Serializing binary data in boost fails with `invalid signature' error

Question

I'm having difficulties figuring out correct way of using boost serialization/asio to send objects over network. The message class is as simple as possible. It's not C++ friendly nor suitable for my needs, I just keep it simple temporarily to test asio/ser:

class message {
    friend class boost::serialization::access;
public:
    message(){}
    int type;
    int sender;
    int assignment;
    int nogood;

    template<class Archive>
    void serialize(Archive & ar, const unsigned int version)
    {
        ar & type;
        ar & sender;
        ar & assignment;
        ar & nogood;
    }
};

On the client side when agent decides to send a message, sends it to server over it's tcp connection:

message m;
// do something to generate message
boost::asio::streambuf bufx;
std::ostream os( &bufx );
boost::archive::binary_oarchive ar( os );
ar & m;
boost::asio::write( socket, bufx);

Server side code:

boost::asio::streambuf bufx;
std::istream is(&bufx);
boost::archive::binary_iarchive ia(is);  // <--- Exception: invalid signature
size_t rcx = asio::read(socket,bufx);
message m;
ia >> m;

heon · Accepted Answer · 2014-04-11 06:10:42Z

I got same exception.

And This official example helps me.

If you are still in trouble, try this.

size_t n = sock.receive(bufs);

// received data is "committed" from output sequence to input sequence
b.commit(n);

std::istream is(&b);
std::string s;
is >> s;

In my case, I use async_read. Actually, I modified the example.

  boost::asio::streambuf inbound_;
  boost::asio::streambuf::mutable_buffers_type bufs = inbound_.prepare(inbound_data_size);
  void (connection::*f)(
      const boost::system::error_code&, std::size_t,
      T&, boost::tuple<Handler>)
    = &connection::handle_read_data<T, Handler>;
  boost::asio::async_read(socket_, boost::asio::buffer(bufs), 
    boost::bind(f, this,
      boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred, boost::ref(t), handler));

And then at the handler

  /// Handle a completed read of message data.
  template <typename T, typename Handler>
  void handle_read_data(const boost::system::error_code& e, std::size_t bytes_transferred,
      T& t, boost::tuple<Handler> handler)
  {
    if (e)
    {
      boost::get<0>(handler)(e);
    }
    else
    {
      // Extract the data structure from the data just received.
      try
      {
        inbound_.commit(bytes_transferred);
        std::istream archive_stream(&inbound_);
        boost::archive::binary_iarchive archive(archive_stream);
        archive >> t;
      }
      catch (std::exception& err)
      {
        // Unable to decode data.
        boost::system::error_code error(boost::asio::error::invalid_argument);
        boost::get<0>(handler)(error);
        return;
      }

      // Inform caller that data has been received ok.
      boost::get<0>(handler)(e);
    }
  }

rhashimoto · Accepted Answer · 2013-05-18 14:10:55Z

1

In your server-side code, your streambuf is empty when you create the binary archive. If the archive constructor is looking for a magic number at the beginning of the archive then it won't find it. Try filling the streambuf with the call to boost::asio::read() before constructing the stream and archive.

answered May 18, 2013 at 14:10

rhashimoto

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2 Comments

Soroush Rabiei Over a year ago

Tanks for your answer. I moved read() immediately after streambuf definition. Now read throws an exception with this message: End of file

rhashimoto Over a year ago

I believe that is expected. read() blocks until the buffer is full or an error occurs. In this case the "error" is that the socket has closed. You may wish to use the read() overload that returns status via a boost::system::error_code reference argument instead of throwing on error.

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