Now has a business scenario, there is a PC machine, there are 60 tablets, link through a router, PC and router with Ethernet cable connection, tablet wifi connection, I want to send a picture of a 200 k to the 60 terminals, require 1 s to receive at the same time, this kind of business, I initially using netty as communication framework, use TCP to send, when I send to 20 terminals, probably time around 1-2 s, the increasing number of terminal, found serious delay, this time what to do, if use multicast, there may be lost package, that how to fill the bag, hope to get your advice on
If there is a great god has been implemented, or practice, can talk about cooperation, to give a certain reward

Ps: the actual scenario is to be encountered in the screen sharing, my train of thought is when switching the screen screenshots and send automatically,