You can either use RS-232 or I2C or SPI or PSP or ... to talk between two PICs.

If you use RS-232, and you have only two chips in your little 'network' then it is trivial - just hook TXD to RXD and RXD to TXD. If you send two characters or less, you don't need interrupts - just check for PIR1.5 being set (that is what it is in 18F chips, anyway), then read the characters using HSERIN.

But the problem is - if your chips have only 1 RS-232 port, you have no RS-232 ports left. So, the solution is to use at least one chip that has two RS-232 ports, or to use a chip that has one RS-232 port and one I2C port. Your choice.

My example doesn't use bit-banging. It uses hardware. It uses real interrupts. It works on my chips.