Get all offline messages of the perticular resource

My app supports multiple client login to the user, basically one user can login from different device like ios, android and web.
I am able to get offline messages when user is logged in from only one device.
Now I want to get all chats which is missed in perticular resource like if user had chat from ios device when android one was not online but after some time when user goes to online from android I want to get all chat of user had on ios.

I installed monitoring plugin to my openfire server.

Please someone suggest me how to solve this issue.