linux下的tcp传输类，支持阻塞模式、非阻塞模式-linux tcp transfer under the category, to support blocking mode, non-blocking mode

Simple echo server based on a listening pp::TCPSocket. This server handles just one connection at a time and will echo back whatever bytes get sent to it. -Simple echo server based on a listening pp::TCPSocket. This server handles just one connec

实现基于EPOLL的tcp服务端、客户端的封装。(EPOLL based implementation of TCP server, client package)