All cancelTokens should be linked to the parent's. Always cache cancelTokens.

src/Discord.Net/DiscordClient.cs

@@ -75,8 +75,9 @@ namespace Discord
 		public Users Users => _users;
 		private readonly Users _users;
 
-		public CancellationToken CancelToken => _cancelToken.Token;
-		private CancellationTokenSource _cancelToken;
+		public CancellationToken CancelToken => _cancelToken;
+		private CancellationTokenSource _cancelTokenSource;
+		private CancellationToken _cancelToken;
 
 		/// <summary> Initializes a new instance of the DiscordClient class. </summary>
 		public DiscordClient(DiscordClientConfig config = null)
@@ -509,7 +510,7 @@ namespace Discord
 							if (_config.EnableVoice)
 							{
 								string host = "wss://" + data.Endpoint.Split(':')[0];
-                                await _voiceSocket.Login(host, data.GuildId, _currentUserId, _dataSocket.SessionId, data.Token).ConfigureAwait(false);
+                                await _voiceSocket.Login(host, data.GuildId, _currentUserId, _dataSocket.SessionId, data.Token, _cancelToken).ConfigureAwait(false);
 							}
 						}
 						break;
@@ -576,7 +577,8 @@ namespace Discord
             try
 			{
 				_disconnectedEvent.Reset();
-				_cancelToken = new CancellationTokenSource();
+				_cancelTokenSource = new CancellationTokenSource();
+				_cancelToken = _cancelTokenSource.Token;
 				_state = (int)DiscordClientState.Connecting;
 
 				_api.Token = token;
@@ -584,14 +586,14 @@ namespace Discord
 				if (_config.LogLevel >= LogMessageSeverity.Verbose)
 					RaiseOnLog(LogMessageSeverity.Verbose, LogMessageSource.Authentication, $"Websocket endpoint: {url}");
 				
-				await _dataSocket.Login(url, token).ConfigureAwait(false);				
+				await _dataSocket.Login(url, token, _cancelToken).ConfigureAwait(false);				
 
 				_runTask = RunTasks();
 
 				try
 				{
 					//Cancel if either Disconnect is called, data socket errors or timeout is reached
-					var cancelToken = CancellationTokenSource.CreateLinkedTokenSource(_cancelToken.Token, _dataSocket.CancelToken).Token;
+					var cancelToken = CancellationTokenSource.CreateLinkedTokenSource(_cancelToken, _dataSocket.CancelToken).Token;
                     if (!_connectedEvent.Wait(_config.ConnectionTimeout, cancelToken)) 
 						throw new Exception("Operation timed out.");
 				}
@@ -638,7 +640,7 @@ namespace Discord
 			{
 				_wasDisconnectUnexpected = isUnexpected;
 				_disconnectReason = ExceptionDispatchInfo.Capture(ex);
-				_cancelToken.Cancel();
+				_cancelTokenSource.Cancel();
 			}
 
 			if (!skipAwait)
@@ -730,7 +732,7 @@ namespace Discord
 		//Experimental
 		private Task MessageQueueLoop()
 		{
-			var cancelToken = _cancelToken.Token;
+			var cancelToken = _cancelToken;
 			int interval = _config.MessageQueueInterval;
 
 			return Task.Run(async () =>

src/Discord.Net/Net/WebSockets/DataWebSocket.cs

@@ -1,6 +1,7 @@
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
 using System;
+using System.Threading;
 using System.Threading.Tasks;
 
 namespace Discord.Net.WebSockets
@@ -18,9 +19,9 @@ namespace Discord.Net.WebSockets
 		{
 		}
 		
-		public async Task Login(string host, string token)
+		public async Task Login(string host, string token, CancellationToken cancelToken)
 		{
-			await base.Connect(host);
+			await base.Connect(host, cancelToken);
 			
 			Commands.Login msg = new Commands.Login();
 			msg.Payload.Token = token;

src/Discord.Net/Net/WebSockets/VoiceWebSocket.cs

@@ -52,14 +52,14 @@ namespace Discord.Net.WebSockets
 			_targetAudioBufferLength = client.Config.VoiceBufferLength / 20; //20 ms frames
 		}
 
-		public Task Login(string host, string serverId, string userId, string sessionId, string token)
+		public Task Login(string host, string serverId, string userId, string sessionId, string token, CancellationToken cancelToken)
 		{
 			_serverId = serverId;
 			_userId = userId;
 			_sessionId = sessionId;
 			_token = token;
 
-			return base.Connect(host);
+			return base.Connect(host, cancelToken);
 		}
 
 		protected override Task[] Run()
@@ -110,8 +110,7 @@ namespace Discord.Net.WebSockets
 
 		private async Task ReceiveVoiceAsync()
 		{
-			var cancelSource = _cancelToken;
-			var cancelToken = cancelSource.Token;
+			var cancelToken = _cancelToken;
 
 			await Task.Run(async () =>
 			{
@@ -145,8 +144,8 @@ namespace Discord.Net.WebSockets
 #else
 		private Task SendVoiceAsync()
 		{
-			var cancelSource = _cancelToken;
-			var cancelToken = cancelSource.Token;
+			var cancelToken = _cancelToken;
+
 			return Task.Run(async () =>
 			{
 #endif
@@ -239,7 +238,7 @@ namespace Discord.Net.WebSockets
 		//Closes the UDP socket when _disconnectToken is triggered, since UDPClient doesn't allow passing a canceltoken
 		private Task WatcherAsync()
 		{
-			var cancelToken = _cancelToken.Token;
+			var cancelToken = _cancelToken;
 			return cancelToken.Wait()
 				.ContinueWith(_ => _udp.Close());
 		}
@@ -387,7 +386,7 @@ namespace Discord.Net.WebSockets
 
 		public void SendPCMFrames(byte[] data, int bytes)
 		{
-			var cancelToken = _cancelToken.Token;
+			var cancelToken = _cancelToken;
 			if (!_isReady || cancelToken == null)
 				throw new InvalidOperationException("Not connected to a voice server.");
 			if (bytes == 0)
@@ -441,7 +440,7 @@ namespace Discord.Net.WebSockets
 					Buffer.BlockCopy(_encodingBuffer, 0, payload, 0, encodedLength);
 
 					//Wait until the queue has a spot open
-					_sendQueueWait.Wait(_cancelToken.Token);
+					_sendQueueWait.Wait(_cancelToken);
 					_sendQueue.Enqueue(payload);
 					if (_sendQueue.Count >= _targetAudioBufferLength)
 						_sendQueueWait.Reset();

src/Discord.Net/Net/WebSockets/WebSocket.cs

@@ -47,8 +47,9 @@ namespace Discord.Net.WebSockets
 		protected ExceptionDispatchInfo _disconnectReason;
 		private bool _wasDisconnectUnexpected;
 
-		public CancellationToken CancelToken => _cancelToken.Token;
-		protected CancellationTokenSource _cancelToken;
+		public CancellationToken CancelToken => _cancelToken;
+		private CancellationTokenSource _cancelTokenSource;
+		protected CancellationToken _cancelToken;
 
 		public WebSocket(DiscordClient client)
 		{
@@ -64,20 +65,18 @@ namespace Discord.Net.WebSockets
 			};
         }
 
-		protected virtual async Task Connect(string host)
+		protected virtual async Task Connect(string host, CancellationToken cancelToken)
 		{
-			if (_state != (int)WebSocketState.Disconnected)
-				throw new InvalidOperationException("Client is already connected or connecting to the server.");
-
 			try
 			{
 				await Disconnect().ConfigureAwait(false);
 				
 				_state = (int)WebSocketState.Connecting;
 
-				_cancelToken = new CancellationTokenSource();
+				_cancelTokenSource = new CancellationTokenSource();
+				_cancelToken = CancellationTokenSource.CreateLinkedTokenSource(_cancelTokenSource.Token, cancelToken).Token;
 
-				await _engine.Connect(host, _cancelToken.Token).ConfigureAwait(false);
+				await _engine.Connect(host, _cancelToken).ConfigureAwait(false);
 				_host = host;
 				_lastHeartbeat = DateTime.UtcNow;
 
@@ -94,8 +93,8 @@ namespace Discord.Net.WebSockets
 			_state = (int)WebSocketState.Connected;
 			RaiseConnected();
         }
-		public Task Reconnect()
-			=> Connect(_host);
+		/*public Task Reconnect(CancellationToken cancelToken)
+			=> Connect(_host, _cancelToken);*/
 
 		public Task Disconnect() => DisconnectInternal(new Exception("Disconnect was requested by user."), isUnexpected: false);
 		protected async Task DisconnectInternal(Exception ex, bool isUnexpected = true, bool skipAwait = false)
@@ -118,7 +117,7 @@ namespace Discord.Net.WebSockets
 			{
 				_wasDisconnectUnexpected = isUnexpected;
 				_disconnectReason = ExceptionDispatchInfo.Capture(ex);
-				_cancelToken.Cancel();
+				_cancelTokenSource.Cancel();
 			}
 
 			if (!skipAwait)
@@ -154,12 +153,16 @@ namespace Discord.Net.WebSockets
 		}
 		protected virtual Task[] Run()
 		{
-			var cancelToken = _cancelToken.Token;
+			var cancelToken = _cancelToken;
             return _engine.RunTasks(cancelToken)
 				.Concat(new Task[] { HeartbeatAsync(cancelToken) })
 				.ToArray();
 		}
-		protected virtual Task Cleanup() { return TaskHelper.CompletedTask; }
+		protected virtual Task Cleanup()
+		{
+			_cancelTokenSource = null;
+            return TaskHelper.CompletedTask;
+		}
 
 		protected abstract Task ProcessMessage(string json);
 		protected abstract object GetKeepAlive();