boost beast sample to send post - post

Question

I'm getting the following response and I don't know how to identify the problem. Fiddler doesn't capture anything so I believe the request is not being sent out.
HTTP/1.1 411 Length Required
Content-Type: text/html; charset=us-ascii
Server: Microsoft-HTTPAPI/2.0
Date: Wed, 22 May 2019 11:15:04 GMT
Connection: close
Content-Length: 344
I've attempted to follow the other examples I've found, but it seems setting the body no longer compiles.
// error C2679: binary '=': no operator found which takes a right-hand operand of type 'const char *' (or there is no acceptable conversion)
req_.body() = "test";
I'm using Visual Studio 2017 compiled for x64 with Boost linked as DLLs. I started with the beast samples and got "GET" to work perfectly for me. I'm having problems getting "POST" to work from the beast client
`
//
// Example: HTTP client, asynchronous
//
// Quickly add boost DLLs with: https://www.nuget.org/packages/boost-vc141/
#include <boost/beast/core.hpp>
#include <boost/beast/http.hpp>
#include <boost/beast/version.hpp>
#include <boost/asio/strand.hpp>
#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/json_parser.hpp>
#include <boost/lexical_cast.hpp>
#include <cstdlib>
#include <functional>
#include <iostream>
#include <memory>
#include <string>
namespace beast = boost::beast; // from <boost/beast.hpp>
namespace http = beast::http; // from <boost/beast/http.hpp>
namespace net = boost::asio; // from <boost/asio.hpp>
using tcp = boost::asio::ip::tcp; // from <boost/asio/ip/tcp.hpp>
// Report a failure
void
fail(beast::error_code ec, char const* what)
{
std::cerr << what << ": " << ec.message() << "\n";
}
// Performs an HTTP GET and prints the response
class session : public std::enable_shared_from_this<session>
{
tcp::resolver resolver_;
beast::tcp_stream stream_;
beast::flat_buffer buffer_; // (Must persist between reads)
http::request<http::dynamic_body> req_;
http::response<http::string_body> res_;
public:
// Objects are constructed with a strand to
// ensure that handlers do not execute concurrently.
explicit
session(net::io_context& ioc)
: resolver_(net::make_strand(ioc))
, stream_(net::make_strand(ioc))
{
}
// Start the asynchronous operation
void
run(
char const* host,
char const* port,
char const* target,
char const* body,
int version)
{
// Set up an HTTP POST request message
req_.version(version);
req_.method(http::verb::post);
req_.target(target);
req_.set(http::field::host, host);
req_.set(http::field::user_agent, BOOST_BEAST_VERSION_STRING);
req_.set(http::field::content_length, boost::lexical_cast<std::string>(strlen(body)));
req_.set(http::field::body, body);
req_.prepare_payload();
// following line doesn't compile:
// error C2679: binary '=': no operator found which takes a right-hand operand of type 'const char *' (or there is no acceptable conversion)
//req_.body() = body;
// Look up the domain name
resolver_.async_resolve(
host,
port,
beast::bind_front_handler(
&session::on_resolve,
shared_from_this()));
}
void
on_resolve(
beast::error_code ec,
tcp::resolver::results_type results)
{
if (ec)
return fail(ec, "resolve");
// Set a timeout on the operation
stream_.expires_after(std::chrono::seconds(30));
// Make the connection on the IP address we get from a lookup
stream_.async_connect(
results,
beast::bind_front_handler(
&session::on_connect,
shared_from_this()));
}
void
on_connect(beast::error_code ec, tcp::resolver::results_type::endpoint_type)
{
if (ec)
return fail(ec, "connect");
// Set a timeout on the operation
stream_.expires_after(std::chrono::seconds(30));
// Send the HTTP request to the remote host
http::async_write(stream_, req_,
beast::bind_front_handler(
&session::on_write,
shared_from_this()));
}
void
on_write(
beast::error_code ec,
std::size_t bytes_transferred)
{
boost::ignore_unused(bytes_transferred);
if (ec)
return fail(ec, "write");
// Receive the HTTP response
http::async_read(stream_, buffer_, res_,
beast::bind_front_handler(
&session::on_read,
shared_from_this()));
}
void
on_read(
beast::error_code ec,
std::size_t bytes_transferred)
{
boost::ignore_unused(bytes_transferred);
if (ec)
return fail(ec, "read");
// Write the message to standard out
std::cout << res_ << std::endl;
// Gracefully close the socket
stream_.socket().shutdown(tcp::socket::shutdown_both, ec);
// not_connected happens sometimes so don't bother reporting it.
if (ec && ec != beast::errc::not_connected)
return fail(ec, "shutdown");
// If we get here then the connection is closed gracefully
}
};
std::string create_body()
{
boost::property_tree::ptree tree;
tree.put("foo", "bar");
std::basic_stringstream<char> jsonStream;
boost::property_tree::json_parser::write_json(jsonStream, tree, false);
return jsonStream.str();
}
int main(int argc, char** argv)
{
// Check command line arguments.
if (argc != 4 && argc != 5)
{
std::cerr <<
"Usage: http-client-async <host> <port> <target> [<HTTP version: 1.0 or 1.1(default)>]\n" <<
"Example:\n" <<
" http-client-async www.example.com 80 /\n" <<
" http-client-async www.example.com 80 / 1.0\n";
return EXIT_FAILURE;
}
auto const host = argv[1];
auto const port = argv[2];
auto const target = argv[3];
int version = argc == 5 && !std::strcmp("1.0", argv[4]) ? 10 : 11;
// The io_context is required for all I/O
net::io_context ioc;
// Launch the asynchronous operation
std::make_shared<session>(ioc)->run(host, port, target, create_body().c_str(), version);
// Run the I/O service. The call will return when
// the get operation is complete.
ioc.run();
return EXIT_SUCCESS;
}
`
How do I see what beast is generating as the packet to be sent?
How do I fix the compilation error attempting to set the body as shown in other posts: request.body() = "bodytext";
Can someone provide a sample beast client & server that uses post?

Answer 1

In the operator= for the body is not available because your request is declared with template http::dynamic_body:
http::request<http::dynamic_body> req_;
Change your template argument to http::string_body and the operator= will work
http::response<http::string_body> req_;
It will be possible to compile the code
req_.body() = body;
I tested it under CentOS7.