C++ EthernetUDP::read方法代码示例

time_t getNtpTime()
{
  while (Udp.parsePacket() > 0) ; // discard any previously received packets
  Serial.println("Transmit NTP Request");
  sendNTPpacket(ntp_server);
  uint32_t beginWait = millis();
  while (millis() - beginWait < 2000) {
    int size = Udp.parsePacket();
    if (size >= NTP_PACKET_SIZE) {
      Serial.println("Receive NTP Response");
      Udp.read(packetBuffer, NTP_PACKET_SIZE);  // read packet into the buffer
      unsigned long secsSince1900;
      unsigned long fracSecs;
      // convert four bytes starting at location 40 to a long integer
      secsSince1900 =  (unsigned long)packetBuffer[40] << 24;
      secsSince1900 |= (unsigned long)packetBuffer[41] << 16;
      secsSince1900 |= (unsigned long)packetBuffer[42] << 8;
      secsSince1900 |= (unsigned long)packetBuffer[43];
      fracSecs =  (unsigned long)packetBuffer[44] << 24;
      fracSecs |= (unsigned long)packetBuffer[45] << 16;
      fracSecs |= (unsigned long)packetBuffer[46] << 8;
      fracSecs |= (unsigned long)packetBuffer[47];
      return ((time_t)(secsSince1900 - 2208988800UL)<<32) + fracSecs;
    }
  }
  Serial.println("No NTP Response :-(");
  return 0; // return 0 if unable to get the time
}

int readUdp( char * buf, int size )
{
  if ( ! active ) return 0 ;
  int count = Udp.parsePacket() ;
  if ( count ) Udp.read( buf, size ) ;
  return count ;
}

void loop() {
  // if there's data available, read a packet
  int packetSize = Udp.parsePacket();
  char Size[4];
  if(packetSize)
  {
    if(packetSize == 4)
    {
      IPAddress remote = Udp.remoteIP();
    
      // read the packet into packetBufffer
      Udp.read(packetBuffer,UDP_TX_PACKET_MAX_SIZE);
      char Command[4];
      for(int nCom = 0; nCom < 4; nCom++)
        {
        Command[nCom] = packetBuffer[nCom];
        }
            
      if (Command[0] == 't')
      {
        digitalWrite(13, HIGH);
      }
      else if (Command[0] == 'r')
      {
        digitalWrite(12, HIGH);
      }
      else if (Command[0] == 'e')
      {
        digitalWrite(10, HIGH);
      }   
      else if (Command[0] == 'w')
      {
        analogWrite(11, 65);
      }      
      else
      {
        digitalWrite(13, LOW);
        digitalWrite(12, LOW);
        analogWrite(11, 0);
      }

      // send a reply, to the IP address and port that sent us the packet we received
      itoa(packetSize, Size, 10);
      Udp.beginPacket(Udp.remoteIP(), Udp.remotePort());
      Udp.write(ReplyBuffer);
      Udp.write(packetBuffer);
      Udp.write(Size);
      Udp.endPacket();
    delay(1000);
    }
    else
    {
      Udp.beginPacket(Udp.remoteIP(), Udp.remotePort());
      Udp.write("NOPE");
      Udp.endPacket();
    }
  }
}

// This function's purpose is to receive data and prepare it for parsing
void RobotOpenClass::handleData() {
	_packetBufferSize = Udp.parsePacket();
    
    // If there's data, read the packet in
    if (_packetBufferSize > 0) {
		_remotePort = Udp.remotePort();
		_remoteIp = Udp.remoteIP();
		Udp.read(_packetBufferAccessor, 256);
		parsePacket();	// Data is all set, time to parse through it
    }
}

/*
 * Send an NTP request to get the current time.
 *
 * This code was lifted from sample code that was part of an
 * arduino ntp libary.
 */
time_t parseNtpPacket() {
  
  Udp.read(packetBuffer,NTP_PACKET_SIZE);  // read the packet into the buffer

  unsigned long highWord = word(packetBuffer[40], packetBuffer[41]);
  unsigned long lowWord = word(packetBuffer[42], packetBuffer[43]);  

  unsigned long ntpTime = highWord << 16 | lowWord;  

  return (ntpTime - 2208988800UL);  // NTP time is based on 01-Jan-1900, but
									// we want Unix time which is seconds 
									// since 01-Jan-1970
  
}

void udpToUart()
{
  int packetSize = Udp.parsePacket();
  if(packetSize)
  {
    // read the packet into packetBufffer
    Udp.read(udpBuffer,MAX_HDLC_FRAME_SIZE);
    Serial.write(HDLC_SS_BYTE);
    Serial.write(udpBuffer, packetSize);
    Serial.write(0x12);
    Serial.write(0x34);
    Serial.write(HDLC_SS_BYTE);
  }
}

roveEthernet_Error roveEthernet_GetUdpMsg(roveIP* senderIP, void* buffer, size_t bufferSize)
{
  int packetSize = udpReceiver.parsePacket(); 
  
  if (packetSize > 0) //if there is a packet available
  {
    udpReceiver.read((char*)buffer, bufferSize);
    *senderIP = udpReceiver.remoteIP();
    return ROVE_ETHERNET_ERROR_SUCCESS;
  }
  else
  {
    return ROVE_ETHERNET_ERROR_WOULD_BLOCK;
  }
}

void UdpController::Loop()
{
    unsigned long currentMillis = millis();
    int packetSize = Udp.parsePacket();

    if (packetSize && packetSize == 3)
    {
        Udp.read(Buffer, UDP_TX_PACKET_MAX_SIZE);

        if (Buffer[0] == 0x28 && Buffer[1] == 0x06)
        {
            _traffic->SetMode((LightMode)Buffer[2]);
            _lastUpdateMillis = currentMillis;
        }
    }

    if ((currentMillis - _lastUpdateMillis) > UpdateIntervalMillis)
    {
        _traffic->ShowInconclusive();
    }
}

unsigned long getNtpTime()
{
  sendNTPpacket(timeServer); // send an NTP packet to a time server

    // wait to see if a reply is available
  delay(1000);  
  if ( Udp.parsePacket() ) {  
    // We've received a packet, read the data from it
    Udp.read(packetBuffer,NTP_PACKET_SIZE);  // read the packet into the buffer

    //the timestamp starts at byte 40 of the received packet and is four bytes,
    // or two words, long. First, esxtract the two words:

    unsigned long highWord = word(packetBuffer[40], packetBuffer[41]);
    unsigned long lowWord = word(packetBuffer[42], packetBuffer[43]);  
    // combine the four bytes (two words) into a long integer
    // this is NTP time (seconds since Jan 1 1900):
    unsigned long secsSince1900 = highWord << 16 | lowWord;  
    #ifdef LOGGING
    Serial.print("Seconds since Jan 1 1900 = " );
    Serial.println(secsSince1900);               
    #endif

    // now convert NTP time into everyday time:
    // Unix time starts on Jan 1 1970. In seconds, that's 2208988800:
    const unsigned long seventyYears = 2208988800UL;     
    // subtract seventy years:
    unsigned long epoch = secsSince1900 - seventyYears;  
    // print Unix time:
    #ifdef LOGGING
    Serial.print(UNIX_TIME);
    Serial.println(epoch);                               
    #endif
    return epoch;
  }
   
  return 0; // return 0 if unable to get the time
}

void commandInterfaceTick() {
  int packetSize = cmdsock.parsePacket();
  if(cmdsock.available()) {
    
    // read the packet into packetBufffer
    cmdsock.read(udpPacketBuffer, PACKET_SIZE);

    if(memcmp("INGV\0", udpPacketBuffer, 5) != 0) {
      return;
    }

    bool reboot = false;
    unsigned long unixTimeM = getUNIXTime();
    unsigned long uptime = getUNIXTime() - getBootTime();
    byte macaddress[6] = { 0 };
    getMACAddress(macaddress);
    uint32_t probeSpeed = getProbeSpeedStatistic();
    uint32_t freeramkb = freeMemory();
    float latency = 0;
    if(udpPacketBuffer[5] == PKTTYPE_GETINFO) {
      latency = tcpLatency();
    }

    float longitude = 0;
    float latitude = 0;

    switch(udpPacketBuffer[5]) {
      case PKTTYPE_DISCOVERY:
        // Reply to discovery
        udpPacketBuffer[5] = PKTTYPE_DISCOVERY_REPLY;

        memcpy(udpPacketBuffer + 6, macaddress, 6);
        
        memcpy(udpPacketBuffer + 12, getVersionAsString().c_str(), 4);
        memcpy(udpPacketBuffer + 16, "uno", 3);
        break;
      case PKYTYPE_PING:
        // Reply to ping
        udpPacketBuffer[5] = PKYTYPE_PONG;
        break;
      case PKTTYPE_SENDGPS:
        // Get coords
        udpPacketBuffer[5] = PKTTYPE_OK;

        memcpy(&latitude, udpPacketBuffer + 12, 4);
        memcpy(&longitude, udpPacketBuffer + 16, 4);
        reverse4bytes((byte*)&latitude);
        reverse4bytes((byte*)&longitude);
        
        break;
      case PKTTYPE_REBOOT:
        // Reboot
        // Reply with OK
        udpPacketBuffer[5] = PKTTYPE_OK;
        reboot = true;
        break;
      case PKTTYPE_GETINFO:
        udpPacketBuffer[5] = PKTTYPE_GETINFO_REPLY;

        memcpy(udpPacketBuffer + 6, macaddress, 6);
        memcpy(udpPacketBuffer + 28, &uptime, 4);
        memcpy(udpPacketBuffer + 32, &unixTimeM, 4);
        memcpy(udpPacketBuffer + 36, VERSION, 4);
        memcpy(udpPacketBuffer + 40, &freeramkb, 4);
        memcpy(udpPacketBuffer + 44, &latency, 4);
        memcpy(udpPacketBuffer + 53, "uno", 3);
        memcpy(udpPacketBuffer + 57, "MMA7361", 7);
        memcpy(udpPacketBuffer + 65, &probeSpeed, 4);

        break;
#ifdef RESET_ENABLED
      case PKTTYPE_RESET:
        initEEPROM();
        reboot = true;
        break;
#endif
      default:
        // Unknown packet or invalid command
        return;
    }

    if(longitude != 0 && latitude != 0) {
      setLongitude(longitude);
      setLatitude(latitude);
    }

    cmdsock.beginPacket(cmdsock.remoteIP(), cmdsock.remotePort());
    cmdsock.write(udpPacketBuffer, PACKET_SIZE);
    cmdsock.endPacket();
    cmdsock.flush();

    if(reboot) {
      soft_restart();
    }
  }
}

uint64_t getNTPtime()
{
    // send an NTP packet to a time server
    sendNTPpacket(timeServer);

    // wait to see if a reply is available
    delay(1000);
    if ( Udp.available() )
    {
        // read the packet into the buffer
        Udp.read(pb, NTP_PACKET_SIZE);      // New from IDE 1.0,

        // NTP contains four timestamps with an integer part and a fraction part
        // we only use the integer part here
        unsigned long t1, t2, t3, t4;
        t1 = t2 = t3 = t4 = 0;
        for (int i=0; i< 4; i++)
        {
            t1 = t1 << 8 | pb[16+i];
            t2 = t2 << 8 | pb[24+i];
            t3 = t3 << 8 | pb[32+i];
            t4 = t4 << 8 | pb[40+i];
        }

        // part of the fractional part
        // could be 4 bytes but this is more precise than the 1307 RTC
        // which has a precision of ONE second
        // in fact one byte is sufficient for 1307
        float f1,f2,f3,f4;
        f1 = ((long)pb[20] * 256 + pb[21]) / 65536.0;
        f2 = ((long)pb[28] * 256 + pb[29]) / 65536.0;
        f3 = ((long)pb[36] * 256 + pb[37]) / 65536.0;
        f4 = ((long)pb[44] * 256 + pb[45]) / 65536.0;

        // NOTE:
        // one could use the fractional part to set the RTC more precise
        // 1) at the right (calculated) moment to the NEXT second!
        //    t4++;
        //    delay(1000 - f4*1000);
        //    RTC.adjust(DateTime(t4));
        //    keep in mind that the time in the packet was the time at
        //    the NTP server at sending time so one should take into account
        //    the network latency (try ping!) and the processing of the data
        //    ==> delay (850 - f4*1000);
        // 2) simply use it to round up the second
        //    f > 0.5 => add 1 to the second before adjusting the RTC
        //   (or lower threshold eg 0.4 if one keeps network latency etc in mind)
        // 3) a SW RTC might be more precise, => ardomic clock :)


        // convert NTP to UNIX time, differs seventy years = 2208988800 seconds
        // NTP starts Jan 1, 1900
        // Unix time starts on Jan 1 1970.
        const unsigned long seventyYears = 2208988800UL;
        t1 -= seventyYears;
        t2 -= seventyYears;
        t3 -= seventyYears;
        t4 -= seventyYears;


        //Serial.println("T1 .. T4 && fractional parts");
        //PrintDateTime(DateTime(t1)); Serial.println(f1,4);
        //PrintDateTime(DateTime(t2)); Serial.println(f2,4);
        //PrintDateTime(DateTime(t3)); Serial.println(f3,4);

        //PrintDateTime(t4);
        char ntpTime[21];
        //GetDatetimeString(t4, ntpTime);
        Serial.println(f4,4);
        Serial.println();

        // Adjust timezone and DST... in my case substract 4 hours for Chile Time
        // or work in UTC?
        t4 -= (3 * 3600L);     // Notice the L for long calculations!!
        t4 += 1;               // adjust the delay(1000) at begin of loop!
        if (f4 > 0.4) t4++;    // adjust fractional part, see above
    }

    else
    {
        Serial.println("Failed to get NTP UDP packet!");
    }
}

bool gatewayTransportSend(MyMessage &message)
{
	bool ret = true;
	char *_ethernetMsg = protocolFormat(message);

    setIndication(INDICATION_GW_TX);

	_w5100_spi_en(true);
	#if defined(MY_CONTROLLER_IP_ADDRESS)
		#if defined(MY_USE_UDP)
			_ethernetServer.beginPacket(_ethernetControllerIP, MY_PORT);
			_ethernetServer.write(_ethernetMsg, strlen(_ethernetMsg));
			// returns 1 if the packet was sent successfully
			ret = _ethernetServer.endPacket();
		#else
			EthernetClient client;
			#if defined(MY_CONTROLLER_URL_ADDRESS)
	                	if (client.connected() || client.connect(MY_CONTROLLER_URL_ADDRESS, MY_PORT)) {
	        	#else
	                	if (client.connected() || client.connect(_ethernetControllerIP, MY_PORT)) {
	        	#endif
	                	client.write(_ethernetMsg, strlen(_ethernetMsg));
	                }
	                else {
	                	// connecting to the server failed!
	                	ret = false;
	                }
		#endif
	#else
		// Send message to connected clients
		#if defined(MY_GATEWAY_ESP8266)
			for (uint8_t i = 0; i < ARRAY_SIZE(clients); i++)
			{
				if (clients[i] && clients[i].connected())
				{
					clients[i].write((uint8_t*)_ethernetMsg, strlen(_ethernetMsg));
				}
			}
		#else
			_ethernetServer.write(_ethernetMsg);
		#endif
	#endif
	_w5100_spi_en(false);
	return ret;

}


#if defined(MY_GATEWAY_ESP8266)
	bool _readFromClient(uint8_t i) {
		while (clients[i].connected() && clients[i].available()) {
			char inChar = clients[i].read();
			if (inputString[i].idx < MY_GATEWAY_MAX_RECEIVE_LENGTH - 1) {
				// if newline then command is complete
				if (inChar == '\n' || inChar == '\r') {
					// Add string terminator and prepare for the next message
					inputString[i].string[inputString[i].idx] = 0;
					debug(PSTR("Client %d: %s\n"), i, inputString[i].string);
					inputString[i].idx = 0;
					if (protocolParse(_ethernetMsg, inputString[i].string)) {
						return true;
					}

				} else {
					// add it to the inputString:
					inputString[i].string[inputString[i].idx++] = inChar;
				}
			} else {
				// Incoming message too long. Throw away
				debug(PSTR("Client %d: Message too long\n"), i);
				inputString[i].idx = 0;
				// Finished with this client's message. Next loop() we'll see if there's more to read.
				break;
			}
		}
		return false;
	}
#else
	bool _readFromClient() {
		while (client.connected() && client.available()) {
			char inChar = client.read();
			if (inputString.idx < MY_GATEWAY_MAX_RECEIVE_LENGTH - 1) {
				// if newline then command is complete
				if (inChar == '\n' || inChar == '\r') {
					// Add string terminator and prepare for the next message
					inputString.string[inputString.idx] = 0;
					debug(PSTR("Eth: %s\n"), inputString.string);
					inputString.idx = 0;
					if (protocolParse(_ethernetMsg, inputString.string)) {
						return true;
					}

				} else {
					// add it to the inputString:
					inputString.string[inputString.idx++] = inChar;
				}
			} else {
				// Incoming message too long. Throw away
				debug(PSTR("Eth: Message too long\n"));
				inputString.idx = 0;
//.........这里部分代码省略.........

SNMP_API_STAT_CODES AgentuinoClass::requestPdu(SNMP_PDU *pdu)
{
	char *community;
	// sequence length
	byte seqLen;
	// version
	byte verLen, verEnd;
	// community string
	byte comLen, comEnd;
	// pdu
	byte pduTyp, pduLen;
	byte ridLen, ridEnd;
	byte errLen, errEnd;
	byte eriLen, eriEnd;
	byte vblTyp, vblLen;
	byte vbiTyp, vbiLen;
	byte obiLen, obiEnd;
	byte valTyp, valLen, valEnd;
	byte i;
	//
	// set packet packet size (skip UDP header)
	_packetSize = Udp.available();
	//
	// reset packet array
	memset(_packet, 0, SNMP_MAX_PACKET_LEN);
	//
	// validate packet
	if ( _packetSize != 0 && _packetSize > SNMP_MAX_PACKET_LEN ) {
		//
		//SNMP_FREE(_packet);

		return SNMP_API_STAT_PACKET_TOO_BIG;
	}
	//
	// get UDP packet
	//Udp.parsePacket();
	Udp.read(_packet, _packetSize);
// 	Udp.readPacket(_packet, _packetSize, _dstIp, &_dstPort);
	//
	// packet check 1
	if ( _packet[0] != 0x30 ) {
		//
		//SNMP_FREE(_packet);

		return SNMP_API_STAT_PACKET_INVALID;
	}
	//
	// sequence length
	seqLen = _packet[1];
	// version
	verLen = _packet[3];
	verEnd = 3 + verLen;
	// community string
	comLen = _packet[verEnd + 2];
	comEnd = verEnd + 2 + comLen;
	// pdu
	pduTyp = _packet[comEnd + 1];
	pduLen = _packet[comEnd + 2];
	ridLen = _packet[comEnd + 4];
	ridEnd = comEnd + 4 + ridLen;
	errLen = _packet[ridEnd + 2];
	errEnd = ridEnd + 2 + errLen;
	eriLen = _packet[errEnd + 2];
	eriEnd = errEnd + 2 + eriLen;
	vblTyp = _packet[eriEnd + 1];
	vblLen = _packet[eriEnd + 2];
	vbiTyp = _packet[eriEnd + 3];
	vbiLen = _packet[eriEnd + 4];
	obiLen = _packet[eriEnd + 6];
	obiEnd = eriEnd + obiLen + 6;
	valTyp = _packet[obiEnd + 1];
	valLen = _packet[obiEnd + 2];
	valEnd = obiEnd + 2 + valLen;
	//
	// extract version
	pdu->version = 0;
	for ( i = 0; i < verLen; i++ ) {
		pdu->version = (pdu->version << 8) | _packet[5 + i];
	}
	//
	// validate version
	//
	// pdu-type
	pdu->type = (SNMP_PDU_TYPES)pduTyp;
	_dstType = pdu->type;
	//
	// validate community size
	if ( comLen > SNMP_MAX_NAME_LEN ) {
		// set pdu error
		pdu->error = SNMP_ERR_TOO_BIG;
		//
		return SNMP_API_STAT_NAME_TOO_BIG;
	}
	//
	//
	// validate community name
	if ( pdu->type == SNMP_PDU_SET && comLen == _setSize ) {
		//
		for ( i = 0; i < _setSize; i++ ) {
			if( _packet[verEnd + 3 + i] != (byte)_setCommName[i] ) {
//.........这里部分代码省略.........

void loop() {

    if ((unsigned long) (millis() - previousEth) >= interval_ethernet) { //entra a cada 50ms
        previousEth = millis();
        if(count_eth == 0) { //espera completar um ciclo de todas as funções chamadas
            int packetSize = Udp.parsePacket();
            count_eth = 2;
            Serial.println("entrou eth");
            received = 0;
            if (packetSize) {
                set_debug(PC3);

#ifdef debug
                Serial.println("entrou eth RX ");
                Serial.print("Received packet of size ");
                Serial.println(packetSize);
                Serial.print("From ");
                IPAddress remote = Udp.remoteIP();
                for (int i =0; i < 4; i++)
                {
                    Serial.print(remote[i], DEC);
                    if (i < 3)
                    {
                        Serial.print(".");
                    }
                }
                Serial.print(", port ");
                Serial.println(Udp.remotePort());

                Serial.println("Contents:");
                Serial.println(packetBuffer);
#endif
                received = Udp.read();
                charBuffer.put(received);

#ifdef debug
                Serial.println("\rchar recebido:");
                Serial.write(received);
#endif

                /////////////////////////////
                clear_debug(PC3);
            }
        } else {
            count_eth--;
            Serial.println("entrou eth NADA");
            if (charBuffer.getSize() > 5) charBuffer.clear();
            if( charBuffer.getSize() > 0 )
                received = charBuffer.get();
            Serial.println("received:");
            Serial.println(received);

        }
    }
#ifdef debug
    Serial.println("client disconnected");
#endif
    /****************FIM ROTINA ETHERNET ***************************************************/


    if ((unsigned long) (millis() - previousADC) >= interval_adc) { //entra a cada 60ms
        previousADC = millis();
        set_debug(PC4);
        if (count_adc == 0) {
            count_adc = 1;
            /*testa obstaculo IR*/
            Serial.println("entrou adc OBSTACULO ");

            IR_obstaculo = 0;
            IR_obstaculo = verificaObstaculoIR();
#ifdef debug
            Serial.println("distancia_ir");
            Serial.println(IR_obstaculo);
            Serial.println("\r");
#endif
            if (IR_obstaculo > IR_OBSTACLE_THRESHOLD)
                obstacle_flag = 0;
            else if (IR_obstaculo > IR_OBSTACLE_THRESHOLD
                    && IR_obstaculo < IR_OBSTACLE_UPPER_THRESHOLD)
                obstacle_flag = 1;
            else if (IR_obstaculo <= IR_OBSTACLE_THRESHOLD)
                obstacle_flag = 2;
            clear_debug(PC4);
        } else {
            count_adc=0;
            Serial.println("entrou adc NADA ");

        }
    }

    /***************** FIM ROTINA ADC********************************/

    if ((unsigned long) (millis() - previousMotores) >= interval_motores) { //entra a cada 100ms
        previousMotores = millis();

        if (ciclosClock_motor == 2) { //duas bordas de subida depois de acionar o motor (200ms depois de acionar o motor)
            Serial.println("motor stop ");
            stopMove();
            ciclosClock_motor = 0;
        }
//.........这里部分代码省略.........

/**
   * Parses incoming SNMP messages.
   *
   * Original Auther: Rex Park
   * Updated: November 7, 2015 (Added support for Inform responses (SNMP_PDU_RESPONSE)
   */
SNMP_API_STAT_CODES SNMPClass::requestPdu(SNMP_PDU *pdu, char *extra_data, int extra_data_max_size)
{
  // sequence length
  uint16_t seqLen, valLen, vblLen, pduLen;
  // version
  byte verLen, verEnd;
  // community string
  byte comLen, comEnd;
  // pdu
  byte pduTyp, pduEnd;
  byte ridLen, ridEnd;
  byte errLen, errEnd;
  byte eriLen, eriEnd;
  byte vblTyp;
  byte vbiTyp, vbiLen;
  byte obiLen, obiEnd;
  byte valTyp, valEnd;
  int i;

  // set packet packet size (skip UDP header)
  _packetSize = Udp.available();
  _packetPos = 0;

  // reset packet array
  memset(_packet, 0, SNMP_MAX_PACKET_LEN);
  //
  // validate packet
  if ( _packetSize <= 0) {
    return SNMP_API_STAT_PACKET_TOO_BIG;
  }
  
  // get UDP packet
  if(_udp_extra_data_packet == true){

    if(extra_data != NULL){
      memset(extra_data, 0, extra_data_max_size);
    }
    
    Udp.read(_packet, _packetSize - extra_data_max_size);

    if(extra_data != NULL){
      Udp.read((byte*)extra_data, extra_data_max_size);
    }
  }else{
    Udp.read(_packet, _packetSize);
  }
  
//  Serial.println("Incomming: ");
//  for(int i = 0; i < _packetSize; i++){
//    Serial.print(_packet[i],HEX);
//    Serial.print(" ");
//  }
//  Serial.println();

  // packet check 1
  if ( _packet[0] != 0x30 ) {
    return SNMP_API_STAT_PACKET_INVALID;
  }
  

  // sequence length
  if(_packet[1] >= 0x82){
    seqLen = combine_msb_lsb(_packet[2], _packet[3]);
    _packetPos = 4;
  }
  else if(_packet[1] == 0x81){
    seqLen = _packet[2];
    _packetPos = 3;
  }else{
    seqLen = _packet[1];
    _packetPos = 2;
  }
  
  // version
  if(_packet[_packetPos] != 0x02){
    return SNMP_API_STAT_PACKET_INVALID;
  }
  
  verLen = _packet[_packetPos+1];//used to be hard coded as index 3
  verEnd = _packetPos+1 + verLen;
  
  // community string
  comLen = _packet[verEnd + 2];
  comEnd = verEnd + 2 + comLen;
  
  // pdu
  pduTyp = _packet[comEnd + 1];
  if(_packet[comEnd + 2] >= 0x82){
    pduLen = combine_msb_lsb(_packet[comEnd +3], _packet[comEnd +4]);
    pduEnd = comEnd + 2 + pduLen + 2;
    _packetPos = comEnd + 2 + 2;
  }
  else if(_packet[comEnd + 2] == 0x81){
    pduLen = _packet[comEnd +3];
//.........这里部分代码省略.........