C++ Networking: Request method POST - c++

Question

I'm trying to communicate with some server. To get username (with permissions), I need to do something like registration: HTTP request method POST send json-like body containing {"devicetype": "devicename"}. O tried to do it with ASIO library.
asio::error_code ec;
asio::io_context context;
asio::ip::tcp::endpoint endpoint(asio::ip::make_address("ipAddress", ec), 80);
asio::ip::tcp::socket socket(context);
if (!ec)
{
std::cout << "Succesfully connected\n";
}
else
{
std::cout << "Failed to connect to address: \n" << ec.message() << std::endl;
}
if (socket.is_open())
{
std::string sRequest =
"POST /api HTTP/1.1\r\n"
"Host: ipAddress \r\n"
"Body: {\"devicetype\": \"devicename\"}"
"Connection: close\r\n\r\n";
socket.write_some(asio::buffer(sRequest.data(), sRequest.size()), ec);
/*Reading received message and getting error message from server*/
}
Error says: "invalid/missing parameters in body". The parameters are correct. The problem is probably with message formatting I am sending (sRequest). How can I specify json body to message?
Thanks for help.

Answer 1

What you have shown is not a properly formatted HTTP request. There is no Body header in HTTP. The JSON data needs to go after the \r\n\r\n that terminates the headers. And you need to add Content-Type and Content-Length headers so the server knows what kind of data you are posting and how large it is.
Try this instead:
std::string json = "{\"devicetype\": \"devicename\"}";
std::string sRequest =
"POST /api HTTP/1.1\r\n"
"Host: ipAddress\r\n"
"Content-Type: application/json\r\n"
"Content-Length: " + std::to_string(json.size()) + "\r\n"
"Connection: close\r\n\r\n" + json;