Unity hangs when I press play (serial port, unity + arduino)

Hi all, I have a script that gets values from a serial port from an Arduino, however when I hit play, unity editor hangs. How do I fix this? Thanks!

(this is my code for unity)

 using UnityEngine;
 using System.Collections;
 using System.IO.Ports;
 using System.IO;
 using System;
 using System.Linq;
 using System.Collections;
 using System.Collections.Generic;
 
 public class musicScrip : MonoBehaviour {
 
     private float amount;
     private int var1;
     private int var2;
     private int var3;
 
 
     SerialPort sp = new SerialPort("COM7", 9600);
 
     void Start ()
     {
         sp.Open();
         sp.ReadTimeout = 100;
 
     }
     
     void Update () 
     {
         if (sp.IsOpen)  //youtube tutorial's method 
         {
             try
             {
                 serialEvent (sp);
             }
             catch (System.Exception)
             {
                 throw;
             }
         }
 
     }
 
     void serialEvent(SerialPort myPort)
     {
         string myString = myPort.ReadLine(); //the ascii value of the "|" character
         if(myString != null)
         {
             myString = myString.Trim(); //remove whitespace around our values
             string[] inputs = myString.Substring(2, myString.Length-4).Split(',');
             //now assign your values in processing
             if(inputs.Length == 3)
             {
                 var1 = Int32.Parse(inputs[0]);
                 var2 = Int32.Parse(inputs[1]);
                 var3 = Int32.Parse(inputs[2]);
                 Debug.Log(var1);
         
             
             }
 
         }
     }
 }