a) event_join and event_leave are server only... no need to IFDEF then.
b) Have you tried 1's and 0's for TRUE and FALSE. These are vars after all, not strings.
c) Once you get everything done, you do realize that that message is being sent to all clients currently logged in. This may be fine since if you are already in for a long time it's ok to start but if you get two poeple coming into your game at the same time, as soon as one is ready, the other will also get the go-ahead whether it's ready or not. Something for you to think about in your network object flow design.