text: //
  // Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail dot com)
  //
  // Distributed under the Boost Software License, Version 1.0. (See accompanying
  // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  //
  // Official repository: https://github.com/boostorg/beast
  //
  
  //------------------------------------------------------------------------------
  //
  // Example: WebSocket SSL client, coroutine
  //
  //------------------------------------------------------------------------------
  
  #include "example/common/root_certificates.hpp"
  
  #include <boost/beast/core.hpp>
  #include <boost/beast/ssl.hpp>
  #include <boost/beast/websocket.hpp>
  #include <boost/beast/websocket/ssl.hpp>
  #include <boost/asio/spawn.hpp>
  #include <cstdlib>
  #include <functional>
  #include <iostream>
  #include <string>
  
  namespace beast = boost::beast;         // from <boost/beast.hpp>
  namespace http = beast::http;           // from <boost/beast/http.hpp>
  namespace websocket = beast::websocket; // from <boost/beast/websocket.hpp>
  namespace net = boost::asio;            // from <boost/asio.hpp>
  namespace ssl = boost::asio::ssl;       // from <boost/asio/ssl.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";
  }
  
  // Sends a WebSocket message and prints the response
  void
  do_session(
      std::string const& host,
      std::string const& port,
      std::string const& text,
      net::io_context& ioc,
      ssl::context& ctx,
      net::yield_context yield)
  {
      beast::error_code ec;
  
      // These objects perform our I/O
      tcp::resolver resolver(ioc);
      websocket::stream<
          beast::ssl_stream<beast::tcp_stream>> ws(ioc, ctx);
  
      // Look up the domain name
      auto const results = resolver.async_resolve(host, port, yield[ec]);
      if(ec)
          return fail(ec, "resolve");
  
      // Set a timeout on the operation
      beast::get_lowest_layer(ws).expires_after(std::chrono::seconds(30));
  
      // Make the connection on the IP address we get from a lookup
      beast::get_lowest_layer(ws).async_connect(results, yield[ec]);
      if(ec)
          return fail(ec, "connect");
  
      // Set a timeout on the operation
      beast::get_lowest_layer(ws).expires_after(std::chrono::seconds(30));
  
      // Set a decorator to change the User-Agent of the handshake
      ws.set_option(websocket::stream_base::decorator(
          [](websocket::request_type& req)
          {
              req.set(http::field::user_agent,
                  std::string(BOOST_BEAST_VERSION_STRING) +
                      " websocket-client-coro");
          }));
  
      // Perform the SSL handshake
      ws.next_layer().async_handshake(ssl::stream_base::client, yield[ec]);
      if(ec)
          return fail(ec, "ssl_handshake");
  
      // Turn off the timeout on the tcp_stream, because
      // the websocket stream has its own timeout system.
      beast::get_lowest_layer(ws).expires_never();
  
      // Set suggested timeout settings for the websocket
      ws.set_option(
          websocket::stream_base::timeout::suggested(
              beast::role_type::client));
  
      // Perform the websocket handshake
      ws.async_handshake(host, "/", yield[ec]);
      if(ec)
          return fail(ec, "handshake");
  
      // Send the message
      ws.async_write(net::buffer(std::string(text)), yield[ec]);
      if(ec)
          return fail(ec, "write");
  
      // This buffer will hold the incoming message
      beast::flat_buffer buffer;
  
      // Read a message into our buffer
      ws.async_read(buffer, yield[ec]);
      if(ec)
          return fail(ec, "read");
  
      // Close the WebSocket connection
      ws.async_close(websocket::close_code::normal, yield[ec]);
      if(ec)
          return fail(ec, "close");
  
      // If we get here then the connection is closed gracefully
  
      // The make_printable() function helps print a ConstBufferSequence
      std::cout << beast::make_printable(buffer.data()) << std::endl;
  }
  
  //------------------------------------------------------------------------------
  
  int main(int argc, char** argv)
  {
      // Check command line arguments.
      if(argc != 4)
      {
          std::cerr <<
              "Usage: websocket-client-coro-ssl <host> <port> <text>\n" <<
              "Example:\n" <<
              "    websocket-client-coro-ssl echo.websocket.org 443 \"Hello, world!\"\n";
          return EXIT_FAILURE;
      }
      auto const host = argv[1];
      auto const port = argv[2];
      auto const text = argv[3];
  
      // The io_context is required for all I/O
      net::io_context ioc;
  
      // The SSL context is required, and holds certificates
      ssl::context ctx{ssl::context::tlsv12_client};
  
      // This holds the root certificate used for verification
      load_root_certificates(ctx);
  
      // Launch the asynchronous operation
      boost::asio::spawn(ioc, std::bind(
          &do_session,
          std::string(host),
          std::string(port),
          std::string(text),
          std::ref(ioc),
          std::ref(ctx),
          std::placeholders::_1));
  
      // Run the I/O service. The call will return when
      // the socket is closed.
      ioc.run();
  
      return EXIT_SUCCESS;
  }
  