Resistors may be placed in appropriate places, if current- limiting is a concern. This should not be a problem. The bus ground line should of course be grounded along with the emitter. Directly tie the output to DATA1 and ground. This may be dangerous and destroy your parallel port, but they are cheap.
Incoming bits trigger an interrupt which is time stamped in the interrupt handler.
These are decoded every time the timer tick runs, which depends on the system. A start of packet is signaled by a minimum of 2400 ms of high, followed by a 600 ms low. The end of packet is a minimum of 4200 ms low. Generally no high quality automation is possible. The start bit is high for 2400 ms and low for 400 ms.