Got at least one data fetching method working; turns out, we can't use a patched LogicStack to get the data

Vendor/EmbedIO-3.5.2/WebSockets/Internal/Mask.cs

@@ -0,0 +1,22 @@
+namespace EmbedIO.WebSockets.Internal
+{
+    /// <summary>
+    /// Indicates whether the payload data of a WebSocket frame is masked.
+    /// </summary>
+    /// <remarks>
+    /// The values of this enumeration are defined in
+    /// <see href="http://tools.ietf.org/html/rfc6455#section-5.2">Section 5.2</see> of RFC 6455.
+    /// </remarks>
+    internal enum Mask : byte
+    {
+        /// <summary>
+        /// Equivalent to numeric value 0. Indicates not masked.
+        /// </summary>
+        Off = 0x0,
+
+        /// <summary>
+        /// Equivalent to numeric value 1. Indicates masked.
+        /// </summary>
+        On = 0x1,
+    }
+}