Serial between two 8051

Hey Guys, I searched in the forum about a similar problem and I found, but It does not have the solution for the problem. The question is how to connect two uC 8051 using the serial ports. Like the other topic, it works on Proteus but it does not work on breadboard.
Using a AD converter I have a potentiometer, turning on 8 leds to indicate a level.

You will have to post your code and Proteus project.
If it works in Proteus it is probably a wiring error.
Have you got a common ground ?
Are you SURE TX goes to RX and Rx goes to TX