I am working on an application where I am required to communicate with 6 Arduino Unos from one master Arduino Uno. the six Arduino boards are placed at the 1-meter distance from the main Arduino Uno. Therefore I cannot use SPI or I2C am I correct? is this possible to do with software UARTs in Arduino Uno? 6 UARTs communication with software serial? if this is not possible how to do this?
My recommendation is to use RS485. RS485, instead of RS232 (The Serial you are using), is a protocol that enables several devices communicated on the same serial line.
For you to use this, you need to buy 6 RS485 IC, each one connecting directly to the regular serial port of the Arduino. RS485 works the same as RS232 Serial, but is an half-duplex channel where several devices can connect at the same time.