I am wondering how the apps that allow a user to choose an item and, once the user has selected an item and checked out, give the retailer information about order that has been placed.
For example, say a takeaway has an iOS app and customer has chosen fish and chips and placed an order.
How does the takeaway know an order has been placed? If it's TCP IP then I guess we need to start a server on the takeaway's computer? Is that right?
How can modify the menu without making any changes in app from developer side?
I am looking for an answer about how things work in real world. Once I have the idea then developing it is a piece of cake.