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/WebSocketStream.cs

@@ -0,0 +1,91 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Threading;
+using Swan;
+
+namespace EmbedIO.WebSockets.Internal
+{
+    internal class WebSocketStream : MemoryStream
+    {
+        internal const int FragmentLength = 1016;
+
+        private readonly CompressionMethod _compression;
+        private readonly Opcode _opcode;
+
+        public WebSocketStream(byte[] data, Opcode opcode, CompressionMethod compression)
+            : base(data)
+        {
+            _compression = compression;
+            _opcode = opcode;
+        }
+
+        public IEnumerable<WebSocketFrame> GetFrames()
+        {
+            var compressed = _compression != CompressionMethod.None;
+            var stream = compressed
+                ? this.CompressAsync(_compression, true, CancellationToken.None).Await()
+                : this;
+
+            var len = stream.Length;
+
+            /* Not fragmented */
+
+            if (len == 0)
+            {
+                yield return new WebSocketFrame(Fin.Final, _opcode, Array.Empty<byte>(), compressed);
+                yield break;
+            }
+
+            var quo = len / FragmentLength;
+            var rem = (int)(len % FragmentLength);
+
+            byte[] buff;
+
+            if (quo == 0)
+            {
+                buff = new byte[rem];
+
+                if (stream.Read(buff, 0, rem) == rem)
+                    yield return new WebSocketFrame(Fin.Final, _opcode, buff, compressed);
+
+                yield break;
+            }
+
+            buff = new byte[FragmentLength];
+            if (quo == 1 && rem == 0)
+            {
+                if (stream.Read(buff, 0, FragmentLength) == FragmentLength)
+                    yield return new WebSocketFrame(Fin.Final, _opcode, buff, compressed);
+
+                yield break;
+            }
+
+            /* Send fragmented */
+
+            // Begin
+            if (stream.Read(buff, 0, FragmentLength) != FragmentLength)
+                yield break;
+
+            yield return new WebSocketFrame(Fin.More, _opcode, buff, compressed);
+
+            var n = rem == 0 ? quo - 2 : quo - 1;
+            for (var i = 0; i < n; i++)
+            {
+                if (stream.Read(buff, 0, FragmentLength) != FragmentLength)
+                    yield break;
+
+                yield return new WebSocketFrame(Fin.More, Opcode.Cont, buff, compressed);
+            }
+
+            // End
+            if (rem == 0)
+                rem = FragmentLength;
+            else
+                buff = new byte[rem];
+
+            if (stream.Read(buff, 0, rem) == rem)
+                yield return new WebSocketFrame(Fin.Final, Opcode.Cont, buff, compressed);
+        }
+    }
+}