logo标签列表

无法实现 boost::asio::ssl::stream<boost::asio::ip::tcp::socket> 重新连接服务器

c++socketssslboostboost-asio
3

我需要实现一个类来处理连接到ssl服务器的功能，其基本上是按照这个实现的。然而，它没有重新连接功能。因此，我对其进行了修改：

boost::asio::ssl::stream<boost::asio::ip::tcp::socket> socket_;

to

boost::asio::ssl::stream<boost::asio::ip::tcp::socket> *mpSocket_;

并重构所有与->相关的内容。

但这会导致像这样的错误：

/usr/include/boost/asio/impl/read.hpp:271: error: request for member 'async_read_some' in '((boost::asio::detail::read_op<boost::asio::ssl::stream<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >*, boost::asio::mutable_buffers_1, boost::asio::detail::transfer_all_t, boost::_bi::bind_t<void, boost::_mfi::mf2<void, SSLHandler, const boost::system::error_code&, long unsigned int>, boost::_bi::list3<boost::_bi::value<SSLHandler*>, boost::arg<1> (*)(), boost::arg<2> (*)()> > >*)this)->boost::asio::detail::read_op<boost::asio::ssl::stream<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >*, boost::asio::mutable_buffers_1, boost::asio::detail::transfer_all_t, boost::_bi::bind_t<void, boost::_mfi::mf2<void, SSLHandler, const boost::system::error_code&, long unsigned int>, boost::_bi::list3<boost::_bi::value<SSLHandler*>, boost::arg<1> (*)(), boost::arg<2> (*)()> > >::stream_', which is of pointer type 'boost::asio::ssl::stream<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >*' (maybe you meant to use '->' ?)
          stream_.async_read_some(
          ^

/usr/include/boost/asio/impl/write.hpp:258: error: request for member 'async_write_some' in '((boost::asio::detail::write_op<boost::asio::ssl::stream<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >*, boost::asio::mutable_buffers_1, boost::asio::detail::transfer_all_t, boost::_bi::bind_t<void, boost::_mfi::mf2<void, SSLHandler, const boost::system::error_code&, long unsigned int>, boost::_bi::list3<boost::_bi::value<SSLHandler*>, boost::arg<1> (*)(), boost::arg<2> (*)()> > >*)this)->boost::asio::detail::write_op<boost::asio::ssl::stream<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >*, boost::asio::mutable_buffers_1, boost::asio::detail::transfer_all_t, boost::_bi::bind_t<void, boost::_mfi::mf2<void, SSLHandler, const boost::system::error_code&, long unsigned int>, boost::_bi::list3<boost::_bi::value<SSLHandler*>, boost::arg<1> (*)(), boost::arg<2> (*)()> > >::stream_', which is of pointer type 'boost::asio::ssl::stream<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >*' (maybe you meant to use '->' ?)
          stream_.async_write_some(
          ^

接着我试图取消引用指针以保留旧结构，但是出现了新错误 :(

boost::asio::async_connect(*socket_.lowest_layer(), mEndpointIterator, boost::bind(&SSLHandler::handle_connect, this, boost::asio::placeholders::error));
error: request for member 'lowest_layer' in '((SSLHandler*)this)->SSLHandler::socket_', which is of pointer type 'boost::asio::ssl::stream<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >*' (maybe you meant to use '->' ?)
     boost::asio::async_connect(*socket_.lowest_layer(), mEndpointIterator, boost::bind(&SSLHandler::handle_connect, this, boost::asio::placeholders::error));`

请帮忙，我来自Java，所以这个东西对我来说很复杂。

2
看到你的实际代码会有所帮助。关于你的第二个编译错误：*socket_.lowest_layer() 应该是 (*socket_).lowest_layer()。 - user9408921
请贴出代码中出现错误的部分 / 创建一个 MCVE。 - Blacktempel
“并重构与->相关的所有内容” - 显然你没有正确地做到这一点。你为什么需要使用指针呢？这本来就是一个X/Y问题。 - sehe
感谢关注。很抱歉我错过了一个socket没有改成*socket。 @sehe：请阅读这个。一旦你关闭了socket，就无法重新打开它:( - Patton
@Patton 即使那个回答也承认没有必要使用原始指针。 - sehe
1个回答
6

这是对Boost 1.66.0中示例的最小更改。您可以在github上单独查看我们的补丁：https://github.com/boostorg/asio/compare/develop...sehe:so-q49122521

注意：我将地址解析移动到连接序列中，因为如果网络配置已更改，则结果可能不同，或者应优先选择其他端点之一。

为此，我们存储一个resolver :: query query_ 成员，以便我们可以在重新连接时重复查询。

//
// client.cpp
// ~~~~~~~~~~
//
// Copyright (c) 2003-2018 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 <cstdlib>
#include <iostream>
#include <boost/bind.hpp>
#include <boost/asio.hpp>
#include <boost/asio/ssl.hpp>

enum { max_length = 1024 };

class client
{
public:
  client(boost::asio::io_context& io_context,
      boost::asio::ssl::context& context,
      boost::asio::ip::tcp::resolver::query query)
    : socket_(io_context, context), query_(query), timer_(io_context)
  {
    socket_.set_verify_mode(boost::asio::ssl::verify_peer);
    socket_.set_verify_callback(
        boost::bind(&client::verify_certificate, this, _1, _2));

    start_connect();
  }

  void start_connect() {
    boost::asio::ip::tcp::resolver r(socket_.get_io_context());

    boost::asio::async_connect(socket_.lowest_layer(), r.resolve(query_),
        boost::bind(&client::handle_connect, this,
          boost::asio::placeholders::error));
  }

  void do_reconnect() {
    timer_.expires_from_now(boost::posix_time::millisec(500));
    timer_.async_wait(boost::bind(&client::handle_reconnect_timer, this, boost::asio::placeholders::error));
  }

  void handle_reconnect_timer(boost::system::error_code ec) {
    if (!ec) {
      start_connect();
    }
  }

  bool verify_certificate(bool preverified,
      boost::asio::ssl::verify_context& ctx)
  {
    // The verify callback can be used to check whether the certificate that is
    // being presented is valid for the peer. For example, RFC 2818 describes
    // the steps involved in doing this for HTTPS. Consult the OpenSSL
    // documentation for more details. Note that the callback is called once
    // for each certificate in the certificate chain, starting from the root
    // certificate authority.

    // In this example we will simply print the certificate's subject name.
    char subject_name[256];
    X509* cert = X509_STORE_CTX_get_current_cert(ctx.native_handle());
    X509_NAME_oneline(X509_get_subject_name(cert), subject_name, 256);
    std::cout << "Verifying " << subject_name << "\n";

    return preverified;
  }

  void handle_connect(const boost::system::error_code& error)
  {
    if (!error)
    {
      socket_.async_handshake(boost::asio::ssl::stream_base::client,
          boost::bind(&client::handle_handshake, this,
            boost::asio::placeholders::error));
    }
    else
    {
      std::cout << "Connect failed: " << error.message() << "\n";
      do_reconnect();
    }
  }

  void accept_message() {
      std::cout << "Enter message: ";
      std::cin.getline(request_, max_length);
      size_t request_length = strlen(request_);

      boost::asio::async_write(socket_,
          boost::asio::buffer(request_, request_length),
          boost::bind(&client::handle_write, this,
            boost::asio::placeholders::error,
            boost::asio::placeholders::bytes_transferred));
    }

  void handle_handshake(const boost::system::error_code& error)
  {
    if (!error)
    {
      accept_message();
    }
    else
    {
      std::cout << "Handshake failed: " << error.message() << "\n";
      do_reconnect();
    }
  }

  void handle_write(const boost::system::error_code& error,
      size_t bytes_transferred)
  {
    if (!error)
    {
      boost::asio::async_read(socket_,
          boost::asio::buffer(reply_, bytes_transferred),
          boost::bind(&client::handle_read, this,
            boost::asio::placeholders::error,
            boost::asio::placeholders::bytes_transferred));
    }
    else
    {
      std::cout << "Write failed: " << error.message() << "\n";
      do_reconnect();
    }
  }

  void handle_read(const boost::system::error_code& error,
      size_t bytes_transferred)
  {
    if (!error)
    {
      std::cout << "Reply: ";
      std::cout.write(reply_, bytes_transferred);
      std::cout << "\n";

      accept_message(); // continue using the same socket_ until fail
    }
    else
    {
      std::cout << "Read failed: " << error.message() << "\n";
      do_reconnect();
    }
  }

private:
  boost::asio::ssl::stream<boost::asio::ip::tcp::socket> socket_;
  boost::asio::ip::tcp::resolver::query query_;
  boost::asio::deadline_timer timer_;
  char request_[max_length];
  char reply_[max_length];
};

int main(int argc, char* argv[])
{
  try
  {
    if (argc != 3)
    {
      std::cerr << "Usage: client <host> <port>\n";
      return 1;
    }

    boost::asio::io_context io_context;
    boost::asio::ssl::context ctx(boost::asio::ssl::context::sslv23);
    ctx.load_verify_file("ca.pem");

        client c(io_context, ctx, {argv[1], argv[2]});

    io_context.run();
  }
  catch (std::exception& e)
  {
    std::cerr << "Exception: " << e.what() << "\n";
  }

  return 0;
}

这是实时演示：

输入图像描述

进一步思考

根据您的偏执程度，您可能会更愿意在 do_reconnect() 中实际关闭ssl流：

boost::system::error_code ec;
socket_.shutdown(ec);
if (ec) std::cout << "shutdown error: " << ec.message() << std::endl;

那也可以。你甚至可以决定杀死任何最低级别的连接，以防万一：
auto& ll = socket_.lowest_layer();

if (ll.is_open())
{
  ll.shutdown(boost::asio::ip::tcp::socket::shutdown_both, ec);
  //if (ec) std::cout << "socket.shutdown error: " << ec.message() << std::endl;

  ll.close(ec);
  //if (ec) std::cout << "socket.close error: " << ec.message() << std::endl;
}

使用动态分配的套接字

正如先前提到的那样，最纯粹的解决方案是不重用流/套接字对象：

boost::optional<stream> socket_;

现在，更新所有间接引用socket_的参考，do_reconnect() 可以变成：

void do_reconnect() {
  auto& io_context = socket_->get_io_context();
  {
      boost::system::error_code ec;
      socket_->shutdown(ec);
      if (ec) std::cout << "shutdown error: " << ec.message() << std::endl;
  }

  socket_.emplace(io_context, context_);

  timer_.expires_from_now(boost::posix_time::millisec(500));
  timer_.async_wait(boost::bind(&client::handle_reconnect_timer, this, boost::asio::placeholders::error));
}

当然这也可以正常工作。
以下是相应的补丁：https://github.com/boostorg/asio/compare/develop...sehe:so-q49122521-dynamic。
//
// client.cpp
// ~~~~~~~~~~
//
// Copyright (c) 2003-2018 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 <cstdlib>
#include <iostream>
#include <boost/optional.hpp>
#include <boost/bind.hpp>
#include <boost/asio.hpp>
#include <boost/asio/ssl.hpp>

enum { max_length = 1024 };

namespace ssl = boost::asio::ssl;
using tcp = boost::asio::ip::tcp;

class client
{
    using stream = ssl::stream<tcp::socket>;
public:
  client(boost::asio::io_context& io_context, ssl::context& context, tcp::resolver::query query)
    : context_(context), socket_(boost::in_place_init, io_context, context_), query_(query), timer_(io_context)
  {
    socket_->set_verify_mode(ssl::verify_peer);
    socket_->set_verify_callback(
        boost::bind(&client::verify_certificate, this, _1, _2));

    start_connect();
  }

  void start_connect() {
    tcp::resolver r(socket_->get_io_context());

    boost::asio::async_connect(socket_->lowest_layer(), r.resolve(query_),
        boost::bind(&client::handle_connect, this,
          boost::asio::placeholders::error));
  }

  void do_reconnect() {
    auto& io_context = socket_->get_io_context();
    {
        boost::system::error_code ec;
        socket_->shutdown(ec);
        if (ec) std::cout << "shutdown error: " << ec.message() << std::endl;
    }

    socket_.emplace(io_context, context_);

    timer_.expires_from_now(boost::posix_time::millisec(500));
    timer_.async_wait(boost::bind(&client::handle_reconnect_timer, this, boost::asio::placeholders::error));
  }

  void handle_reconnect_timer(boost::system::error_code ec) {
    if (!ec) {
      start_connect();
    }
  }

  bool verify_certificate(bool preverified,
      ssl::verify_context& ctx)
  {
    // The verify callback can be used to check whether the certificate that is
    // being presented is valid for the peer. For example, RFC 2818 describes
    // the steps involved in doing this for HTTPS. Consult the OpenSSL
    // documentation for more details. Note that the callback is called once
    // for each certificate in the certificate chain, starting from the root
    // certificate authority.

    // In this example we will simply print the certificate's subject name.
    char subject_name[256];
    X509* cert = X509_STORE_CTX_get_current_cert(ctx.native_handle());
    X509_NAME_oneline(X509_get_subject_name(cert), subject_name, 256);
    std::cout << "Verifying " << subject_name << "\n";

    return preverified;
  }

  void handle_connect(const boost::system::error_code& error)
  {
    if (!error)
    {
      socket_->async_handshake(ssl::stream_base::client,
          boost::bind(&client::handle_handshake, this,
            boost::asio::placeholders::error));
    }
    else
    {
      std::cout << "Connect failed: " << error.message() << "\n";
      do_reconnect();
    }
  }

  void accept_message() {
    std::cout << "Enter message: ";
    std::cin.getline(request_, max_length);
    size_t request_length = strlen(request_);

    boost::asio::async_write(*socket_,
        boost::asio::buffer(request_, request_length),
        boost::bind(&client::handle_write, this,
          boost::asio::placeholders::error,
          boost::asio::placeholders::bytes_transferred));
  }

  void handle_handshake(const boost::system::error_code& error)
  {
    if (!error)
    {
      accept_message();
    }
    else
    {
      std::cout << "Handshake failed: " << error.message() << "\n";
      do_reconnect();
    }
  }

  void handle_write(const boost::system::error_code& error,
      size_t bytes_transferred)
  {
    if (!error)
    {
      boost::asio::async_read(*socket_,
          boost::asio::buffer(reply_, bytes_transferred),
          boost::bind(&client::handle_read, this,
            boost::asio::placeholders::error,
            boost::asio::placeholders::bytes_transferred));
    }
    else
    {
      std::cout << "Write failed: " << error.message() << "\n";
      do_reconnect();
    }
  }

  void handle_read(const boost::system::error_code& error,
      size_t bytes_transferred)
  {
    if (!error)
    {
      std::cout << "Reply: ";
      std::cout.write(reply_, bytes_transferred);
      std::cout << "\n";

      accept_message(); // continue using the same socket_ until fail
    }
    else
    {
      std::cout << "Read failed: " << error.message() << "\n";
      do_reconnect();
    }
  }

private:
  ssl::context& context_;

  boost::optional<stream> socket_;
  tcp::resolver::query query_;
  boost::asio::deadline_timer timer_;
  char request_[max_length];
  char reply_[max_length];
};

int main(int argc, char* argv[])
{
    try
    {
        if (argc != 3)
        {
            std::cerr << "Usage: client <host> <port>\n";
            return 1;
        }

        boost::asio::io_context io_context;
        ssl::context ctx(ssl::context::sslv23);
        ctx.load_verify_file("ca.pem");

        client c(io_context, ctx, {argv[1], argv[2]});

        io_context.run();
    }
    catch (std::exception& e)
    {
        std::cerr << "Exception: " << e.what() << "\n";
    }

    return 0;
}
首先，非常感谢您提供的详细答案，对我来说意义重大。但是您使用的是哪个版本的boost呢？我使用的是1.56版本，boost::asio::ssl::stream<boost::asio::ip::tcp::socket> socket_;没有get_io_context()方法。 - Patton
嗨，我遇到了麻烦，调用boost::system::error_code ec; socket_->shutdown(ec); if (ec) std::cout << "shutdown error: " << ec.message() << std::endl;后，服务器和客户端仍然可以发送和接收消息。 - Patton
关闭客户端中的 SSL 如何阻止服务器或其他客户端呢？ - sehe
如果您只想在每个消息后无条件地获得新连接，只需实例化新的“client”实例即可。 - sehe
我忘了提到这是额外的问题：当从上层接收到断开命令时，我想要断开套接字。关闭函数没有终止套接字。 - Patton
显示剩余10条评论
网页内容由stack overflow 提供, 点击上面的
可以查看英文原文，
原文链接