TLS and Websocket connection is serialized unexpectedly

[redboltz]

Problem

When I test my broker that uses mqtt_cpp, I noticed that accepting process of server_tls, server_ws, and server_tls_ws behaves unexpectedly.

The function do_accept() is called after asynchronous underlying processes (handshake, websocket upgrade, etc) are finished.
If underlying processes are stuck, then the next do_accept() isn't called until timeout(#295 ) happens.

Solution

The next do_accept() should be called in the TCP accept handler.
Then asynchronous underlying processes can run concurrently each sockets.

Required change

Remove std::unique_ptr<socket_t> socket_ member variables. It is avoiding concurrent process.

mqtt_cpp/include/mqtt/server.hpp

Line 359 in 5802d04

std::unique_ptr<socket_t> socket_;

Instead of that, create socket_t object locally each do_accept() call. This is common accepting pattern. It requires std::shared_ptr<socket_t> for the local variable socket.

mqtt_cpp/include/mqtt/server.hpp

Line 311 in 5802d04

acceptor_.value().async_accept(