@Override public void postProcess(IOTMessage ioTMessage) { switch (ioTMessage.getMessageType()) { case ConnectAcknowledgeMessage.MESSAGE_TYPE: ConnectAcknowledgeMessage conMessage = (ConnectAcknowledgeMessage) ioTMessage; /** Use the connection acknowledgement message to store session id for persistance. */ Channel channel = getChannel(ioTMessage.getConnectionId()); if (Objects.nonNull(channel)) { if (MqttConnectReturnCode.CONNECTION_ACCEPTED.equals(conMessage.getReturnCode())) { channel.attr(ServerImpl.REQUEST_SESSION_ID).set(ioTMessage.getSessionId()); } else { closeClient(ioTMessage.getConnectionId()); } } break; default: super.postProcess(ioTMessage); } }