UDP with coroutines crashing unity?

I'm working on a routine to receive UDP packets from an app. The system works fine when I use threading but using co-routines seems to just crash the editor outright on play! Any assistance would be welcomed. Someone suggested that it may be effecting the main thread of the program.

This is the script that crashed the editor.

using UnityEngine; using System.Collections; using System; using System.Text; using System.Net; using System.Net.Sockets; //using System.Threading; using System.IO; using System.Runtime.Serialization; using System.Runtime.Serialization.Formatters.Binary;

public class UdpScript : MonoBehaviour {

 struct MyData
 {
     public char letters;
     public byte byt;
     public float dudX, dudY, dudZ;
     public float NewX, NewY, NewZ;

     public MyData Deserialize(byte[] data)
     {
         MyData result = new MyData();

         using (MemoryStream inputStream = new MemoryStream(data))
         using (BinaryReader reader = new BinaryReader(inputStream))
         {
             this.letters = reader.ReadChar();
             this.letters = reader.ReadChar();
             this.byt = reader.ReadByte();
             this.byt = reader.ReadByte();
             this.dudX = reader.ReadSingle();
             this.dudY = reader.ReadSingle();
             this.dudZ = reader.ReadSingle();
             this.NewX = reader.ReadSingle();
             this.NewY = reader.ReadSingle();
             this.NewZ = reader.ReadSingle();
         }
         return result;
     }
 }

 //private Thread receiveThread;
 private UdpClient udp;
 private bool showData, LoopHold, UdpBool;
 public bool receivingbool;
 public int port;
 public float GyroX, GyroY, GyroZ, AccelX, AccelY, AccelZ, pitch, roll;

 // Use this for initialization
 void Start()
 {
     init();
     initUDP();
 }

 // Update is called once per frame
 void Update()
 {
     //StartCoroutine("TestCo");
     if (Input.GetKeyDown(KeyCode.U))
         UdpBool = !UdpBool;
     while (LoopHold)
         if (UdpBool)
             StartCoroutine("RecieveData");
     if (Input.GetKeyDown(KeyCode.D))
         showData = !showData;
 }

 //initialise values
 void init()
 {
     receivingbool = false;
     showData = false;
     LoopHold = true;
     UdpBool = false;
 }

 //initialise the Udp thread to read data
 void initUDP()
 {
     port = 9900;
     udp = new UdpClient(port);
     //receiveThread = new Thread(new ThreadStart(ReceiveData));
     //receiveThread.IsBackground = true;
     //receiveThread.Start();
 }

 //Display wether part is reciveing data from the digital twin and the accel values for caliration
 void OnGUI()
 {
     if (showData)
     {
         Rect rectObj = new Rect(5, 5, 100, 100);
         GUIStyle style = new GUIStyle();
         style.alignment = TextAnchor.UpperRight;
         GUI.Box(rectObj, "# UDPReceive: port :\n" + port + " #\n"
                 + "\nRecieving Data \n" + receivingbool + " \n"
                 + AccelX + "\n"
                 + AccelY + "\n"
                 + AccelZ, style);   //receivingbool is set when a new udp client starts.
     }
 }

 void ReadKeyInputs()
 {
     if (Input.GetKeyDown(KeyCode.D))
         showData = !showData;
 }

 // receive thread
 IEnumerator RecieveData()
 {
       try
       {
         IPEndPoint anyIP = new IPEndPoint(IPAddress.Any, 0);
         byte[] data = udp.Receive(ref anyIP);
         MyData latestPacket = new MyData();
         latestPacket.Deserialize(data);
         GyroX = latestPacket.NewX;
         GyroY = latestPacket.NewY;
         GyroZ = latestPacket.NewZ;
         AccelX = latestPacket.dudX;
         AccelY = latestPacket.dudY;
         AccelZ = latestPacket.dudZ;
       }
       catch (Exception err)                                       //basic error handling, not particularly robust
       {
           print(err.ToString());
       }
         yield return null; 
 }

 IEnumerator TestCo()
 {
     Debug.LogWarning("tips");
     yield return null;
 }

 //close the UdpClient
 public void EndClient()
 {
     if (receivingbool)
     {
         //if (receiveThread.IsAlive)
         //    receiveThread.Abort();                      //Stop the curent thread
         udp.Close();                                //Close the whole client to avoid memory leaks 
         udp = null;
     }//set the address off the previous client to null
     LoopHold = false;
 }

}

I'm using co-routines as WebGL and Unity aren't thread-safe.