Hello Sulax,
Your problem is the 8051 only supports one start bit, 8 data bits, parity (if set up), and a stop bit.
You are trying to receive 2400 baud, even parity, 7 data bits and one stop bit. (2400 / E / 7 / 1).
You can bit bang the solution out or go external hardware.
Good luck,
Charles Bannister