Unable to receive HTTP response body C++ - c++

Question

First, here is the C++ code I am using to make HTTP POST requests. It links to ws2_32.lib.
int POST_TEST(std::string URL, std::string DATA)
{
//**************************************************
std::string TEXT = "";
std::string DIRECTORY = URL.substr(URL.find(".com") + std::string(".com").length());
std::string HOST = URL.substr(0, URL.find(".com", std::string(".com").length())) + ".com";
std::string REQ = "POST " + DIRECTORY + " HTTP/1.1\r\nContent-Length: " + to_string(DATA.length()) + "\r\nAccept-Language: en-US,en;q=0.5\r\nAccept-Encoding: gzip, deflate\r\nHost: " + HOST + "\r\nAccept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\nUser-Agent: Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:44.0) Gecko/20100101 Firefox/44.0\r\nConnection: keep-alive\r\nContent-Type: application/x-www-form-urlencoded\r\n\r\n" + DATA;
const char * REQUEST = REQ.c_str();
//**************************************************
WSADATA wsaData;
if(WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)
return 1;
SOCKET Socket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
struct hostent *host = gethostbyname(HOST.c_str());
SOCKADDR_IN SockAddr;
SockAddr.sin_port = htons(80);
SockAddr.sin_family = AF_INET;
SockAddr.sin_addr.s_addr = *((unsigned long*)host->h_addr);
if(connect(Socket,(SOCKADDR*)(&SockAddr), sizeof(SockAddr)) != 0)
return 1;
send(Socket, REQUEST, strlen(REQUEST), 0);
char buffer[1000];
int nDataLength;
while((nDataLength = recv(Socket, buffer, 1000, 0)) > 0)
{
int i = 0;
while(buffer[i] >= 32 || buffer[i] == '\n' || buffer[i] == '\r')
{
TEXT += buffer[i];
i++;
}
}
closesocket(Socket);
WSACleanup();
MessageBoxA(NULL, TEXT.c_str(), "HTTP Response", MB_OK);
return 0;
}
POST_TEST("blah.com/a.php", "a=blah");
The code works well, but I am receiving only the HTTP Header response, and I don't see the response BODY. Making the POST request using Python to the same php page allows me to see the response body just fine. I'm not sure if I'm misunderstanding something, or there's an error in my code.
The PHP page I'm POSTing to is located on my own server. The PHP echoes some text, but I do not see that in the response. This is the response I get:
HTTP/1.1 200 OK
Server: nginx/1.8.1
Date: Fri, 08 Apr 2016 02:10:14 GMT
Content-Type: text/html
Content-Length: 286
Connection: keep-alive
Vary: Accept-Encoding
Content-Encoding: gzip
How would I be able to see the entire response?

Answer 1

There are two bugs in the shown code.
It doesn't check the return value from send(). send() does not guarantee that the number of bytes requested to be sent was actually sent. The return value from send() may return an indication that fewer bytes were written than what were requested. It is your responsibility to check that, and try again to send() the remaining bytes.
The logic for reading and collecting the response is wrong. recv() tells you how many bytes were received. This is ignored completely. Instead, the code scans the read buffer until it sees a control character as a byte.
Note that your HTTP response indicates that you're getting raw, gzip-compressed binary data. It is fairly likely that within the first few bytes of the actual response there are going to be some binary bytes that correspond to ASCII control characters, in value. Your loop will come to a screeching halt at that point.
Even if you were expecting a plain text response, this logic would still be wrong. It is the return value from recv() that tells you how many bytes were received, and nothing else.