Hi,

An impossible task with a PIC microcontroller.
(You will need a 32bit MCU).

To develop from scratch a product like that, a group
of ten engineers will have to work about two years if
they use a chipset made for Power Line Communications
and if they buy the TCP/IP networking software.

Powerline Communication Chipset:
http://pdfserv.maxim-ic.com/en/ad/MAX2986-AD.pdf

Best regards,

Luciano