Fix exceptions thrown when calling Shard.StopAsync (#82)

- DiscordClientWebSocket no longer erroneously sends a close acknowledgment when receiving a remote close after starting a close itself locally
- GatewaySocket no longer erroneously attempts to reconnect when receiving a remote close after starting a close itself locally

Author: Francessco121

src/Discore/Discore.csproj

@@ -3,9 +3,9 @@
   <PropertyGroup>
     <TargetFramework>netstandard1.5</TargetFramework>
     <Copyright>Ethan Lafrenais 2020</Copyright>
-    <Version>4.4.0</Version>
-    <AssemblyVersion>4.4.0.0</AssemblyVersion>
-    <FileVersion>4.4.0.0</FileVersion>
+    <Version>4.4.1</Version>
+    <AssemblyVersion>4.4.1.0</AssemblyVersion>
+    <FileVersion>4.4.1.0</FileVersion>
     <Authors>Ethan Lafrenais;Tristan Smith</Authors>
     <PackageTags>discord;discord-api;discord-library;dotnet-standard</PackageTags>
     <Description>Discore is a light-weight .NET Standard library designed for creating Discord bots.
@@ -16,7 +16,7 @@ Please note: Discore is not an official Discord API library!</Description>
     <RepositoryUrl>https://github.com/Francessco121/Discore.git</RepositoryUrl>
     <RepositoryType>git</RepositoryType>
     <PackageProjectUrl>https://github.com/Francessco121/Discore</PackageProjectUrl>
-    <PackageReleaseNotes>See https://github.com/Francessco121/Discore/releases/tag/v4.4.0</PackageReleaseNotes>
+    <PackageReleaseNotes>See https://github.com/Francessco121/Discore/releases/tag/v4.4.1</PackageReleaseNotes>
     <PackageLicenseFile></PackageLicenseFile>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
   </PropertyGroup>

src/Discore/WebSocket/Internal/DiscordClientWebSocket.cs

@@ -346,23 +346,32 @@ async Task ReceiveLoop()
                                 log.LogVerbose($"[ReceiveLoop] Received close: {result.CloseStatusDescription} " +
                                     $"{result.CloseStatus} ({(int)result.CloseStatus})");
 
-                                try
+                                if (socket.State == WebSocketState.Open 
+                                    || socket.State == WebSocketState.CloseReceived
+                                    || socket.State == WebSocketState.CloseSent)
                                 {
-                                    log.LogVerbose("[ReceiveLoop] Completing close handshake with status NormalClosure (1000)...");
+                                    try
+                                    {
+                                        log.LogVerbose("[ReceiveLoop] Completing close handshake with status NormalClosure (1000)...");
 
-                                    // Complete the closing handshake
-                                    await socket.CloseAsync(WebSocketCloseStatus.NormalClosure, "", abortCancellationSource.Token)
-                                        .ConfigureAwait(false);
+                                        // Complete the closing handshake
+                                        await socket.CloseAsync(WebSocketCloseStatus.NormalClosure, "", abortCancellationSource.Token)
+                                            .ConfigureAwait(false);
 
-                                    log.LogVerbose("[ReceiveLoop] Completed close handshake.");
-                                }
-                                catch (OperationCanceledException)
-                                {
-                                    log.LogVerbose($"[ReceiveLoop] Socket aborted while closing.");
+                                        log.LogVerbose("[ReceiveLoop] Completed close handshake.");
+                                    }
+                                    catch (OperationCanceledException)
+                                    {
+                                        log.LogVerbose($"[ReceiveLoop] Socket aborted while closing.");
+                                    }
+                                    catch (Exception ex)
+                                    {
+                                        log.LogError($"[ReceiveLoop] Failed to complete closing handshake: {ex}");
+                                    }
                                 }
-                                catch (Exception ex)
+                                else
                                 {
-                                    log.LogError($"[ReceiveLoop] Failed to complete closing handshake: {ex}");
+                                    log.LogVerbose("[ReceiveLoop] Close handshake completed by remote end.");
                                 }
 
                                 // Notify inheriting object

src/Discore/WebSocket/Internal/GatewaySocket.cs

@@ -48,6 +48,11 @@ partial class GatewaySocket : DiscordClientWebSocket
         /// </summary>
         bool receivedHello;
 
+        /// <summary>
+        /// Whether disconnection was initiated on our end.
+        /// </summary>
+        bool areWeDisconnecting;
+        
         bool isDisposed;
 
         DiscoreLogger log;
@@ -70,6 +75,8 @@ public GatewaySocket(string loggingName, int sequence,
         public override async Task DisconnectAsync(WebSocketCloseStatus closeStatus, string statusDescription, 
             CancellationToken cancellationToken)
         {
+            areWeDisconnecting = true;
+
             // Disconnect the socket
             await base.DisconnectAsync(closeStatus, statusDescription, cancellationToken)
                 .ConfigureAwait(false);
@@ -97,6 +104,10 @@ protected override async Task OnPayloadReceived(DiscordApiData payload)
 
         protected override void OnCloseReceived(WebSocketCloseStatus closeStatus, string closeDescription)
         {
+            // If we initiated a disconnect, this is just the remote end's acknowledgment
+            // and we should not start reconnecting
+            if (areWeDisconnecting) return;
+
             GatewayCloseCode code = (GatewayCloseCode)closeStatus;
             switch (code)
             {