ASIO (Boost) SSL网络传输

Question

我从不同的Boost源中收集了这段代码，尝试创建连接到主机并通过SSL下载根页面/文件的东西。程序运行，但返回一个空的回复。有人能建议一下为什么会出现这种情况，并提出改进建议吗？链接与-l pthread -l ssl -l加密。

//
// client.cpp
// ~~~~~~~~~~
//
// Copyright (c) 2003-2015 Christopher M. Kohlhoff (chris at kohlhoff 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)
//

#include <iostream>
#include <asio.hpp>
#include <asio/ssl.hpp>
#include <functional>

static const char *HOSTNAME { "google.com" };
static const char *HOSTPORT { "https" };
std::string file { "/" };
std::string request { 
  "GET " + file + " " 
  + "HTTP/1.1\r\nHost: " + std::string(HOSTNAME) + "\r\n\r\n" };

enum { max_length = 1024 };

class Client
{
  asio::ssl::stream<asio::ip::tcp::socket> ssock;
  char reply[max_length];
  std::size_t bytes_transferred;
  std::error_code ec;
  public:
  Client(asio::io_service &io_service, asio::ssl::context &context, asio::ip::tcp::resolver::iterator endpoint_iterator) : 
    ssock(io_service, context)
  {
    auto handle_connect { std::bind(&Client::handle_handshake, this, ec) };
    asio::async_connect(ssock.lowest_layer(), endpoint_iterator, handle_connect);
  }
  
  void handle_connect(const std::error_code &ec)
  {
    if (!ec)
    {
      auto handle_handshake { std::bind(&Client::handle_handshake, this, ec) };
      ssock.async_handshake(asio::ssl::stream_base::client, handle_handshake);
    }
    else std::cout << "Connect failed: " << ec.message() << "\n";
  }

  void handle_handshake(const std::error_code &ec)
  {
    if (!ec)
    {
      std::cout << request << std::endl;
      auto handle_write { std::bind(&Client::handle_write, this, ec, bytes_transferred) };
      asio::async_write(ssock, asio::buffer(request), handle_write);
    }
    else std::cout << "Handshake failed: " << ec.message() << "\n";
  }

  void handle_write(const std::error_code &ec, std::size_t bytes_transferred)
  {
    if (!ec)
    {
      auto handle_read { std::bind(&Client::handle_read, this, ec, bytes_transferred) };
      asio::async_read(ssock, asio::buffer(reply, bytes_transferred), handle_read);
    }
    else std::cout << "Write failed: " << ec.message() << "\n";
  }

  void handle_read(const std::error_code &ec, std::size_t bytes_transferred)
  {
    if (!ec)
    {
      std::cout << "Reply: ";
      std::cout.write(reply, bytes_transferred);
      std::cout << "\n";
    }
    else std::cout << "Read failed: " << ec.message() << "\n";
  }
};

int main(int argc, char* argv[])
{
  try
  {
    asio::io_service io_service;
    asio::ip::tcp::resolver resolver(io_service);
    asio::ip::tcp::resolver::query query(HOSTNAME, HOSTPORT);
    asio::ip::tcp::resolver::iterator iterator = resolver.resolve(query);
    asio::ssl::context ctx(asio::ssl::context::sslv23);
    Client client(io_service, ctx, iterator);
    io_service.run();
  }
  catch (std::exception& e)
  {
    std::cerr << "Exception: " << e.what() << "\n";
  }

  return 0;
}

我认为问题出在这些回调函数上。回调中的操作本身是正确的，因为它们直接取自示例。有没有更好的方法通过使用Lambdas进行回调来重写？我不喜欢这些回调被绑定的方式。

Answer 1

auto handle_connect { std::bind(&Client::handle_handshake, this, ec) };

在构造函数中应该是：

auto handle_connect { std::bind(&Client::handle_connect, this, ec) };