Moved priority of callbacks.
Restructured appending of listener.
Added error if port is already opened.
Calling callbacks before the global event emit.
Changed error text.
Added double NOT.
Added check for negative delays.
Added and changed error texts.
Rewrote data callback from send.
Fixed typeof check.
Removed some indentation levels.
Added some returns.
Made data parameter optional.
Made callback parameters optional.
Refactored setup code.
Refactored NoOperation code.