diff --git a/src/Microsoft.Net.WebSockets/CommonWebSocket.cs b/src/Microsoft.Net.WebSockets/CommonWebSocket.cs
index cae096cc94..b5fceae352 100644
--- a/src/Microsoft.Net.WebSockets/CommonWebSocket.cs
+++ b/src/Microsoft.Net.WebSockets/CommonWebSocket.cs
@@ -33,18 +33,28 @@ namespace Microsoft.Net.WebSockets
         private FrameHeader _frameInProgress;
         private long _frameBytesRemaining = 0;
 
-        public CommonWebSocket(Stream stream, string subProtocol, int receiveBufferSize)
+        public CommonWebSocket(Stream stream, string subProtocol, int receiveBufferSize, bool maskOutput, bool useZeroMask, bool unmaskInput)
         {
             _stream = stream;
             _subProtocl = subProtocol;
             _state = WebSocketState.Open;
             _receiveBuffer = new byte[receiveBufferSize];
-            _maskOutput = true; // TODO: client only.
-            _useZeroMask = false; // TODO: make optional
-            _unmaskInput = false; // TODO: server only
+            _maskOutput = maskOutput;
+            _useZeroMask = useZeroMask;
+            _unmaskInput = unmaskInput;
             _writeLock = new SemaphoreSlim(1);
         }
 
+        public static CommonWebSocket CreateClientWebSocket(Stream stream, string subProtocol, int receiveBufferSize, bool useZeroMask)
+        {
+            return new CommonWebSocket(stream, subProtocol, receiveBufferSize, maskOutput: true, useZeroMask: useZeroMask, unmaskInput: false);
+        }
+
+        public static CommonWebSocket CreateServerWebSocket(Stream stream, string subProtocol, int receiveBufferSize)
+        {
+            return new CommonWebSocket(stream, subProtocol, receiveBufferSize, maskOutput: false, useZeroMask: false, unmaskInput: true);
+        }
+
         public override WebSocketCloseStatus? CloseStatus
         {
             get { return _closeStatus; }
@@ -149,6 +159,11 @@ namespace Microsoft.Net.WebSockets
                 _receiveCount -= frameHeaderSize;
                 _frameBytesRemaining = _frameInProgress.DataLength;
 
+                if (_unmaskInput != _frameInProgress.Masked)
+                {
+                    throw new InvalidOperationException("Unmasking settings out of sync with data.");
+                }
+
                 // Ping or Pong frames
                 if (_frameInProgress.OpCode == Constants.OpCodes.PingFrame || _frameInProgress.OpCode == Constants.OpCodes.PongFrame)
                 {
@@ -171,13 +186,26 @@ namespace Microsoft.Net.WebSockets
 
             if (_frameInProgress.OpCode == Constants.OpCodes.CloseFrame)
             {
-                // TOOD: This assumes the close message fits in the buffer.
-                // TODO: Assert at least two bytes remaining for the close status code.
+                // The close message should be less than 125 bytes and fit in the buffer.
                 await EnsureDataAvailableOrReadAsync((int)_frameBytesRemaining, CancellationToken.None);
-                // TODO: Unmask (server only)
-                // TODO: Throw if the client detects an incoming masked frame.
-                _closeStatus = (WebSocketCloseStatus)((_receiveBuffer[_receiveOffset] << 8) | _receiveBuffer[_receiveOffset + 1]);
-                _closeStatusDescription = Encoding.UTF8.GetString(_receiveBuffer, _receiveOffset + 2, _receiveCount - 2) ?? string.Empty;
+
+                // Status code and message are optional
+                if (_frameBytesRemaining >= 2)
+                {
+                    ArraySegment<byte> dataSegment = new ArraySegment<byte>(_receiveBuffer, _receiveOffset + 2, (int)_frameBytesRemaining - 2);
+                    if (_unmaskInput)
+                    {
+                        // In place
+                        Utilities.Mask(_frameInProgress.MaskKey, dataSegment);
+                    }
+                    _closeStatus = (WebSocketCloseStatus)((_receiveBuffer[_receiveOffset] << 8) | _receiveBuffer[_receiveOffset + 1]);
+                    _closeStatusDescription = Encoding.UTF8.GetString(dataSegment.Array, dataSegment.Offset, dataSegment.Count) ?? string.Empty;
+                }
+                else
+                {
+                    _closeStatus = _closeStatus ?? WebSocketCloseStatus.NormalClosure;
+                    _closeStatusDescription = _closeStatusDescription ?? string.Empty;
+                }
                 result = new WebSocketReceiveResult(0, WebSocketMessageType.Close, true, (WebSocketCloseStatus)_closeStatus, _closeStatusDescription);
 
                 if (State == WebSocketState.Open)
@@ -192,49 +220,44 @@ namespace Microsoft.Net.WebSockets
                 return result;
             }
 
-            // Make sure there's at least some data in the buffer
-            if (_frameBytesRemaining > 0)
-            {
-                await EnsureDataAvailableOrReadAsync(1, cancellationToken);
-            }
-
-            // Copy buffered data to the users buffer
-            int bytesToRead = (int)Math.Min((long)buffer.Count, _frameBytesRemaining);
-            if (_receiveCount > 0)
-            {
-                // TODO: Unmask
-                int bytesToCopy = Math.Min(bytesToRead, _receiveCount);
-                Array.Copy(_receiveBuffer, _receiveOffset, buffer.Array, buffer.Offset, bytesToCopy);
-                if (bytesToCopy == _frameBytesRemaining)
-                {
-                    result = new WebSocketReceiveResult(bytesToCopy, GetMessageType(_frameInProgress.OpCode), _frameInProgress.Fin);
-                    _frameInProgress = null;
-                }
-                else
-                {
-                    result = new WebSocketReceiveResult(bytesToCopy, GetMessageType(_frameInProgress.OpCode), false);
-                }
-                _frameBytesRemaining -= bytesToCopy;
-                _receiveCount -= bytesToCopy;
-                _receiveOffset += bytesToCopy;
-            }
-            else
+            if (_frameBytesRemaining == 0)
             {
                 // End of an empty frame?
                 result = new WebSocketReceiveResult(0, GetMessageType(_frameInProgress.OpCode), true);
+                _frameInProgress = null;
+                return result;
             }
 
+            // Make sure there's at least some data in the buffer
+            await EnsureDataAvailableOrReadAsync(1, cancellationToken);
+            // Copy buffered data to the users buffer
+            int bytesToRead = (int)Math.Min((long)buffer.Count, _frameBytesRemaining);
+            int bytesToCopy = Math.Min(bytesToRead, _receiveCount);
+            Array.Copy(_receiveBuffer, _receiveOffset, buffer.Array, buffer.Offset, bytesToCopy);
+            if (_unmaskInput)
+            {
+                // TODO: mask alignment may be off between reads.
+                Utilities.Mask(_frameInProgress.MaskKey, new ArraySegment<byte>(buffer.Array, buffer.Offset, bytesToCopy));
+            }
+            if (bytesToCopy == _frameBytesRemaining)
+            {
+                result = new WebSocketReceiveResult(bytesToCopy, GetMessageType(_frameInProgress.OpCode), _frameInProgress.Fin);
+                _frameInProgress = null;
+            }
+            else
+            {
+                result = new WebSocketReceiveResult(bytesToCopy, GetMessageType(_frameInProgress.OpCode), false);
+            }
+            _frameBytesRemaining -= bytesToCopy;
+            _receiveCount -= bytesToCopy;
+            _receiveOffset += bytesToCopy;
+
             return result;
         }
 
         // We received a ping, send a pong in reply
         private async Task SendPongReply(CancellationToken cancellationToken)
         {
-            // TODO: Unmask data
-            if (_unmaskInput != _frameInProgress.Masked)
-            {
-                throw new InvalidOperationException("Unmasking settings out of sync with data.");
-            }
             ArraySegment<byte> dataSegment = new ArraySegment<byte>(_receiveBuffer, _receiveOffset, (int)_frameBytesRemaining);
             if (_unmaskInput)
             {
@@ -359,8 +382,13 @@ namespace Microsoft.Net.WebSockets
             fullData[1] = (byte)closeStatus;
             Array.Copy(descriptionBytes, 0, fullData, 2, descriptionBytes.Length);
 
-            // TODO: Masking
-            FrameHeader frameHeader = new FrameHeader(true, Constants.OpCodes.CloseFrame, true, 0, fullData.Length);
+            int mask = GetNextMask();
+            if (_maskOutput)
+            {
+                Utilities.Mask(mask, new ArraySegment<byte>(fullData));
+            }
+
+            FrameHeader frameHeader = new FrameHeader(true, Constants.OpCodes.CloseFrame, _maskOutput, mask, fullData.Length);
             ArraySegment<byte> segment = frameHeader.Buffer;
             await _stream.WriteAsync(segment.Array, segment.Offset, segment.Count, cancellationToken);
             await _stream.WriteAsync(fullData, 0, fullData.Length, cancellationToken);
diff --git a/src/Microsoft.Net.WebSockets/WebSocketClient.cs b/src/Microsoft.Net.WebSockets/WebSocketClient.cs
index 1a32277d8f..a78b2f5e17 100644
--- a/src/Microsoft.Net.WebSockets/WebSocketClient.cs
+++ b/src/Microsoft.Net.WebSockets/WebSocketClient.cs
@@ -49,7 +49,7 @@ namespace Microsoft.Net.WebSockets.Client
             Stream stream = response.GetResponseStream();
             // Console.WriteLine(stream.CanWrite + " " + stream.CanRead);
 
-            return new CommonWebSocket(stream, null, ReceiveBufferSize);
+            return CommonWebSocket.CreateClientWebSocket(stream, null, ReceiveBufferSize, useZeroMask: false);
         }
     }
 }