Unity Not Executing Network Commands

I am making a very simple multiplayer 2D game with 2 players, I decided to make my own networking solution as I have experience in that area, nothing complicated. However, I cannot figure out why unity will not execute the commands I am sending it via UDP.

I have a gameobject in my scene which I attached the networking code to, the expected behaviour is that I send a "connected" string to Unity (which works fine and Unity reads it properly) but whenever I try to execute ANY Unity function after that, it just does not work. I get no crashes, no error messages, nothing, it just kind of hangs and I am not able to send any more commands either.

Code (CSharp):

1. using System;
2. using UnityEngine;
3. using System.Net;
4. using System.Text;
5. using System.Net.Sockets;
6.  
7. [RequireComponent(typeof(HostFunctions))]
8. public class Host : MonoBehaviour
9. {
10.     [Header("Network Settings")]
11.     public string host = "127.0.0.1";
12.     public int port = 6542;
13.  
14.     [Header("Game Settings")]
15.     public GameObject playerPrefab;
16.  
17.     HostFunctions functions;
18.     UdpClient server;
19.     IPEndPoint sender;
20.     const int bufferSize = 1024 * 4;
21.     byte[] buffer = new byte[bufferSize];
22.  
23.     void Start()
24.     {
25.         functions = GetComponent<HostFunctions>();
26.         server = new UdpClient(new IPEndPoint(IPAddress.Parse(host), port));
27.         sender = new IPEndPoint(IPAddress.Any, 0);
28.         server.BeginReceive(ReceiveCallback, null);
29.         Debug.Log("Started listening @ " + server.Client.LocalEndPoint);
30.     }
31.  
32.     void ReceiveCallback(IAsyncResult result)
33.     {
34.         buffer = server.EndReceive(result, ref sender);
35.         string bufString = Encoding.Default.GetString(buffer).Replace("\0", "");
36.  
37.         Debug.Log(bufString);
38.  
39.         if(bufString.Equals("connected"))
40.         {
41.              // This is where the issue occurs, if I remove this line of code, everything will work fine
42.             // but will not instantiate the playerPrefab object. No other Unity function will work either.
43.             Instantiate(playerPrefab, new Vector3(1, 0, 0), new Quaternion(0, 0, 0, 0));
44.         }
45.  
46.         server.BeginReceive(ReceiveCallback, null);
47.     }
48.  
49.     void OnApplicationQuit()
50.     {
51.         if(server != null)
52.         {
53.             server.Close();
54.             server.Dispose();
55.         }
56.     }
57. }