Sandun, unlike in analogue communication, digital communication is less prone to distortions such as attenuation. Since RS232 is used here with close proximity, I don't think you need to think that deep to design this. Just start working with two level shifters such as MAX232 and I'm sure those will manage the communication for you. Be sure to use a shielded cable. I'm fully sure this setup can be designed to work without trouble.
You can also look at USB, RS422 or RS485 communication. All of them use differential signalling making them more effective for industrial environments.
See How differential signalling helps suppressing noiseRS 232 / RS485 / RS422 - what's difference?