Question

I have a client that sends me data using this function:

void CServerRetrieve::Send(char *buf, DWORD size, int flags)
{
    unsigned char *zlib;
    unsigned long szzlib;
    m_zlib.Deflate((unsigned char*)buf, size + 1, &zlib, &szzlib); // include the terminating 0 char
    char zbuf[5];
    zbuf[0] = 'Z';
    memcpy(&zbuf[1], &szzlib, 4);
    send(m_Socket, zbuf, 5, flags);
    send(m_Socket, (char*)zlib, szzlib, flags);
    delete [] zlib;
}

I want to receive this data using Boost::asio, however I am not sure what type of buffer I should pass to socket.async_receive in order for it to receive this data?

I have tried a std::vector<char> and std::vector<std::string>, however no data is ever received in my buffer?

Can someone assist me as to what I’m doing wrong?

void tcp_connection::start()
{
    socket_.async_receive(boost::asio::buffer(buff), boost::bind(&tcp_connection::handle_read, shared_from_this(), boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred));
}

void tcp_connection::handle_read(const boost::system::error_code& err, size_t bytes_transferred)
{
    if (!err || err ==  boost::asio::error::message_size)
    {
        size_t sz = buff.size(); //always 0!
    }
}

Answer 1

The fact that you are receiving compressed data really does not matter to Boost.Asio. Assuming you you know the size of the data you are about to receive, a std::vector<char> is fine for receiving the compressed data. You’ll need to resize it prior to invoking async_receive Just make sure this buffer does not go out of scope until the completion handler is invoked. This concept is explained int the async_read documentation.

buffers

One or more buffers into which the data will be read. The sum
of the buffer sizes indicates the
maximum number of bytes to read from
the stream. Although the buffers
object may be copied as necessary,
ownership of the underlying memory
blocks is retained by the caller,
which must guarantee that they remain
valid until the handler is called.