Linphone - Linphone is an internet phone or Voice Over IP phone (VoIP).
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
MicroSIP - MicroSIP is a free portable SIP softphone for Windows based on PJSIP stack.
Skype - Stay in touch with your family and friends for free on Skype. Download Skype today to chat and call on desktop and mobile.
We-Talk - Free online chat rooms where people chat and meet each other and chat with the stranger and learn new cultures and make friends.
StealthChat - StealthChat is Encrypted, Private, Secure Calls and Chats on Android and Apple iOS