileName.c_str(), GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
LPVOID fbuff = NULL;
flz = GetFileSize(fh, NULL);
fbuff = malloc(flz);
ReadFile(fh, fbuff, flz, &bytesRead, NULL));
...
sprintf_s(bdata, BSIZE, request.c_str(), reinterpret_cast<char *>(fbuff)); //BSIZE = 1024
...
send(sock, bdata, std::strlen(bdata), 0);

Answer 1

Not enough information to solve the problem, so I'll give a meta-answer instead:
Use a packet sniffer (e.g., wireshark) to check exactly what data is actually being sent and received. This will let you verify that the request is as it should be, and that the "blank response" you're getting really is blank.
One wild stab in the dark:
You haven't included any variable declarations in your code snippet, so I don't know what type "fileCon" is, but don't forget that the PNG data is likely to contain null bytes, which will mess up a default conversion from a char* to a std::string.
Edit:
Your modification contains the same bug that the std::string based version had, namely, that the PNG data is likely to contain null bytes. Perhaps this code will explain more clearly:
const char* data = "Hello\0world."; // some data that contains a null byte
std::string dataStr(data);
std::cout << dataStr << "\n"; // will print "Hello".
std::cout << dataStr.size() << "\n"; // will print "5"
char buf[512];
sprintf_s(buf, sizeof(buf), "Data: %s\n", data);
std::cout << buf; // will print "Data: Hello"
Both the conversion to std::string and formatting with sprintf will interpret the null byte as being the end of the data, and so the rest of the original data ("world.") will never be used.