Possible for them to be called at multiple times.

NetworkTablesCore.Test/TestNetworkTableAPIListeners.cs

@@ -27,12 +27,12 @@ internal class MockConnectionListener : IRemoteConnectionListener
         public IRemote ConnectedRemote = null;
         public IRemote DisconnectedRemote = null;
 
-        public void Connected(IRemote remote)
+        public void Connected(IRemote remote, ConnectionInfo info)
         {
             ConnectedRemote = remote;
         }
 
-        public void Disconnected(IRemote remote)
+        public void Disconnected(IRemote remote, ConnectionInfo info)
         {
             DisconnectedRemote = remote;
         }

NetworkTablesCore/Native/CoreMethods.cs

@@ -525,13 +525,19 @@ internal static void StopClient()
             StopRpcServer();
             StopNotifier();
             Interop.NT_StopClient();
+            //Clear callback dictionaries
+            s_entryCallbacks.Clear();
+            s_connectionCallbacks.Clear();
         }
 
         internal static void StopServer()
         {
             StopRpcServer();
             StopNotifier();
             Interop.NT_StopServer();
+            //Clear callback dictionaries
+            s_entryCallbacks.Clear();
+            s_connectionCallbacks.Clear();
         }
 
         internal static void StopNotifier()

NetworkTablesCore/Native/Interop.cs

@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using System.Reflection;
 using System.Runtime.InteropServices;
 using System.Security;
 // ReSharper disable InconsistentNaming
@@ -20,6 +21,9 @@ internal class Interop
         // ReSharper disable PrivateFieldCanBeConvertedToLocalVariable
         private static readonly IntPtr s_library;
         private static readonly ILibraryLoader s_loader;
+        private static readonly OsType s_osType;
+        private static string s_libraryLocation = null;
+        private static bool s_useCommandLineFile = false;
         // ReSharper restore PrivateFieldCanBeConvertedToLocalVariable
 
         static Interop()
@@ -28,8 +32,6 @@ static Interop()
             {
                 try
                 {
-                    bool useCommandLineFile = false;
-                    string extractedLocation = null;
 
                     string[] commandArgs = Environment.GetCommandLineArgs();
                     foreach (var commandArg in commandArgs)
@@ -44,33 +46,56 @@ static Interop()
                             //If the file exists, just return it so dlopen can load it.
                             if (File.Exists(file))
                             {
-                                extractedLocation = file;
-                                useCommandLineFile = true;
+                                s_libraryLocation = file;
+                                s_useCommandLineFile = true;
                             }
                         }
                     }
-                    OsType type = LoaderUtilities.GetOsType();
+                    s_osType = LoaderUtilities.GetOsType();
 
-                    if (!useCommandLineFile)
+                    if (!s_useCommandLineFile)
                     {
-                        
-                        if (!LoaderUtilities.CheckOsValid(type))
+
+                        if (!LoaderUtilities.CheckOsValid(s_osType))
                             throw new InvalidOperationException("OS Not Supported");
 
                         string embeddedResourceLocation;
-                        LoaderUtilities.GetLibraryName(type, out embeddedResourceLocation, out extractedLocation);
+                        LoaderUtilities.GetLibraryName(s_osType, out embeddedResourceLocation, out s_libraryLocation);
 
                         bool successfullyExtracted = LoaderUtilities.ExtractLibrary(embeddedResourceLocation,
-                            extractedLocation);
+                            ref s_libraryLocation);
 
                         if (!successfullyExtracted)
                             throw new FileNotFoundException(
                                 "Library file could not be found in the resorces. Please contact RobotDotNet for support for this issue");
                     }
 
-                    s_library = LoaderUtilities.LoadLibrary(extractedLocation, type, out s_loader);
+                    if (s_osType == OsType.Armv7HardFloat)
+                    {
+                        //Make sure the proper libstdc++.so.6 gets extracted.
+                        string resourceLocation = "NetworkTables.NativeLibraries.armv7.libstdc++.so";
+                        string extractLoc = "libstdc++.so.6";
+                        LoaderUtilities.ExtractLibrary(resourceLocation, ref extractLoc);
+                    }
 
-                    if (s_library == IntPtr.Zero) throw new BadImageFormatException($"Library file {extractedLocation} could not be loaded successfully.");
+                    s_library = LoaderUtilities.LoadLibrary(s_libraryLocation, s_osType, out s_loader);
+
+                    if (s_library == IntPtr.Zero)
+                    {
+                        if (s_osType == OsType.Armv7HardFloat)
+                        {
+                            //We are arm v7. We might need the special libstdc++.so.6;
+                            Console.WriteLine("You are on an Arm V7 device. On most of these devices, a " 
+                                + "special library needs to be loaded. This library has been extracted" +
+                                " to the current directory. Please prepend your run command with\n" + 
+                                "env LD_LIBRARY_PATH=.:LD_LIBRARY_PATH yourcommand\nand run again.");
+                            throw new InvalidOperationException("Follow the instructions printed above to solve this error.");
+                        }
+                        else
+                        {
+                            throw new BadImageFormatException($"Library file {s_libraryLocation} could not be loaded successfully.");
+                        }
+                    }
 
                     InitializeDelegates(s_library, s_loader);
                 }
@@ -82,8 +107,10 @@ static Interop()
                 }
                 s_libraryLoaded = true;
 
-                //Adds our unload code.
+                //Adds our unload code. OK to set both as only 1
+                //Will ever get called.
                 AppDomain.CurrentDomain.ProcessExit += OnProcessExit;
+                AppDomain.CurrentDomain.DomainUnload += OnProcessExit;
             }
         }
 
@@ -96,6 +123,22 @@ private static void OnProcessExit(object sender, EventArgs e)
             NT_StopServer();
             NT_StopRpcServer();
             NT_StopNotifier();
+
+            s_loader.UnloadLibrary(s_library);
+
+            try
+            {
+                //Don't delete file if we are using a specified file.
+                if (!s_useCommandLineFile && File.Exists(s_libraryLocation))
+                {
+                    File.Delete(s_libraryLocation);
+                }
+            }
+            catch
+            {
+                //Any errors just ignore.
+            }
+            
         }
 
         private static void InitializeDelegates(IntPtr library, ILibraryLoader loader)

NetworkTablesCore/Native/LibraryLoader.cs

@@ -7,6 +7,8 @@ internal interface ILibraryLoader
     {
         IntPtr LoadLibrary(string filename);
         IntPtr GetProcAddress(IntPtr dllHandle, string name);
+
+        void UnloadLibrary(IntPtr handle);
     }
 
     [ExcludeFromCodeCoverage]
@@ -28,11 +30,19 @@ IntPtr ILibraryLoader.GetProcAddress(IntPtr dllHandle, string name)
             return addr;
         }
 
+        void ILibraryLoader.UnloadLibrary(IntPtr handle)
+        {
+            FreeLibrary(handle);
+        }
+
         [DllImport("kernel32")]
         private static extern IntPtr LoadLibrary(string fileName);
 
         [DllImport("kernel32.dll")]
         private static extern IntPtr GetProcAddress(IntPtr handle, string procedureName);
+
+        [DllImport("kernel32")]
+        private static extern bool FreeLibrary(IntPtr handle);
     }
 
     [ExcludeFromCodeCoverage]
@@ -62,6 +72,11 @@ IntPtr ILibraryLoader.GetProcAddress(IntPtr dllHandle, string name)
             return result;
         }
 
+        void ILibraryLoader.UnloadLibrary(IntPtr handle)
+        {
+            dlclose(handle);
+        }
+
         [DllImport("libdl.so")]
         private static extern IntPtr dlopen(string fileName, int flags);
 
@@ -70,6 +85,9 @@ IntPtr ILibraryLoader.GetProcAddress(IntPtr dllHandle, string name)
 
         [DllImport("libdl.so")]
         private static extern IntPtr dlerror();
+
+        [DllImport("libdl.so")]
+        private static extern int dlclose(IntPtr handle);
     }
 
 
@@ -100,6 +118,11 @@ IntPtr ILibraryLoader.GetProcAddress(IntPtr dllHandle, string name)
             return result;
         }
 
+        void ILibraryLoader.UnloadLibrary(IntPtr handle)
+        {
+            dlclose(handle);
+        }
+
         [DllImport("dl")]
         private static extern IntPtr dlopen(string fileName, int flags);
 
@@ -108,6 +131,9 @@ IntPtr ILibraryLoader.GetProcAddress(IntPtr dllHandle, string name)
 
         [DllImport("dl")]
         private static extern IntPtr dlerror();
+
+        [DllImport("dl")]
+        private static extern int dlclose(IntPtr handle);
     }
 
 
@@ -138,6 +164,11 @@ IntPtr ILibraryLoader.GetProcAddress(IntPtr dllHandle, string name)
             return result;
         }
 
+        void ILibraryLoader.UnloadLibrary(IntPtr handle)
+        {
+            dlclose(handle);
+        }
+
         [DllImport("dl")]
         private static extern IntPtr dlopen(string fileName, int flags);
 
@@ -146,6 +177,9 @@ IntPtr ILibraryLoader.GetProcAddress(IntPtr dllHandle, string name)
 
         [DllImport("dl")]
         private static extern IntPtr dlerror();
+
+        [DllImport("dl")]
+        private static extern int dlclose(IntPtr handle);
     }
 
     [ExcludeFromCodeCoverage]
@@ -175,6 +209,11 @@ IntPtr ILibraryLoader.GetProcAddress(IntPtr dllHandle, string name)
             return result;
         }
 
+        void ILibraryLoader.UnloadLibrary(IntPtr handle)
+        {
+            dlclose(handle);
+        }
+
         [DllImport("libdl-2.20.so")]
         private static extern IntPtr dlopen(string fileName, int flags);
 
@@ -183,5 +222,8 @@ IntPtr ILibraryLoader.GetProcAddress(IntPtr dllHandle, string name)
 
         [DllImport("libdl-2.20.so")]
         private static extern IntPtr dlerror();
+
+        [DllImport("libdl-2.20.so")]
+        private static extern int dlclose(IntPtr handle);
     }
 }