Man the dropkick trolls why do they even bother to post, oh wait they are trying to be funny .. legends in their own lunchboxes.
Anyhow the answer to your question in unity this will get you started you will need to change the com3 and baud rate to whatever port and speed you need
using UnityEngine;
using System.Collections;
using System.IO.Ports;
public class serialControlBasic : MonoBehaviour {
SerialPort stream;
void Start () {
stream = new SerialPort("COM3", 9600);
stream.Open();
}
void Update () {
}
}
A small Arduino test code will something like
void setup(){
Serial.begin(9600);
}
void loop(){
Serial.println(random(1,1000));
delay(10);
}