do two I/O microcontroller pins that are connected to each other require an external resistor?
P1.2 to P1.7 and P3.0 to P3.5 have internal pullups, so you don't need external resistors unless the rise time is too slow (long cable + high bit rate?). 

P1.0 and P1.1 don't have internal pullups, but as you aren't using them you can just set them to output low so they don't don't 'float'. 

Unlike more modern MCUs the 8051's port pins are not actively driven high, so you don't need series resistors to prevent damage if they are short circuited to Ground or another output.