UDP not send packet

Question

UDP not send packet

Avenitos opened this issue 5 years ago · comments

Hello!

sendUdp() function not send broadcast packets :(
in Wireshark no packets.

UIP library worked correctly!

#include <EtherCard.h>

const byte myMac[] PROGMEM = { 0x70, 0x69, 0x69, 0x2D, 0x30, 0x31 };
byte Ethernet::buffer[350];                          // Buffer must be 350 for DHCP to work

void setup() {
  Serial.begin(57600);
  Serial.println(F("\n[EtherCard UDP send]"));

  if (ether.begin(sizeof Ethernet::buffer, myMac, SS) == 0)
    Serial.println(F("Failed to access Ethernet controller"));

  static byte myip[] = { 172,16,1,147 };
  static byte gwip[] = { 172,16,1,1 };
  static byte dnsip[] = { 8,8,8,8 };
  static byte mask[] = { 255,255,255,0 };

  ether.staticSetup(myip, gwip, dnsip , mask);

  ether.printIp("IP:  ", ether.myip);
  ether.printIp("GW:  ", ether.gwip);
  ether.printIp("DNS: ", ether.dnsip);

  char payload[] = "My UDP message";
  uint8_t nSourcePort = 6454;
  uint8_t nDestinationPort = 6454;
  uint8_t broadcast[4] = { 255,255,255,255};
  
//ether.client_arp_whohas_blocking(ipDestinationAddress);
//delay(10);
//ether.sendUdp_mac(payload, sizeof(payload), nSourcePort, ipDestinationAddress, ether.returned_mac, nDestinationPort);

  ether.sendUdp(payload, sizeof(payload), nSourcePort, broadcast, nDestinationPort);

  Serial.println("UDP sent.");  
}

void loop() {
  ether.packetLoop(ether.packetReceive());
}

Avenitos · Answer 1 · Wed Jun 26 2019 05:42:37 GMT+0800 (China Standard Time)

I did not immediately understand why the ntp demo works, but sending to my local server does not work. It turns out that any sending within the local segment does not work, sending via the gateway to the Internet address works normally. Why is that?

Nicholas Humfrey · Answer 2 · Wed Jun 26 2019 06:15:29 GMT+0800 (China Standard Time)

It is probably something to do with the code that chooses the Layer 2 MAC address to send to.
When sending to the Internet, EtherCard just needs the use the routers MAC address. When sending to the local subnet, it needs to find and use the right address. Although for broadcast this should just be FF:FF:FF:FF:FF:FF.

Have you tried sending to your subnet's broadcast address ? 172.16.1.255?