network includes the following modules:

• nw_buf : buf manager
• nw_evt : main loop
• nw_sock : socket releated
• nw_ses : network session manager
• nw_timer : timer, call a function after specify time, repeat or not repeat
• nw_svr : server implement, one server can bind multi address in different sock type
• nw_clt : client implement, auto reconnect
• nw_state : state machine with timeout
• nw_job : thread pool