* Transfer rate is better than BTLE, no comment in Apple document said there is package limit in transformation, some message said it has a limitation of 87K, in real device test(ip4-Air), it can transfer 500K/package, but the transfer speed and UE is not good, 100-200K is suggested.
* Sending data seem won't block the current thread, or it has a buffer to store the data.
* If not care the package order and stability, GKSendDataUnreliable will more efficient.
* Can use to send files 3-5M in practice.