I am building a SAAS cloud service for restaurants.
Assume a specific restaurant has two handheld devices for creating orders and updating orders, these handheld devices talk with the cloud server.

my question is what is an appropriate design so that both devices can get updated order status from server near real-time?

I am currently considering two approaches: long polling and web socket;

1. long polling can do it, each device can keep calling the server, but the worry is long polling consumes too much resources;
2. i have done some research on web socket, but have not found how to sync one account with 2 client devices yet.

I would appreciate any input/help here.

thanks in advance!