- no need to do server discovery, manual enter it on client startup
- let server be a idiot, just use client provided 
information to do task and decide what to do
- let client keep their status, and send what should lobby server do for them
- lobby should keep each users state and ip, port, for sending msg
- client should do all the jobs flow
- server is just act like a tool for client, not a controler
- read write to sql table function share a lock(just 1 for 2 table) for prevent race condition

Q : 
    how client let user choice what do do, and simutanously listen for invitation
    A: use select do asycnronize console input and socket input
========  server  =========================================================
(A) - open_lobby()  : enter port info, open a socket and listen, print server's ip,port info
- create user table, game table and connect to mysql 
(B) - user_exist_check
    - user_register(act,username,hash_passwd)-->{success?, msg}
        check if user exist?
(C) - check user status and exist?
    - match password
        if match:
            update status(also check if last is not log out, send notify to old ipport for serve logout) 
            generate token
            store client connect info(ip, port)
            after client ack, update table and status
(D) - logout(token)
        remove online state and connect information
        remove room create by the client
(E) - display_user():
        no need to check user's token
        sql select user not offline
    - display_room():
        sql select room is public and their status
(F) - create_room():
        check if the user is idle and login
        room_type: public, private
        roome info,p1 p2
    - invite_peer():
        check p2's login status
        send peer invite to p2, wait respond(with timeout 15s)
        update user_status
        notify invite status to p1(accept, reject, timeout, failed?)
        [if success] ask p1 game room's ip port
        send game room conn info to p2
        [if failed]
            update user status
    - notify_game_start(p1,p2 roomid):
        update p1,p2 status and game room status
(H) - add to public():
        check p2 status
        update game table, user table



==========  client  =============================
msg_sender(json)-->status code, received data
    handle connection error, send and receive request <--> game lobby
user_reg():
    ask user to set name and passwd, hash it and sent to server
    use the return status code to print msg or ask user to provie info again
login():
    ask username, check exist?
    ask passwd, hash it and send to server(name,hashed_passwd)
    handle server response
    store token
    bring to in_menu
    display_user
    display_room
logout():
    send token to server
    clear global var token
    kick user to out_menu
display_user(), display_room() :
    check if user is login, and is at lobby
    trigger by user login success
create_room():
    check login status
    ask room type
    ask game type
    send room create to server
    list user
    ask invite
join_public room():
    send join to server
    wait serve response
    create game server
    send game server's conn info to lobby
game_server1()
game_client1()
game_server2()
game_client2()



in_menu:
    create room(room type? game type?)
    join public room?
    wait invitation(control-C to break and return to in_menu)
    list room
    list user
    logout
out_menu:
    client exit
    login