Packet DecodePacketInternal(IByteBuffer buffer, int packetSignature, ref int remainingLength, IChannelHandlerContext context) { if (Signatures.IsPublish(packetSignature)) { var qualityOfService = (QualityOfService)((packetSignature >> 1) & 0x3); // take bits #1 and #2 ONLY and convert them into QoS value if (qualityOfService == QualityOfService.Reserved) { throw new DecoderException($"Unexpected QoS value of {(int)qualityOfService} for {PacketType.PUBLISH} packet."); } bool duplicate = (packetSignature & 0x8) == 0x8; // test bit#3 bool retain = (packetSignature & 0x1) != 0; // test bit#0 var packet = new PublishPacket(qualityOfService, duplicate, retain); DecodePublishPacket(buffer, packet, ref remainingLength); return(packet); } switch (packetSignature) // strict match checks for valid message type + correct values in flags part { case Signatures.PubAck: var pubAckPacket = new PubAckPacket(); DecodePacketIdVariableHeader(buffer, pubAckPacket, ref remainingLength); return(pubAckPacket); case Signatures.PubRec: var pubRecPacket = new PubRecPacket(); DecodePacketIdVariableHeader(buffer, pubRecPacket, ref remainingLength); return(pubRecPacket); case Signatures.PubRel: var pubRelPacket = new PubRelPacket(); DecodePacketIdVariableHeader(buffer, pubRelPacket, ref remainingLength); return(pubRelPacket); case Signatures.PubComp: var pubCompPacket = new PubCompPacket(); DecodePacketIdVariableHeader(buffer, pubCompPacket, ref remainingLength); return(pubCompPacket); case Signatures.PingReq: this.ValidateServerPacketExpected(packetSignature); return(PingReqPacket.Instance); case Signatures.Subscribe: this.ValidateServerPacketExpected(packetSignature); var subscribePacket = new SubscribePacket(); DecodePacketIdVariableHeader(buffer, subscribePacket, ref remainingLength); DecodeSubscribePayload(buffer, subscribePacket, ref remainingLength); return(subscribePacket); case Signatures.Unsubscribe: this.ValidateServerPacketExpected(packetSignature); var unsubscribePacket = new UnsubscribePacket(); DecodePacketIdVariableHeader(buffer, unsubscribePacket, ref remainingLength); DecodeUnsubscribePayload(buffer, unsubscribePacket, ref remainingLength); return(unsubscribePacket); case Signatures.Connect: this.ValidateServerPacketExpected(packetSignature); var connectPacket = new ConnectPacket(); DecodeConnectPacket(buffer, connectPacket, ref remainingLength, context); return(connectPacket); case Signatures.Disconnect: this.ValidateServerPacketExpected(packetSignature); return(DisconnectPacket.Instance); case Signatures.ConnAck: this.ValidateClientPacketExpected(packetSignature); var connAckPacket = new ConnAckPacket(); DecodeConnAckPacket(buffer, connAckPacket, ref remainingLength); return(connAckPacket); case Signatures.SubAck: this.ValidateClientPacketExpected(packetSignature); var subAckPacket = new SubAckPacket(); DecodePacketIdVariableHeader(buffer, subAckPacket, ref remainingLength); DecodeSubAckPayload(buffer, subAckPacket, ref remainingLength); return(subAckPacket); case Signatures.UnsubAck: this.ValidateClientPacketExpected(packetSignature); var unsubAckPacket = new UnsubAckPacket(); DecodePacketIdVariableHeader(buffer, unsubAckPacket, ref remainingLength); return(unsubAckPacket); case Signatures.PingResp: this.ValidateClientPacketExpected(packetSignature); return(PingRespPacket.Instance); default: throw new DecoderException($"First packet byte value of `{packetSignature}` is invalid."); } }