What PaulS is saying is that you can't just have everybody jabbering at the same time, you must have some control.
the coordinator reads a packet and determines from which end device is from.
But if everyone is talking over each other the packet may be corrupted.
send silence messages to end devices less the one you are insterest to talk and then just talk with him
That is a bit back to front really. Better to have every one quite by default and specifically allow one to talk.
Any form of multi-master (all talking at once) will give you grief, much easier to have master/slave.
Unless there is a very good reason for multi-master then polling is better/easier.
Master: #1, what's your value
#1 : 123
Master: #2, what's your value
#2 : 456
Master: #3, what's your value
#3 : 789