while (running) {
   try {
       // wait for an incoming connection
       // check interface state every 5sec
       selector.select(5000);
       Iterator<SelectionKey> selectedKeys = selector
                    .selectedKeys().iterator();
       netInterfaceUp = isNetInterfaceUp(netInterfaceUp);
       while (selectedKeys.hasNext()) {
           SelectionKey skey =selectedKeys.next();
           selectedKeys.remove();
           //selector选择器接收连接请求
           if (skey.isValid() &&skey.isAcceptable()) {
                 ((Controller)listener).handleNewConnection(
                               selector,serverSelectionKey);
           }
       }
   } catch (Exception e) {
         continue;
   }
}

for (OFMessage msg : msgs) {
   logger.trace("Message received: {}", msg);
   this.lastMsgReceivedTimeStamp = System.currentTimeMillis();
   OFType type = msg.getType();
   switch (type) {
   case HELLO:
       sendFeaturesRequest();
       break;
   case ECHO_REQUEST:
       OFEchoReply echoReply = (OFEchoReply) factory.getMessage(OFType.ECHO_REPLY);
       byte []payload = ((OFEchoRequest)msg).getPayload();
       if (payload != null && payload.length != 0 ) {
            // the response must have the samepayload as the request
            echoReply.setPayload(payload);
            echoReply.setLength((short)(echoReply.getLength() + payload.length) );
       }
       // respond immediately
       asyncSendNow(echoReply, msg.getXid());
       // send features request if not sent yet
       sendFeaturesRequest();
       break;
   case ECHO_REPLY:
       this.probeSent = false;
       break;
   case FEATURES_REPLY:
       processFeaturesReply((OFFeaturesReply) msg);
       break;
   case GET_CONFIG_REPLY:
       // make sure that the switch can send the whole packet to the
       // controller
       if (((OFGetConfigReply) msg).getMissSendLength() == (short) 0xffff) {
            this.state = SwitchState.OPERATIONAL;
       }
       break;
   case BARRIER_REPLY:
       processBarrierReply((OFBarrierReply) msg);
       break;
   case ERROR:
       processErrorReply((OFError) msg);
       break;
   case PORT_STATUS:
       processPortStatusMsg((OFPortStatus) msg);
       break;
   case STATS_REPLY:
       processStatsReply((OFStatisticsReply) msg);
       break;
   case PACKET_IN:
       break;
   default:
       break;
   } // end of switch
   if (isOperational()) {
       ((Controller) core).takeSwitchEventMsg(thisISwitch, msg);
   }
} // end of for

case SWITCH_MESSAGE:
OFMessage msg = ev.getMsg();
if (msg != null) {
IMessageListener listener =messageListeners
.get(msg.getType());
if (listener != null) {
listener.receive(sw, msg);
}
}
break;

public PacketResultreceiveDataPacket(RawPacket inPkt) {
   if (inPkt == null) {
       logger.debug("Ignoring null packet");
       return PacketResult.IGNORED;
   }
   byte[] data = inPkt.getPacketData();
   if (data.length <= 0) {
       logger.trace("Ignoring zero length packet");
       return PacketResult.IGNORED;
   }
   if (!inPkt.getEncap().equals(LinkEncap.ETHERNET)) {
       logger.trace("Ignoring non ethernet packet");
       return PacketResult.IGNORED;
   }
   NodeConnector nodeConnector = inPkt.getIncomingNodeConnector();
   if (((Short)nodeConnector.getID()).equals(NodeConnector.SPECIALNODECONNECTORID)) {
       logger.trace("Ignoring ethernet packet received on special port:"
                +inPkt.getIncomingNodeConnector().toString());
       return PacketResult.IGNORED;
    }
   if (!connectionOutService.isLocal(nodeConnector.getNode())) {
       logger.debug("Discoery packets will not be processed from {} in anon-master controller", nodeConnector.toString());
       return PacketResult.IGNORED;
   }
   Ethernet ethPkt = new Ethernet();
   try {
       ethPkt.deserialize(data, 0, data.length * NetUtils.NumBitsInAByte);
   } catch (Exception e) {
       logger.warn("Failed to decode LLDP packet from {}: {}",inPkt.getIncomingNodeConnector(), e);
       return PacketResult.IGNORED;
   }
   if (ethPkt.getPayload() instanceof LLDP) {
       NodeConnector dst = inPkt.getIncomingNodeConnector();
       if (isEnabled(dst)) {
            if (!processDiscoveryPacket(dst,ethPkt)) {
                // Snoop the discovery pkt ifnot generated from us
                snoopDiscoveryPacket(dst,ethPkt);
            }
            return PacketResult.CONSUME;
       }
   }
   return PacketResult.IGNORED;
}