Boost Beast async rest client : async_resolve - resolve: Host not found (authoritative) - rest

Question

I have the async boost rest client code. I am able to compile and run this code using Cygwin on Windows.
#include <boost/beast/core.hpp>
#include <boost/beast/http.hpp>
#include <boost/beast/version.hpp>
#include <boost/asio/connect.hpp>
#include <boost/asio/ip/tcp.hpp>
#include <cstdlib>
#include <functional>
#include <iostream>
#include <memory>
#include <string>
using tcp = boost::asio::ip::tcp; // from <boost/asio/ip/tcp.hpp>
namespace http = boost::beast::http; // from <boost/beast/http.hpp>
void
fail(boost::system::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_;
tcp::socket socket_;
boost::beast::flat_buffer buffer_; // (Must persist between reads)
http::request<http::empty_body> req_;
http::response<http::string_body> res_;
public:
// Resolver and socket require an io_context
explicit
session(boost::asio::io_context& ioc)
: resolver_(ioc)
, socket_(ioc)
{
}
// Start the asynchronous operation
void
run(char const* host, char const* port, char const* target, int version)
{
// Set up an HTTP GET request message
req_.version(version);
req_.method(http::verb::get);
req_.target(target);
req_.set(http::field::host, host);
req_.set(http::field::user_agent, BOOST_BEAST_VERSION_STRING);
// Look up the domain name
resolver_.async_resolve(host, port,std::bind( &session::on_resolve, shared_from_this(), std::placeholders::_1, std::placeholders::_2));
}
void
on_resolve( boost::system::error_code ec, tcp::resolver::results_type results)
{
if(ec) {
return fail(ec, "resolve");
}
// Make the connection on the IP address we get from a lookup
boost::asio::async_connect(socket_,results.begin(),results.end(),std::bind(&session::on_connect,shared_from_this(), std::placeholders::_1));
}
void
on_connect(boost::system::error_code ec)
{
if(ec) {
return fail(ec, "connect");
}
// Send the HTTP request to the remote host
http::async_write(socket_, req_,std::bind(&session::on_write, shared_from_this(), std::placeholders::_1, std::placeholders::_2));
}
void
on_write( boost::system::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(socket_, buffer_, res_, std::bind( &session::on_read, shared_from_this(), std::placeholders::_1, std::placeholders::_2));
}
void
on_read(boost::system::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
socket_.shutdown(tcp::socket::shutdown_both, ec);
// not_connected happens sometimes so don't bother reporting it.
if(ec && ec != boost::system::errc::not_connected) {
return fail(ec, "shutdown");
}
// If we get here then the connection is closed gracefully
}
};
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
boost::asio::io_context ioc;
// Launch the asynchronous operation
std::make_shared<session>(ioc)->run(host, port, target, version);
// Run the I/O service. The call will return when
// the get operation is complete.
ioc.run();
return EXIT_SUCCESS;
}
I have a python REST Server that runs waiting for requests from this client.
#!flask/bin/python
from flask import Flask, jsonify
app = Flask(__name__)
tasks = [
{
'id': 1,
'title': u'Buy groceries',
'description': u'Milk, Cheese, Pizza, Fruit, Tylenol',
'done': False
},
{
'id': 2,
'title': u'Learn Python',
'description': u'Need to find a good Python tutorial on the web',
'done': False
}
]
#app.route('/todo/api/v1.0/tasks', methods=['GET'])
def get_tasks():
return jsonify({'tasks': tasks})
if __name__ == '__main__':
app.run(host='0.0.0.0',debug=True)
I am able to run this server. The output is shown below.
* Serving Flask app 'RESTServer' (lazy loading)
* Environment: production
WARNING: This is a development server. Do not use it in a production deployme
nt.
Use a production WSGI server instead.
* Debug mode: on
* Restarting with stat
* Debugger is active!
* Debugger PIN: 409-562-797
* Running on all addresses.
WARNING: This is a development server. Do not use it in a production deployme
nt.
* Running on http://192.168.1.104:5000/ (Press CTRL+C to quit)
However when I run the REST Client, as below
rest_client.exe http://192.168.1.104 5000 /todo/api/v1.0/tasks
I get the following error
resolve: Host not found (authoritative)

Answer 1

The program expects separate arguments. It even gives you usage instructions:
Usage: http-client-async <host> <port> <target> [<HTTP version: 1.0 or 1.1(default)>]
Example:
http-client-async www.example.com 80 /
http-client-async www.example.com 80 / 1.0
So it looks like you AT LEAST want to remove http://