Fix: NullException for IPScanner & NETBIOS if unkown error occours

Author: BornToBeRoot

Source/NETworkManager.Models/Network/IPScanner.cs

@@ -93,7 +93,7 @@ public void ScanAsync(IEnumerable<(IPAddress ipAddress, string hostname)> hosts,
                     // Start netbios lookup async (if enabled)
                     var netbiosTask = options.NetBIOSEnabled
                         ? NetBIOSResolver.ResolveAsync(host.ipAddress, options.NetBIOSTimeout, cancellationToken)
-                        : Task.FromResult(new NetBIOSInfo());
+                        : Task.FromResult(new NetBIOSInfo(host.ipAddress));
 
                     // Get ping result
                     pingTask.Wait(cancellationToken);
@@ -214,26 +214,34 @@ private Task<PingInfo> PingAsync(IPAddress ipAddress, CancellationToken cancella
 
             for (var i = 0; i < options.ICMPAttempts; i++)
             {
+                // Get timestamp 
+                var timestamp = DateTime.Now;
+                
                 try
                 {
-                    // Get timestamp 
-                    var timestamp = DateTime.Now;
-
                     var pingReply = ping.Send(ipAddress, options.ICMPTimeout, options.ICMPBuffer);
 
                     // Success
                     if (pingReply is { Status: IPStatus.Success })
                     {
-                        // IPv4
-                        if (ipAddress.AddressFamily == AddressFamily.InterNetwork)
-                            return new PingInfo(timestamp, pingReply.Address, pingReply.Buffer.Length,
-                                pingReply.RoundtripTime,
-                                pingReply.Options!.Ttl, pingReply.Status);
-
-                        // IPv6
-                        return new PingInfo(timestamp, pingReply.Address, pingReply.Buffer.Length,
-                            pingReply.RoundtripTime,
-                            pingReply.Status);
+                        switch (ipAddress.AddressFamily)
+                        {
+                            case AddressFamily.InterNetwork:
+                               return new PingInfo(
+                                                            timestamp,
+                                                            pingReply.Address, 
+                                                            pingReply.Buffer.Length,
+                                                            pingReply.RoundtripTime,
+                                                            pingReply.Options!.Ttl, 
+                                                            pingReply.Status);
+                            case AddressFamily.InterNetworkV6:
+                                   return new PingInfo(
+                                                            timestamp, 
+                                                            pingReply.Address,
+                                                            pingReply.Buffer.Length,
+                                                            pingReply.RoundtripTime,
+                                                            pingReply.Status);
+                        }
                     }
 
                     // Failed
@@ -242,14 +250,17 @@ private Task<PingInfo> PingAsync(IPAddress ipAddress, CancellationToken cancella
                 }
                 catch (PingException)
                 {
+                    // Ping failed with unknown status
+                    return new PingInfo(timestamp, ipAddress, IPStatus.Unknown);
                 }
 
                 // Don't scan again, if the user has canceled (when more than 1 attempt)
                 if (cancellationToken.IsCancellationRequested)
                     break;
             }
 
-            return new PingInfo();
+            // Fall back to unknown status
+            return new PingInfo(DateTime.Now, ipAddress, IPStatus.Unknown);
         }, cancellationToken);
     }
 

Source/NETworkManager.Models/Network/NetBIOSInfo.cs

@@ -10,17 +10,18 @@ public class NetBIOSInfo
     /// <summary>
     ///     Constructor for an unreachable host.
     /// </summary>
-    public NetBIOSInfo()
+    public NetBIOSInfo(IPAddress ipAddress)
     {
         IsReachable = false;
+        IPAddress = ipAddress;
     }
 
     /// <summary>
     ///     Constructor for a reachable host.
     /// </summary>
     /// <param name="ipAddress">IP address of the host.</param>
     /// <param name="computerName">Computer name of the host.</param>
-    /// <param name="userName">User name of the host.</param>
+    /// <param name="userName">Username of the host.</param>
     /// <param name="groupName">Group name or domain of the host.</param>
     /// <param name="macAddress">MAC address of the host.</param>
     /// <param name="vendor">Vendor of the host based on the MAC address.</param>
@@ -52,7 +53,7 @@ public NetBIOSInfo(IPAddress ipAddress, string computerName, string userName, st
     public string ComputerName { get; set; }
 
     /// <summary>
-    ///     User name of the host.
+    ///     Username of the host.
     /// </summary>
     public string UserName { get; set; }
 

Source/NETworkManager.Models/Network/NetBIOSResolver.cs

@@ -59,17 +59,17 @@ public static async Task<NetBIOSInfo> ResolveAsync(IPAddress ipAddress, int time
             var receiveTask = udpClient.ReceiveAsync();
 
             if (!receiveTask.Wait(timeout, cancellationToken))
-                return new NetBIOSInfo();
+                return new NetBIOSInfo(ipAddress);
 
             var response = receiveTask.Result;
 
             if (response.Buffer.Length < ResponseBaseLen || response.Buffer[ResponseTypePos] != ResponseTypeNbstat)
-                return new NetBIOSInfo(); // response was too short
+                return new NetBIOSInfo(ipAddress); // response was too short
 
             var count = response.Buffer[ResponseBaseLen - 1] & 0xFF;
 
             if (response.Buffer.Length < ResponseBaseLen + ResponseBlockLen * count)
-                return new NetBIOSInfo(); // data was truncated or something is wrong
+                return new NetBIOSInfo(ipAddress); // data was truncated or something is wrong
 
             var result = ExtractNames(response.Buffer, count);
 
@@ -96,7 +96,7 @@ public static async Task<NetBIOSInfo> ResolveAsync(IPAddress ipAddress, int time
         }
         catch (Exception)
         {
-            return null;
+            return new NetBIOSInfo(ipAddress);
         }
         finally
         {