You could implement a serial 'ring' network. Computer connected to RX if first arduino ("A1"), TX of A1 connected to RX of A2, TX of A2 connected to RX of A3, ... TX of An connected to RX of computer. Then an interrupt task on each arduino detects the address in a message and either receives that message or just forwards the bytes on to the next arduino. You'd think something like this would have been standardized by now, but it hasn't (not that I know of, anyway.) Perhaps the patent issues surrounding token ring networks make it unattractive.
Any ascii you see in tutorials is to make the communications easier to understand. Neither the PC side nor arduino has any requirement that serial bytes be ascii.