I am looking for a cross platform for the same WiFi messaging app, where can I find one?

[aFoulMouth]

looking for a cross platform same WiFi messaging app

Hi!
I'm looking for a cross platform (android, ios) messaging app --over the same WiFi network--- (no internet access).
features I'd like to see would be voice calls, private chats, group chats, voice messaging, file sharing.
in Summary similar to whatsapp.

searching the play store I've found the following apps:
WiFi Chat by coldbeans
WiTalky- WiFi Chat & Sharing by witalky group
WiFi Chat & File share Groups by smartdroid solutions
Wi-Fi Talkie FREE\ Wi-Fi Talkie by remaller
WiFive - Wi-Fi chat by Dimitry Ivanov
YO! - Chat & Share over WiFi by yo.com
Talk Wifi by Mlc.

a lot of these apps fit my needs but I do not know how to check if they are cross platform (don't own an iphone).
please help me find the best cross platform app.