1

我在 Windows 上使用 Boost::ASIO 版本 1.52.0 和 SSL 版本 C，在运行 Win 8 的测试机器上使用 VC++ 中的 Visual Studio 2008 代码。

我有一些代码可以成功连接到具有给定 URL 的 TCP 服务器：

// Create the resolver and query objects to resolve the host name in serverPath to an ip address.
boost::asio::ip::tcp::resolver resolver(*IOService);
boost::asio::ip::tcp::resolver::query query(serverPath, port);
boost::asio::ip::tcp::resolver::iterator EndpointIterator = resolver.resolve(query);
// Set up an SSL context.
boost::asio::ssl::context ctx(*IOService, boost::asio::ssl::context::tlsv1_client);
// Specify to not verify the server certificiate right now.
ctx.set_verify_mode(boost::asio::ssl::context::verify_none);
// Init the socket object used to initially communicate with the server.
pSocket = new boost::asio::ssl::stream<boost::asio::ip::tcp::socket>(*IOService, ctx);
//
// The thread we are on now, is most likely the user interface thread.  Create a thread to handle all incoming socket work messages.
// This thread is created for each connection to a server.
if (!RcvThreadCreated)
{
   WorkerThreads.create_thread(boost::bind(&SSLSocket::RcvWorkerThread, this));
   RcvThreadCreated = true;
   WorkerThreads.create_thread(boost::bind(&SSLSocket::SendWorkerThread, this));
}
// Try to connect to the server.  Note - add timeout logic at some point.
boost::asio::async_connect(pSocket->lowest_layer(), EndpointIterator,
   boost::bind(&SSLSocket::HandleConnect, this, boost::asio::placeholders::error));

根据一些研究，如果将 IP 地址替换为 serverPath 中的 URL，则无法使用上述解析 IP 地址的代码。看起来正确的方法是创建这样的端点：

const boost::asio::ip::address IP(boost::asio::ip::address::from_string(serverPath));
int iport = atoi(port.c_str());
boost::asio::ip::tcp::endpoint EP(IP, iport);

这部分似乎可以编译。但是，稍后在 async_connect 方法中：

// Try to connect to the server.  Note - add timeout logic at some point.
boost::asio::async_connect(pSocket->lowest_layer(), EP,
boost::bind(&SSLSocket::HandleConnect, this, boost::asio::placeholders::error));

它会产生错误。我猜 async_connect 方法希望看到第二个参数的迭代器。但是，我不确定如何创建一个。

根据以下链接，答案表明可以使用套接字对象上的连接方法。但是，当我尝试这样做时：

pSocket->connect(EP);

编译器给出错误 - 错误 C2039：

'connect' : is not a member of 'boost::asio::ssl::stream<Stream>'

那么，有人可以展示一些简单的代码，提供一种使用 IP 地址而不是 URL 连接到服务器的方法吗？

如果这不可能，那么有没有办法从 IP 地址进行反向查找以获取 URL？

4

2 回答 2

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您的 async_connect() 代码行未编译，因为您正在传递成员函数指针而没有将实例绑定到它。您已经在代码的其他位置正确绑定了成员函数，所以我认为这只是一个疏忽。正确的行是这样的：

pSocket->next_layer().async_connect(
    EP,
    boost::bind(&SSLSocket::HandleConnect, this, boost::asio::placeholder::error));

至于您的原始问题，获取 IP 地址的端点，在 IP 地址查询上使用 ip::tcp::resolver 工作正常，因此您不必为名称和地址设置单独的代码路径。在 ssl::stream 上使用最低层() 来访问底层 ip::tcp::socket 是访问 connect() 和 async_connect() 的正确方法。

除了使用 ssl::context 创建 ssl::stream 并在建立连接后使用 async_handshake() 之外，您的 SSL 代码应该与您的 TCP 代码几乎相同。您也可以在 TCP 代码中使用最低层（）（它只是返回自身），这可以强调相似之处。

我不保证此代码可以编译，因为我从工作代码中对其进行了简化，但是如果您执行 async_resolve()，您的解析处理程序方法将类似于（sp_是套接字/流指针）：

void Pimpl::handleResolve(
  const boost::system::error_code& ec,
  boost::asio::ip::tcp::resolver::iterator endpointIterator) {
  if (ec) {
    // error handling here
    return;      
  }
  sp_->lowest_layer().async_connect( 
     *endpointIterator,
     boost::bind(&Pimpl::handleConnect, this, endpointIterator, boost::asio::placeholder::error));
}

然后您的连接处理程序将看起来像（这会尝试端点，直到它得到一个可以工作或不再有的端点）：

void Pimpl::handleConnect(
  boost::asio::ip::tcp::resolver::iterator endpointIterator,
  const boost::system::error_code& ec) {
  if (!ec) {
    sp_->async_handshake(
      boost::asio::ssl::stream_base::client,
      boost::bind(&Pimpl::handleHandshake, this, boost::asio::placeholder::error));
  }
  else if (++endpointIterator != boost::asio::ip::tcp::resolver::iterator()) {
    // Try connecting to the next endpoint.
    sp_->lowest_layer().close();
    sp_->lowest_layer().async_connect(
      *endpointIterator,
      boost::bind(&Pimpl::handleConnect, this, endpointIterator, boost::asio::placeholder::error));
  }
  else {
    // error handling here
  }
}

唯一使它特定于 ssl::stream 指针而不是 ip::tcp::socket 指针的行是 async_handshake() 调用。

于 2013-02-28T23:52:10.207 回答
0

我找到了解决这个问题的方法。我正在使用 ssl::stream 类作为套接字对象，错误的原因是因为它没有连接方法。但是，它确实有一个 next_layer() 方法，该方法返回一个可以调用 connect 或 async_connect 方法的对象。我在编译 async_connect 时遇到问题，但 connect 方法有效。然后我像这样调用我的 HandleConnect 方法：

boost::system::error_code EC;
pSocket->next_layer().connect(EP, EC);
HandleConnect(EC);

为了回答@SamMiller 对代码的请求，它在下面给出。我仍然想知道如何为 boost::asio::async_connect 调用的端点创建一个迭代器，以及如何调用 next_layer 对象的 async_connect 方法。

void SSLSocket::Connect(SSLSocket* psSLS, const string& serverPath, string& port)
{
   // Connects to the server.
   // serverPath - specifies the path to the server.  Can be either an ip address or url.
   // port - port server is listening on.
   //
   try
   {
      Locking CodeLock(SocketLock); // Single thread the code.
      // If the user has tried to connect before, then make sure everything is clean before trying to do so again.
      if (pSocket)
      {
         delete pSocket;
         pSocket = 0;
      }                                                                                                  
      // If serverPath is a URL, then resolve the address.
      if ((serverPath[0] < '0') || (serverPath[0] > '9')) // Assumes that the first char of the server path is not a number when resolving to an ip addr.
      {
         // Create the resolver and query objects to resolve the host name in serverPath to an ip address.
         boost::asio::ip::tcp::resolver resolver(*IOService);
         boost::asio::ip::tcp::resolver::query query(serverPath, port);
         boost::asio::ip::tcp::resolver::iterator EndpointIterator = resolver.resolve(query);
         // Set up an SSL context.
         boost::asio::ssl::context ctx(*IOService, boost::asio::ssl::context::tlsv1_client);
         // Specify to not verify the server certificiate right now.
         ctx.set_verify_mode(boost::asio::ssl::context::verify_none);
         // Init the socket object used to initially communicate with the server.
         pSocket = new boost::asio::ssl::stream<boost::asio::ip::tcp::socket>(*IOService, ctx);
         //
         // The thread we are on now, is most likely the user interface thread.  Create a thread to handle all incoming socket work messages.
         // This thread is created for each connection to a server.
         if (!RcvThreadCreated)
         {
            WorkerThreads.create_thread(boost::bind(&SSLSocket::RcvWorkerThread, this));
            RcvThreadCreated = true;
            WorkerThreads.create_thread(boost::bind(&SSLSocket::SendWorkerThread, this));
         }
         // Try to connect to the server.  Note - add timeout logic at some point.
         boost::asio::async_connect(pSocket->lowest_layer(), EndpointIterator,
            boost::bind(&SSLSocket::HandleConnect, this, boost::asio::placeholders::error));
      }
      else
      {
         // serverPath is an ip address, so try to connect using that.
         //
         // Create an endpoint with the specified ip address.
         const boost::asio::ip::address IP(boost::asio::ip::address::from_string(serverPath));
         int iport = atoi(port.c_str());
         const boost::asio::ip::tcp::endpoint EP(IP, iport);
         // Set up an SSL context.
         boost::asio::ssl::context ctx(*IOService, boost::asio::ssl::context::tlsv1_client);
         // Specify to not verify the server certificiate right now.
         ctx.set_verify_mode(boost::asio::ssl::context::verify_none);
         // Init the socket object used to initially communicate with the server.
         pSocket = new boost::asio::ssl::stream<boost::asio::ip::tcp::socket>(*IOService, ctx);
         //
         // The thread we are on now, is most likely the user interface thread.  Create a thread to handle all incoming socket work messages.
         // This thread is created for each connection to a server.
         if (!RcvThreadCreated)
         {
            WorkerThreads.create_thread(boost::bind(&SSLSocket::RcvWorkerThread, this));
            RcvThreadCreated = true;
            WorkerThreads.create_thread(boost::bind(&SSLSocket::SendWorkerThread, this));
         }
         // Try to connect to the server.  Note - add timeout logic at some point.
         // pSocket->next_layer().async_connect(EP, &SSLSocket::HandleConnect);
         boost::system::error_code EC;
         pSocket->next_layer().connect(EP, EC);
         if (EC)
         {
            // Log an error.  This worker thread should exit gracefully after this.
            stringstream ss;
            ss << "SSLSocket::Connect: connect failed to " << sClientIp << " : " << uiClientPort << ".  Error: " << EC.message() + ".\n";
            Log.LogString(ss.str(), LogError);
         }
         HandleConnect(EC);
      }
   }
   catch (std::exception& e)
   {
      stringstream ss;
      ss << "SSLSocket::Connect: threw an error - " << e.what() << ".\n";
      Log.LogString(ss.str(), LogError);
      Stop();
   }
}

这是以下行时生成的错误：

pSocket->next_layer().async_connect(EP, &SSLSocket::HandleConnect); // Does not compile

替换为：

boost::system::error_code EC;
pSocket->next_layer().connect(EP, EC); // Compiles and works properly.

错误信息：

1>c:\boost_1_52_0\boost\asio\basic_socket.hpp(706) : error C2064: term does not evaluate to a function taking 1 arguments
1>        c:\users\bob\documents\visual studio 2008\projects\attackpoker1\win32client\sslsockets\sslsocket.cpp(114) : see reference to function template instantiation 'void boost::asio::basic_socket<Protocol,SocketService>::async_connect<void(__thiscall SSLSocket::* )(const boost::system::error_code &)>(const boost::asio::ip::basic_endpoint<InternetProtocol> &,const ConnectHandler &)' being compiled
1>        with
1>        [
1>            Protocol=boost::asio::ip::tcp,
1>            SocketService=boost::asio::stream_socket_service<boost::asio::ip::tcp>,
1>            InternetProtocol=boost::asio::ip::tcp,
1>            ConnectHandler=void (__thiscall SSLSocket::* )(const boost::system::error_code &)
1>        ]
于 2013-02-22T18:02:51.807 回答