I have excellent experience working with PJSIP library, XMPP based chat clients, configuring Openfire server, Smack library, working with XMPP protocols, developing VoIP clients and solutions working with SIP clients and much more.
I am an expert in developing WebSocket, webRTC, based messaging application. I can also develop and setup the backend completely with custom APIs and setting up the open fire or ejabbered server.