Is it possible to do async_handshake after reading from socket prior using Boost::asio?

Question

I have a boost::asio::ssl::stream typed socket. When boost first accepts a connection to this socket, I want to peek at some byt

Answer 1

After investigating the implementation of async_handshake's buffer overload method, it appears that the buffer must already have the handshake read in.

I attempted that but still encountered issues, I kept getting an error code saying that the SSL version was incorrect. I knew this was not the issue because not using the buffered overload of async_handshake worked fine!

The solution was then to also limit the buffer parameter's size.

typedef socket_type boost::asio::ssl::stream;
void OnAccept(std::shared_ptr socket)
{
    const uint bytesToPeek = 4;
    boost::asio::mutable_buffers_1 sslBuffer(m_Buffer.data(), m_Buffer.size());
    // I'm going to read 4 bytes from the socket.
    boost::system::error_code ec;
    std::size_t readBytes = boost::asio::read(socket->next_layer(), boost::asio::buffer(sslBuffer, bytesToPeek), ec);
    if(ec) { Stop(); return; } // pseudo

    // Check the bytes I read in the buffer

    // Read in the rest of the handshake.
    std::size_t bytesOfHandshake = socket->next_layer().read_some(boost::asio::buffer(sslBuffer+bytesToPeek, 4000));
    bytesOfHandshake += bytesToPeek;

    // Finish the handshake.
    socket->async_handshake(boost::asio::ssl::stream_base::server, boost::asio::buffer(sslBuffer, bytesOfHandshake), &handler);
}

Note that both the read and read_some calls in this should also be made async. I just wanted to demonstrate the answer without handlers.