Detect Multiple Touch

In my game, I control an object using touch event. When I touch the right half of the screen, the object rotates, when I touch the left half of the screen, the object moves.  It works perfectly when it’s a single touch, but when I touch any side of the screen and then start touching the other side at the same time,  it results in an unexpected, mixed-up behavior.

I guess my question is, how to separate or differentiate multiple touches one from the other. 

system.activate( "multitouch" ) onTouch = function (event) if (event.phase == "began") then         pX = event.x -- Get start X position of the touch         print( "ID:"..tostring(event.id) )         if (event.x \> centerX) then --if the touch is in the right or left half of the screen             xPos = "right"         else              xPos = "left"         end elseif (event.phase == "moved") then local dX = (event.x - pX )  if (xPos == "right") then            rotatePlayer(dx)         else              movePlayer(dX)     end

https://forums.coronalabs.com/topic/66142-how-to-handle-user-touching-the-move-forward-button-and-jump-button-at-the-same-time/#entry342396

https://forums.coronalabs.com/topic/66142-how-to-handle-user-touching-the-move-forward-button-and-jump-button-at-the-same-time/#entry342396