Mobile friendly web app chat in Java

I am looking for a developer to create a mobile-friendly web app chat using Java. The project will require one-on-one messaging functionality (with ability to invite others to the chat) and should include file sharing capabilities. I have no specific preference for a framework or library, so I am open to suggestions. Additionally, I would like the chat app to support file sharing. Ideal skills and experience for this project include proficiency in Java, experience in developing mobile-friendly web apps, and expertise in chat app functionality. Very aggressive timelines (days).