an echo server base on boost asio.
It's just a demo show how to use boost asio.
1、use boost::spawn to create coroutines .
2、passed lamda to the coroutine handles.
3、show how coroutines worked
4、show how std::enable_shared_from_this and shared_from_this used
5、test the case without coroutine ，use default lamda callback
6、show the basic asio method and structure in the demo ，ip::tcp::endpoint， ip::tcp::socket， async_accept， async_receive， async_send asio::buffer etc.
Use boost::spawn to create stackfull coroutines
boost 1.64