In this case, you'll stick to a single Integer field which will be used as a unique identifier and enable you to track the progress of a message through the grid.
In about 200 cases, the developer created a way to track a device's identifier code; the other apps used this functionality from advertising or tracking software library.
They are assigned a process id or a numerical identifier so that the operating system may keep track of the programs currently executing and of their associated priority levels.