Chat - Visualize Message

Hey guys, I’m developing a read system for a chat. Every message sent have a ‘read = false’ attribute. How can I know if the other user entered the chat page so I can change to ‘read = true’? I have no idea…

HELP ME! :’(

You have to send a response message from the receiver to the sender, telling him that msg with id=**** has been received / open / whatever