[C#] bug-fix for publish in websockets (#649)

* Sending publish with websocket headers for websocket server session
* Handling clean disconnection
* Fixed a nit for large images transfer that was causing problems
* simplified code a bit and fixed a nit

Co-authored-by: Rohan Kadekodi <kadekodirohan@gmail.com>

cs/remote/src/FASTER.server/WebsocketServerSession.cs

@@ -275,33 +275,28 @@ private unsafe bool ProcessBatch(byte[] buf, int offset)
                     }
 
                     var nextBufOffset = offset;
+                    nextBufOffset += msglen;
 
                     while (fin == false)
                     {
-                        nextBufOffset += msglen;
-
-                        fin = ((buf[nextBufOffset]) & 0b10000000) != 0;
+                        fin = (buf[nextBufOffset] & 0b10000000) != 0;
 
                         nextBufOffset++;
-                        var nextMsgLen = buf[nextBufOffset] - 128; // & 0111 1111
+                        int nextMsgLen = buf[nextBufOffset] & 0b01111111; // & 0111 1111
 
-                        offset++;
                         nextBufOffset++;
 
                         if (nextMsgLen < 125)
                         {
                             nextBufOffset++;
-                            offset++;
                         }
                         else if (nextMsgLen == 126)
                         {
-                            offset += 3;
                             nextMsgLen = BitConverter.ToUInt16(new byte[] { buf[nextBufOffset + 1], buf[nextBufOffset] }, 0);
                             nextBufOffset += 2;
                         }
                         else if (nextMsgLen == 127)
                         {
-                            offset += 9;
                             nextMsgLen = (int)BitConverter.ToUInt64(new byte[] { buf[nextBufOffset + 7], buf[nextBufOffset + 6], buf[nextBufOffset + 5], buf[nextBufOffset + 4], buf[nextBufOffset + 3], buf[nextBufOffset + 2], buf[nextBufOffset + 1], buf[nextBufOffset] }, 0);
                             nextBufOffset += 8;
                         }
@@ -311,10 +306,18 @@ private unsafe bool ProcessBatch(byte[] buf, int offset)
                         nextDecoderInfo.maskStart = nextBufOffset;
                         nextDecoderInfo.dataStart = nextBufOffset + 4;
                         decoderInfoList.Add(nextDecoderInfo);
-                        totalMsgLen += nextMsgLen;
-                        offset += 4;
+                        totalMsgLen += nextMsgLen; // Message length without the mask
+                        nextBufOffset += 4; // 4 bytes of masking
+                        nextBufOffset += nextMsgLen; // remaining message length
+                    }
+
+                    if (msglen == 2)
+                    {
+                        this.Dispose();
+                        return false;
                     }
 
+                    offset = nextBufOffset;
                     completeWSCommand = true;
 
                     var decodedIndex = 0;
@@ -330,7 +333,7 @@ private unsafe bool ProcessBatch(byte[] buf, int offset)
                         }
                     }
 
-                    offset += totalMsgLen;
+                    //offset += totalMsgLen;
                     readHead = offset;
                 }
 
@@ -575,7 +578,7 @@ private unsafe void Publish(ref byte* keyPtr, int keyLength, ref byte* valPtr, r
 
             byte* d = respObj.bufferPtr;
             var dend = d + respObj.buffer.Length;
-            var dcurr = d + sizeof(int); // reserve space for size
+            var dcurr = d + 10 + sizeof(int); // reserve space for websocket header and size
             byte* outputDcurr;
 
             dcurr += BatchHeader.Size;
@@ -613,15 +616,18 @@ private unsafe void Publish(ref byte* keyPtr, int keyLength, ref byte* valPtr, r
             }
 
             // Send replies
-            var dstart = d + sizeof(int);
+            var dtemp = d + 10;
+            var dstart = dtemp + sizeof(int);
             Unsafe.AsRef<BatchHeader>(dstart).NumMessages = 1;
             Unsafe.AsRef<BatchHeader>(dstart).SeqNo = 0;
-            int payloadSize = (int)(dcurr - d);
-            // Set packet size in header
-            *(int*)respObj.bufferPtr = -(payloadSize - sizeof(int));
+            int packetLen = (int)((dcurr - 10) - d);
+
+            CreateSendPacketHeader(ref d, packetLen);
+
+            *(int*)dtemp = (packetLen - sizeof(int));
             try
             {
-                messageManager.Send(socket, respObj, 0, payloadSize);
+                messageManager.Send(socket, respObj, (int)(d - respObj.bufferPtr), (int)(dcurr - d));
             }
             catch
             {