Package for using serial communication in Unity3d in Windows
Pair your port with you computer.
Add SerialCOM to a GameObjct.
Use SerialWrapper script to read or write data.
In Player Settings -> other Settings use .NET 4.x
Add unityPackage to Unity, in folder serial communication you will find a scene "New Scene" to test the COM port (teseted on Arduino uno, nano).
For the incoming data, SerialCOM script reads till new line appears ('\n').