我研究了现有的例子:
但我仍然无法弄清楚如何使用Boost :: asio API传递Google Protobuf消息。特别是我对以下问题没有清楚的认识:
这是基于来自examples的boost :: asio v.1.39 ssl_client的实现。
class client
{
public:
client(boost::asio::io_service& io_service, boost::asio::ssl::context& context,
boost::asio::ip::tcp::resolver::iterator endpoint_iterator)
: socket_(io_service, context),
request_stream(&b),
raw_output(&request_stream),
coded_output(&raw_output)
{
...
}
void handle_connect(const boost::system::error_code& error,
boost::asio::ip::tcp::resolver::iterator endpoint_iterator)
{
...
}
//Debugging function
void print_buffers_condition(const char *step)
{
std::cout << "\nBuffer conditions after " << step << std::endl;
std::cout << "boost::asio::streambuf\t\tb: " << b.size() << std::endl;
std::cout << "google::protobuf::io::OstreamOutputStream raw_output: " << raw_output.ByteCount() << std::endl;
std::cout << "google::protobuf::io::CodedOutputStream coded_output: " << coded_output.ByteCount() << std::endl;
std::cout << std::endl;
}
//Sending test message after SSL Handshake
void handle_handshake(const boost::system::error_code& error)
{
std::cout << "-----------------------------SENDING-----------------------------" << std::endl;
print_buffers_condition("handle handshake");
if (!error)
{
SearchRequest msg;
msg.set_query("qwerty");
msg.set_code(12345);
std::cout << "Debugged" << std::endl;
msg.PrintDebugString();
//Writing the length of the message before and serializing
print_buffers_condition("before serialising");
coded_output.WriteVarint32(msg.ByteSize());
if (!msg.SerializeToCodedStream(&coded_output))
{
std::cout << "serailizing error" << std::endl;
}
else
{
std::cout << "serializing success" << std::endl;
}
//Sending
buffers_condition("before async write");
boost::asio::async_write(socket_,
b,
boost::bind(&client::handle_write, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred));
buffers_condition("after async write");
}
else
{
std::cout << "Handshake failed: " << error << "\n";
}
}
void handle_write(const boost::system::error_code& error,
size_t bytes_transferred)
{
std::cout << " bytes_trransferred: " << bytes_transferred << std::endl;
if (!error)
{
std::cout << "No error" << std::endl;
...
}
else
{
std::cout << "Write failed: " << error << "\n";
}
}
void handle_read(const boost::system::error_code& error,
size_t bytes_transferred)
{
...
}
private:
boost::asio::ssl::stream<boost::asio::ip::tcp::socket> socket_;
boost::asio::streambuf b;
std::ostream request_stream;
google::protobuf::io::OstreamOutputStream raw_output;
google::protobuf::io::CodedOutputStream coded_output;
};
此代码可操作,因此在创建消息后,我们会进入void handle_write(const boost::system::error_code& error, size_t bytes_transferred)
函数。打印bytes_transferred_
值返回0:服务器(在examples的基础上实现)也没有收到任何内容。
调试函数void print_buffers_condition(const char *step)
的使用暗示在通过一堆不同的缓冲对象传输时丢失消息:
$ ./client 127.0.0.1 5000
-----------------------------SENDING-----------------------------
Buffer conditions after handle handshake
boost::asio::streambuf b: 0
google::protobuf::io::OstreamOutputStream raw_output: 8192
google::protobuf::io::CodedOutputStream coded_output: 0
Debugged:
query: "qwerty"
code: 12345
Buffer conditions after before serialization
boost::asio::streambuf b: 0
google::protobuf::io::OstreamOutputStream raw_output: 8192
google::protobuf::io::CodedOutputStream coded_output: 0
serializing success
Buffer conditions after before async write
boost::asio::streambuf b: 0
google::protobuf::io::OstreamOutputStream raw_output: 8192
google::protobuf::io::CodedOutputStream coded_output: 13
Buffer conditions after after async write
boost::asio::streambuf b: 0
google::protobuf::io::OstreamOutputStream raw_output: 8192
google::protobuf::io::CodedOutputStream coded_output: 13
bytes_trransferred: 0
我不知道如何以适当的方式做到这一点。 操作系统是RHEL 6.4。 谢谢。
答案 0 :(得分:3)
我不熟悉asio,但在我看来,问题在于你没有冲洗缓冲区。数据停留在CodedOutputStream
并且永远不会进入asio。
CodedOutputStream
,这样一旦你写完消息就会销毁它。析构函数将刷新缓冲区。请注意CodedOutputStream
分配起来很便宜,因此将它放在堆栈上没有性能问题(事实上,它可能更好)。
OstreamOutputStream
可以类似地在堆栈上分配,但它会堆分配一个您可能想要重用的缓冲区。如果您选择重用同一个对象,请确保在Flush()
被销毁后调用CodedOutputStream
来刷新缓冲区。
顺便说一下,OstreamOutputStream
并不是特别有效,因为它必须在ostream
已经在做的事情之上做自己的缓冲层。您可能希望序列化为字符串(str = message.SerializeAsString()
或message.SerializeToString(&str)
),然后将其直接写入套接字(如果asio允许),因为它可能会避免冗余副本。