Use the Task-based asynchonous model

VirtualMeetingMonitor/App.config

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8" ?>
 <configuration>
     <startup> 
-        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5.2" />
+        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.7.2" />
     </startup>
 </configuration>

VirtualMeetingMonitor/Form.cs

@@ -2,6 +2,7 @@
 using System.Diagnostics;
 using System.Drawing;
 using System.IO;
+using System.Threading.Tasks;
 using System.Windows.Forms;
 
 namespace VirtualMeetingMonitor
@@ -13,7 +14,7 @@ public partial class Form : System.Windows.Forms.Form
         private readonly VirtualMeeting meeting = new VirtualMeeting();
         readonly Timer timer = new Timer();
         private const string LogFileName = "meetings.txt";
-
+        private Task networkListener;
 
         public Form()
         {
@@ -27,7 +28,7 @@ public Form()
             timer.Tick += OnTimerEvent;
 
             network.OutsideUDPTafficeReceived += Network_OutsideUDPTafficeReceived;
-            network.StartListening();
+            networkListener = network.StartListening();
 
             meeting.OnMeetingStarted += Meeting_OnMeetingStarted;
             meeting.OnMeetingEnded += Meeting_OnMeetingEnded;
@@ -141,9 +142,11 @@ private void OnTimerEvent(object sender, EventArgs e)
             meeting.CheckMeetingStatus();
         }
 
-        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
+        private async void Form1_FormClosing(object sender, FormClosingEventArgs e)
         {
             network.Stop();
+            //By awaiting the network listening task, we ensure that the task can be disposed, releasing its resources.
+            await networkListener;
         }
 
         private void openLogToolStripMenuItem_Click(object sender, EventArgs e)

VirtualMeetingMonitor/Network.cs

@@ -2,6 +2,7 @@
 using System.Linq;
 using System.Net;
 using System.Net.Sockets;
+using System.Threading.Tasks;
 
 namespace VirtualMeetingMonitor
 {
@@ -17,22 +18,53 @@ class Network
         public event Notify OutsideUDPTafficeReceived;
 
 
-        public void StartListening()
+        public async Task StartListening()
         {
+            SetupLocalIp();
+            ConfigureSocket();
 
-            IPHostEntry HosyEntry = Dns.GetHostEntry((Dns.GetHostName()));
-            if (HosyEntry.AddressList.Any())
+            //Start receiving the packets asynchronously
+            await ProcessPackets();
+        }
+
+        /// <summary>
+        /// Use the socket to receive data. Simply loop until the socket is disposed.
+        /// </summary>
+        /// <returns></returns>
+        private async Task ProcessPackets()
+        {
+            //Declare the buffer outside the loop so that do not recreate it every time we go around the loop.
+            ArraySegment<byte> buffer = new ArraySegment<byte>(byteData);
+
+            while (true)
             {
-                foreach (IPAddress ip in HosyEntry.AddressList)
+                try
                 {
-                    if (ip.AddressFamily == AddressFamily.InterNetwork)
-                    {
-                        localIp = ip;
-                        break;
-                    }
+                    // At this point the socket will wait for data to arrive. Awaiting here means
+                    // control is returned to the main UI until there is data to process.
+                    // This is *not* the same as blocking, but we can use the same mental model
+                    // as if it was a blocking call.
+                    int bytesReceived = await mainSocket.ReceiveAsync(buffer, SocketFlags.None);
+                    ParseData(byteData, bytesReceived);
+                }
+                catch (ObjectDisposedException)
+                {
+                    // This exception occurs when the application is stopping and the socket is closed.
+                    // This signals that we should exit the loop.
+                    return;
+                }
+                catch (Exception ex)
+                {
+                    Console.WriteLine("OnReceive Exception: " + ex.Message);
                 }
             }
+        }
 
+        /// <summary>
+        /// Configures the listening socket.
+        /// </summary>
+        private void ConfigureSocket()
+        {
             //For sniffing the socket to capture the packets has to be a raw socket, with the
             //address family being of type internetwork, and protocol being IP
             mainSocket = new Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.IP);
@@ -44,42 +76,37 @@ public void StartListening()
             //Set the socket  options
             mainSocket.SetSocketOption(SocketOptionLevel.IP, SocketOptionName.HeaderIncluded, true);
 
-            byte[] True = new byte[] { 1, 0, 0, 0 };
-            byte[] Out = new byte[] { 1, 0, 0, 0 }; //Capture outgoing packets
+            byte[] True = new byte[] {1, 0, 0, 0};
+            byte[] Out = new byte[] {1, 0, 0, 0}; //Capture outgoing packets
 
             //Socket.IOControl is analogous to the WSAIoctl method of Winsock 2
             // The current user must belong to the Administrators group on the local computer
             mainSocket.IOControl(IOControlCode.ReceiveAll, True, Out);
-
-            //Start receiving the packets asynchronously
-            mainSocket.BeginReceive(byteData, 0, byteData.Length, SocketFlags.None, OnReceive, null);
         }
 
-        public void Stop()
+        /// <summary>
+        /// Set up a local IP address from the list of available addresses.
+        /// The first available IPv4 is chosen as the local IP address.
+        /// </summary>
+        private void SetupLocalIp()
         {
-            mainSocket.Close();
-        }
-
-        private void OnReceive(IAsyncResult ar)
-        {
-            try
-            {
-                int nReceived = mainSocket.EndReceive(ar);
-                ParseData(byteData, nReceived);
-            }
-            catch (Exception ex)
+            IPHostEntry HosyEntry = Dns.GetHostEntry((Dns.GetHostName()));
+            if (HosyEntry.AddressList.Any())
             {
-                Console.WriteLine("OnReceive Exception: " + ex.Message);
+                foreach (IPAddress ip in HosyEntry.AddressList)
+                {
+                    if (ip.AddressFamily == AddressFamily.InterNetwork)
+                    {
+                        localIp = ip;
+                        break;
+                    }
+                }
             }
+        }
 
-            try
-            {
-                //Another call to BeginReceive so that we continue to receive the incoming packets
-                mainSocket.BeginReceive(byteData, 0, byteData.Length, SocketFlags.None, OnReceive, null);
-            }
-            catch (ObjectDisposedException)
-            {
-            }
+        public void Stop()
+        {
+            mainSocket.Close();
         }
 
         private void ParseData(byte[] byteData, int nReceived)
@@ -91,7 +118,6 @@ private void ParseData(byte[] byteData, int nReceived)
             }
         }
 
-
         private bool isOutsideUDPTaffice(IPHeader ipHeader)
         {
             bool retVal = false;
@@ -107,7 +133,5 @@ private bool isOutsideUDPTaffice(IPHeader ipHeader)
             }
             return retVal;
         }
-
-
     }
 }

VirtualMeetingMonitor/VirtualMeetingMonitor.csproj

@@ -9,7 +9,7 @@
     <AppDesignerFolder>Properties</AppDesignerFolder>
     <RootNamespace>VirtualMeetingMonitor</RootNamespace>
     <AssemblyName>VirtualMeetingMonitor</AssemblyName>
-    <TargetFrameworkVersion>v4.5.2</TargetFrameworkVersion>
+    <TargetFrameworkVersion>v4.7.2</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
     <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
   </PropertyGroup>