Android, iOS and Web. developer needy .

Requirements 1. We need a Server push that can support Android, iOS and Web. 2. User can communicate with word or picture by this system, like WhatsApp or Facebook chat 3. Reference : [login to view URL] User story : 1. Register a new account only need user name and password. 2. When users log in the system by Android, iOS or Web, they can see their friend groups in a list ;. 3. Users can choose one or several friends, and make a chat. 4. Users can watch their chat history in the chat window. We need a functional-orientation back-end, emphasizing on Server and Database. It doesn't matter how it performs on such UI layout.