feat: return correct config for CS processors

When MC is running on a processor with a control subnet and a user
attempts to access the UI via the control subnet, the return _config.local.json
needs to reflect the CS LAN IP address for the processor rather than the LAN IP Address.

In order to accomplish this, there will now be 2 config files written to disk on startup:
1. the original file, /user/programX/mcUserApp/_local-config/_config.local.json
2. A file with the correct CS IP Address /user/programX/mcUserApp/_local-config/_config.cs.json

When a user requests the _config.local.json, the processor will compare the remote IP address
with the CS LAN IP Address and determine if they're in the same subnet, the assumption being
that if the IP Addresses are in the same subnet, then the app or end user is on the CS LAN and needs the CS config.
If the addresses are in the same subnet, then the contents of the _config.cs.json will be returned.

src/PepperDash.Essentials.Core/Extensions/IpAddressExtensions.cs

@@ -0,0 +1,86 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace PepperDash.Essentials.Core
+{
+    /// <summary>
+    /// Exnsions for IPAddress to provide additional functionality such as getting broadcast address, network address, and checking if two addresses are in the same subnet.
+    /// </summary>
+    public static class IPAddressExtensions
+    {
+        /// <summary>
+        /// Get the broadcast address for a given IP address and subnet mask.
+        /// </summary>
+        /// <param name="address">Address to check</param>
+        /// <param name="subnetMask">Subnet mask in a.b.c.d format</param>
+        /// <returns>Broadcast address</returns>
+        /// <remarks>
+        /// If the input IP address is 192.168.1.100 and the subnet mask is 255.255.255.0, the broadcast address will be 192.168.1.255
+        /// </remarks>
+        /// <exception cref="ArgumentException"></exception>
+        public static IPAddress GetBroadcastAddress(this IPAddress address, IPAddress subnetMask)
+        {
+            byte[] ipAdressBytes = address.GetAddressBytes();
+            byte[] subnetMaskBytes = subnetMask.GetAddressBytes();
+
+            if (ipAdressBytes.Length != subnetMaskBytes.Length)
+                throw new ArgumentException("Lengths of IP address and subnet mask do not match.");
+
+            byte[] broadcastAddress = new byte[ipAdressBytes.Length];
+            for (int i = 0; i < broadcastAddress.Length; i++)
+            {
+                broadcastAddress[i] = (byte)(ipAdressBytes[i] | (subnetMaskBytes[i] ^ 255));
+            }
+            return new IPAddress(broadcastAddress);
+        }
+
+        /// <summary>
+        /// Get the network address for a given IP address and subnet mask.
+        /// </summary>
+        /// <param name="address">Address to check</param>
+        /// <param name="subnetMask">Subnet mask in a.b.c.d</param>
+        /// <returns>Network Address</returns>
+        /// /// <remarks>
+        /// If the input IP address is 192.168.1.100 and the subnet mask is 255.255.255.0, the network address will be 192.168.1.0
+        /// </remarks>
+        /// <exception cref="ArgumentException"></exception>
+        public static IPAddress GetNetworkAddress(this IPAddress address, IPAddress subnetMask)
+        {
+            byte[] ipAdressBytes = address.GetAddressBytes();
+            byte[] subnetMaskBytes = subnetMask.GetAddressBytes();
+
+            if (ipAdressBytes.Length != subnetMaskBytes.Length)
+                throw new ArgumentException("Lengths of IP address and subnet mask do not match.");
+
+            byte[] broadcastAddress = new byte[ipAdressBytes.Length];
+            for (int i = 0; i < broadcastAddress.Length; i++)
+            {
+                broadcastAddress[i] = (byte)(ipAdressBytes[i] & (subnetMaskBytes[i]));
+            }
+            return new IPAddress(broadcastAddress);
+        }
+
+        /// <summary>
+        /// Determine if two IP addresses are in the same subnet.
+        /// </summary>
+        /// <param name="address2">Address to check</param>
+        /// <param name="address">Second address to check</param>
+        /// <param name="subnetMask">Subnet mask to use to compare the 2 IP Address</param>
+        /// <returns>True if addresses are in the same subnet</returns>
+        /// <remarks>
+        /// If the input IP addresses are 192.168.1.100 and 192.168.1.200, and the subnet mask is 255.255.255.0, this will return true.
+        /// If the input IP addresses are 10.1.1.100 and 192.168.1.100, and the subnet mask is 255.255.255.0, this will return false.
+        /// </remarks>
+        public static bool IsInSameSubnet(this IPAddress address2, IPAddress address, IPAddress subnetMask)
+        {
+            IPAddress network1 = address.GetNetworkAddress(subnetMask);
+            IPAddress network2 = address2.GetNetworkAddress(subnetMask);
+
+            return network1.Equals(network2);
+        }
+    }
+}

src/PepperDash.Essentials.MobileControl/WebSocketServer/MobileControlWebsocketServer.cs

@@ -60,47 +60,9 @@ namespace PepperDash.Essentials.WebSocketServer
 
         private string lanIpAddress => CrestronEthernetHelper.GetEthernetParameter(CrestronEthernetHelper.ETHERNET_PARAMETER_TO_GET.GET_CURRENT_IP_ADDRESS, CrestronEthernetHelper.GetAdapterdIdForSpecifiedAdapterType(EthernetAdapterType.EthernetLANAdapter));
 
-        private string csIpAddress
+        private System.Net.IPAddress csIpAddress;     
-        {
-            get
-            {
-                short csAdapterId = -1;
 
-                try
+        private System.Net.IPAddress csSubnetMask;
-                {
-                    CrestronEthernetHelper.GetAdapterdIdForSpecifiedAdapterType(EthernetAdapterType.EthernetCSAdapter);
-                }
-                catch (ArgumentException)
-                {
-                    return "";
-                }
-
-                return CrestronEthernetHelper.GetEthernetParameter(CrestronEthernetHelper.ETHERNET_PARAMETER_TO_GET.GET_CURRENT_IP_ADDRESS, csAdapterId);
-            }
-        }
-
-        private string csSubnet
-        {
-            get
-            {
-                short csAdapterId = -1;
-
-                try
-                {
-                    CrestronEthernetHelper.GetAdapterdIdForSpecifiedAdapterType(EthernetAdapterType.EthernetCSAdapter);
-                }
-                catch (ArgumentException)
-                {
-                    return "";
-                }
-
-                var subnetMask = CrestronEthernetHelper.GetEthernetParameter(CrestronEthernetHelper.ETHERNET_PARAMETER_TO_GET.GET_CURRENT_IP_MASK, csAdapterId);
-
-                this.LogDebug("cs subnet mask: {subnetMask}", subnetMask);
-
-                return subnetMask;
-            }
-        }
 
         /// <summary>
         /// The path for the WebSocket messaging
@@ -162,8 +124,6 @@ namespace PepperDash.Essentials.WebSocketServer
             // Set the default port to be 50000 plus the slot number of the program
             Port = 50000 + (int)Global.ControlSystem.ProgramNumber;            
 
-            this.LogDebug("CS Subnet: {csSubnet}", csSubnet);
-
             if (customPort != 0)
             {
                 Port = customPort;
@@ -173,9 +133,6 @@ namespace PepperDash.Essentials.WebSocketServer
             {
                 try
                 {
-                    CrestronEthernetHelper.GetAdapterdIdForSpecifiedAdapterType(EthernetAdapterType.EthernetCSAdapter);
-
-
                     Debug.LogMessage(LogEventLevel.Information, "Automatically forwarding port {0} to CS LAN", Port);
 
                     var csAdapterId = CrestronEthernetHelper.GetAdapterdIdForSpecifiedAdapterType(EthernetAdapterType.EthernetCSAdapter);
@@ -198,6 +155,23 @@ namespace PepperDash.Essentials.WebSocketServer
                 }
             }
 
+            try
+            {                
+                var csAdapterId = CrestronEthernetHelper.GetAdapterdIdForSpecifiedAdapterType(EthernetAdapterType.EthernetCSAdapter);
+                var csSubnetMask = CrestronEthernetHelper.GetEthernetParameter(CrestronEthernetHelper.ETHERNET_PARAMETER_TO_GET.GET_CURRENT_IP_MASK, csAdapterId); 
+                var csIpAddress = CrestronEthernetHelper.GetEthernetParameter(CrestronEthernetHelper.ETHERNET_PARAMETER_TO_GET.GET_CURRENT_IP_ADDRESS, csAdapterId);
+
+                this.csSubnetMask = System.Net.IPAddress.Parse(csSubnetMask);
+                this.csIpAddress = System.Net.IPAddress.Parse(csIpAddress);
+            }
+            catch (ArgumentException)
+            {
+                if (parent.Config.DirectServer.AutomaticallyForwardPortToCSLAN == false)
+                {
+                    Debug.LogMessage(LogEventLevel.Information, "This processor does not have a CS LAN", this);
+                }
+            }
+
 
             UiClients = new Dictionary<string, UiClientContext>();
 
@@ -382,6 +356,8 @@ namespace PepperDash.Essentials.WebSocketServer
                 // Write the LAN application configuration file. Used when a request comes in for the application config from the LAN 
                 var lanAdapterId = CrestronEthernetHelper.GetAdapterdIdForSpecifiedAdapterType(EthernetAdapterType.EthernetLANAdapter);
 
+                this.LogDebug("LAN Adapter ID: {lanAdapterId}", lanAdapterId);
+
                 var processorIp = CrestronEthernetHelper.GetEthernetParameter(CrestronEthernetHelper.ETHERNET_PARAMETER_TO_GET.GET_CURRENT_IP_ADDRESS, lanAdapterId);                
 
                 var config = GetApplicationConfig(processorIp);
@@ -408,6 +384,8 @@ namespace PepperDash.Essentials.WebSocketServer
                 return;
             }
 
+            this.LogDebug("CS LAN Adapter ID: {csAdapterId}. Adding CS Config", csAdapterId);
+
             using (var sw = new StreamWriter(File.Open($"{userAppPath}{localConfigFolderName}{Global.DirectorySeparator}{appConfigCsFileName}", FileMode.Create, FileAccess.ReadWrite)))
             {
                 // Write the CS application configuration file. Used when a request comes in for the application config from the CS
@@ -1121,7 +1099,13 @@ namespace PepperDash.Essentials.WebSocketServer
 
             this.LogVerbose("Attempting to serve file: {filePath}", filePath);
 
+            var remoteIp = req.RemoteEndPoint.Address;
 
+            // Check if the request is coming from the CS LAN and if so, send the CS config instead of the LAN config
+            if (csSubnetMask != null && csIpAddress != null && remoteIp.IsInSameSubnet(csIpAddress, csSubnetMask) && filePath.Contains(appConfigFileName))
+            {
+                filePath = filePath.Replace(appConfigFileName, appConfigCsFileName);
+            }
 
             byte[] contents;
             if (File.Exists(filePath))