Send POST data via HttpOpenRequestA - c++

Question

I'm trying to send my PC Name to my local server and save it in a file.
There is my code:
#include <stdio.h>
#include <windows.h>
#include <iostream>
#include <fstream>
#include <string>
#include <string.h>
#include <cstring>
#include <Lmcons.h>
#include <unistd.h>
#include <stdlib.h>
#include <WinInet.h>
#include <bits/stdc++.h>
#pragma comment( lib,"Wininet.lib")
using namespace std;
int main() {
TCHAR name [ UNLEN + 1 ];
DWORD size = UNLEN + 1;
static CHAR hdrs[] = "Content-Type: application/x-www-form-urlencoded";
if (GetUserName( (TCHAR*)name, &size ));
static CHAR frmdata[] = "data=", name;
HINTERNET hSession = InternetOpenA("http generic", INTERNET_OPEN_TYPE_PRECONFIG, NULL, NULL, 0);
HINTERNET hConnect = InternetConnect(hSession, "127.0.0.1", INTERNET_DEFAULT_HTTP_PORT, NULL, NULL, INTERNET_SERVICE_HTTP, 0, 1);
HINTERNET hRequest = HttpOpenRequestA(hConnect, "POST", "/test/index.php", NULL, NULL, NULL, 0, 1);
HttpSendRequestA(hRequest, hdrs, strlen(hdrs), frmdata, strlen(frmdata));
}
I've tried use static CHAR frmdata[] = "data=" + name; also but not works.
This is the error that I receive:
error: invalid operands of types 'const char [6]' and 'TCHAR [257] {aka char [257]}' to binary 'operator+'|

Answer 1

You can't concatenate char[] arrays like you are trying to do. Allocate a separate buffer of sufficient size and copy the input strings into it, eg:
#include <windows.h>
#include <Lmcons.h>
#include <WinInet.h>
#include <cstring>
//#include <cstdio>
using namespace std;
#pragma comment( lib, "Wininet.lib")
int main()
{
static char hdrs[] = "Content-Type: application/x-www-form-urlencoded";
char name[UNLEN + 1] = {};
DWORD size = UNLEN + 1;
GetUserNameA(name, &size);
char frmdata[5 + UNLEN + 1] = {};
strcpy(frmdata, "data=");
strcat(frmdata, name);
// alternatively:
// sprintf(frmdata, "data=%s", name);
HINTERNET hSession = InternetOpenA("http generic", INTERNET_OPEN_TYPE_PRECONFIG, NULL, NULL, 0);
if (!hSession) {
// error handling...
}
HINTERNET hConnect = InternetConnectA(hSession, "127.0.0.1", INTERNET_DEFAULT_HTTP_PORT, NULL, NULL, INTERNET_SERVICE_HTTP, 0, 1);
if (!hConnect) {
// error handling...
}
HINTERNET hRequest = HttpOpenRequestA(hConnect, "POST", "/test/index.php", NULL, NULL, NULL, 0, 1);
if (!hRequest) {
// error handling...
}
if (!HttpSendRequestA(hRequest, hdrs, strlen(hdrs), frmdata, strlen(frmdata))) {
// error handling...
}
InternetCloseHandle(hRequest);
InternetCloseHandle(hConnect);
InternetCloseHandle(hSession);
return 0;
}
Alternatively, you can use a single buffer, just make it larger, and have GetUserNameA() populate a portion of it, then you don't need to make a copy afterwards, eg:
int main()
{
...
char frmdata[5 + UNLEN + 1] = "data=";
DWORD size = UNLEN + 1;
GetUserNameA(&frmdata[5], &size);
...
}

Answer 2

You need to concatenate, which std::string can do for you. You should also use the same base character type to avoid the need for additional conversions.
char name [ UNLEN + 1 ];
DWORD size = UNLEN + 1;
GetUserNameA( name, &size );
std::string frmdata;
frmdata += "data=";
frmdata += name;
...
HttpSendRequestA(hRequest, hdrs, strlen(hdrs), frmdata.data(), (DWORD)frmdata.size());
In case you want to transport unicode data (use std::wstring in that case) you will need to convert your data string to proper utf-8 (lookup WideCharToMultiByte).