Integrating web sockets and XMPP issues in nodejs

I am building multi-user, multi-seller e-commerece website in which i used websockets for now and only build realtime events for now and messages are gone towards both sides on realtime. But my question is that if specific user can start the conversation, it emits the event and before sending to to seller dashboard, it is necessary to save in the database and in the seller dashboard like, it fetches from the database or from the server events, here is i am confused about and again same scenario from seller to user side. And tell me that if i am configuring XMPP also, what is its work flow? basically i am building first time chat application and i did not know about much of it? give me complete guide of ts road map and keep in mind especially a scenario which i asked firstly?