Hi I have come across the example for serialization in http://www.boost.org/doc/libs/1_43_0/doc/html/boost_asio/example/serializati... In the following method async_write, the data typename T is put into an archive before being sent out. I would need to do the same thing here but the archive should be binary stream because I need to send this data to a third party application which expects a binary stream. Does anyone know how to do it? Thanks & Regards Long /// Asynchronously write a data structure to the socket. template <typename T, typename Handler> void async_write(const T& t, Handler handler) { // Serialize the data first so we know how large it is. std::ostringstream archive_stream; boost::archive::text_oarchive archive(archive_stream); archive << t; outbound_data_ = archive_stream.str(); // Format the header. std::ostringstream header_stream; header_stream << std::setw(header_length) << std::hex << outbound_data_.size(); if (!header_stream || header_stream.str().size() != header_length) { // Something went wrong, inform the caller. boost::system::error_code error(boost::asio::error::invalid_argument); socket_.io_service().post(boost::bind(handler, error)); return; } outbound_header_ = header_stream.str(); // Write the serialized data to the socket. We use "gather-write" to send // both the header and the data in a single write operation. std::vector<boost::asio::const_buffer> buffers; buffers.push_back(boost::asio::buffer(outbound_header_)); buffers.push_back(boost::asio::buffer(outbound_data_)); boost::asio::async_write(socket_, buffers, handler); } _________________________________________________________________