Reading data with boost asio on client - boost

Question

I am learning boost asio and have mistake. I have written simple client ( I can send data from it but when I read data I cant even compile it) I used protocol buffer to serialize data . So file #include "test.pb.h" is probuffer class
My code client :
#include <boost/array.hpp>
#include <boost/asio.hpp>
#include <boost/bind.hpp>
#include <boost/foreach.hpp>
#include <boost/lexical_cast.hpp>
#include <boost/thread/thread.hpp>
#include <cstdlib>
#include <iostream>
#include <string>
#include <thread>
#include "test.pb.h"
using boost::asio::ip::tcp;
int main(int argc, char** argv)
{
try
{
// connect to the server:
boost::asio::io_service io_service;
tcp::resolver resolver(io_service);
std::string const server_address = "localhost";
std::string const server_port = "10000";
tcp::resolver::query query(server_address, server_port);
tcp::resolver::iterator endpoint_iterator = resolver.resolve(query);
tcp::socket socket(io_service);
boost::asio::connect(socket, endpoint_iterator);
//while ( true)
{
Person p = Person();
p.set_id(22);
p.set_name("Jack vorobey");
// std::cout << p.id();
// std::cout << p.name();
std::string data; // this will hold serialized data
bool ok = p.SerializeToString(&data);
assert(ok);
// std::cout << data.size() << std::endl;
boost::asio::write(socket, boost::asio::buffer(data))
boost::asio::read(socket, boost::asio::buffer(data));;
// break; // Connection closed cleanly by peer.
// std::cout << data.size() << std::endl; // shows a reduction in amount of
remaining data
// boost::asio::read(socket, boost::asio::buffer(data) /*,
}
boost::asio::transfer_exactly(65536) */);
}
catch (std::exception& e)
{
//std::cerr << e.what(luuu) << std::endl;
}
std::cout << "\nClosing";
std::string dummy;
}
The code of my mistake I dont understand :
error C2679: binary '=' : no operator found which takes a right-hand operand of type 'const boost::asio::const_buffer' (or there is no acceptable conversion)
1> c:\local\boost_1_55_0\boost\asio\buffer.hpp(136): could be 'boost::asio::mutable_buffer &boost::asio::mutable_buffer::operator =(const boost::asio::mutable_buffer &)'
1> while trying to match the argument list '(boost::asio::mutable_buffer, const boost::asio::const_buffer)'

Answer 1

This is because template<typename Elem, typename Traits, typename Allocator> const_buffers_1 buffer(const std::basic_string<Elem, Traits, Allocator> &) returns an instance of const_buffers_1 (which is a model of ConstBufferSequence concept). Certainly, you cannot read data into a constant buffer.
Do not read data into a std::string, because it's not intended for that (note that its c_str() and data() member functions return const char*). Instead, allocate another buffer or use asio::streambuf.

Answer 2

You can use a streambuf, or specify the (preallocated!) size:
#include <boost/asio.hpp>
#include <string>
using boost::asio::ip::tcp;
int main()
{
boost::asio::io_service io_service;
tcp::resolver resolver(io_service);
tcp::socket socket(io_service);
boost::asio::connect(socket, resolver.resolve(tcp::resolver::query("localhost", "10000")));
std::string request("request");
boost::asio::write(socket, boost::asio::buffer(request));
#if 0
std::string response;
response.resize(32);
boost::asio::read(socket, boost::asio::buffer(&response[0], response.size()));
#else
boost::asio::streambuf response;
boost::asio::read(socket, response);
#endif
}