I guess what I'm asking is say I have a device that can generate a stream of numbers, integers, nothing fancy. I want random integers with no limit to the size

I guess what I'm asking is say I have a device that can generate a stream of numbers, integers, nothing fancy. I want random integers with no limit to the size returned, a truly random number and by that I mean a true random integer without any limitation in size. Really I guess I'm trying to grasp how a true random anything could exist or more to the point how a person could make a device or even be able to know if a random number or anything has been returned as a result.