SNMP Trap Messages (Arduino with Ethernet Shield)

Projects Networking, Protocols, and Devices
1

Hi ppl,

does anyone knows how to receive a SNMP Trap in Arduino? And if possible show it in Serial Monitor?

In the attachment there is a Wireshark capture of an SNMP Trap message.

Thanks!

SNMP Trap.png
SNMP Trap.png1366×768 137 KB

2

Take a look at the UdpSendReceiveString example of the Ethernet library. It should give you enough hints of how to use the UDP feature to be able to parse the trap messages yourself.

3

Hi pylon,

I've already tried it. Unfortunately it didn't work, see the attachment: in the contents is just showed 2 characters, like an error.. (that characters differ if I customize my trap).

Maybe a simple PDU Ethernet Frame is a little bit different of a PDU Frame with SNMP Protocol included... I don't know..

If somebody can help.. I would appreciate.

Thanks,
Fred

serial monitor.png
serial monitor.png409×528 25.2 KB

4

Maybe you should post the code that you are using in that last serial monitor output.

5

Hi SurferTim,

the code is the same in sketch UDPSendReceiveString.pde available in Ethernet Library, I've just change the IP Address and local port. You have it below in this post.

You also have in the attachments:

  • where I generate the trap (MIB Browser Software: Trap with 1 binding saying Congratulations)
  • the result in Serial Monitor with the Content: "08"
  • the result in Wireshark: as you can see the "08" bytes belongs to the Header of SNMP and I want to get the data from the binding, "Congratulations"..

Maybe I have to do some changes in the EthernetUDP library but I don't know what yet... :confused:

Thanks for the answer!
Best Regards,
Fred

#include <SPI.h> // needed for Arduino versions later than 0018
#include <Ethernet.h>
#include <EthernetUdp.h> // UDP library from: bjoern@cs.stanford.edu 12/30/2008

// Enter a MAC address and IP address for your controller below.
// The IP address will be dependent on your local network:
byte mac[] = {
0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
IPAddress ip(192, 168, 99, 2);

unsigned int localPort = 162; // local port to listen on

// buffers for receiving and sending data
char packetBuffer[UDP_TX_PACKET_MAX_SIZE]; //buffer to hold incoming packet,
char ReplyBuffer[] = "acknowledged"; // a string to send back

// An EthernetUDP instance to let us send and receive packets over UDP
EthernetUDP Udp;

void setup() {
// start the Ethernet and UDP:
Ethernet.begin(mac,ip);
Udp.begin(localPort);

Serial.begin(9600);
}

void loop() {
// if there's data available, read a packet
int packetSize = Udp.parsePacket();
if(packetSize)
{
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*, DEC);*

6

I changed a few things in your code.

I increased the packetBuffer array size to 128 to hold a bigger packet.

I changed the way it prints the contents of the packet. It should print the entire contents of the packet in hex. The way you had it coded before would only print until it reached a zero byte. That is why it would not print the entire contents.

I apologize in advance for any typos.

#include <SPI.h>         // needed for Arduino versions later than 0018
#include <Ethernet.h>
#include <EthernetUdp.h>         // UDP library from: bjoern@cs.stanford.edu 12/30/2008


// Enter a MAC address and IP address for your controller below.
// The IP address will be dependent on your local network:
byte mac[] = {  
  0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
IPAddress ip(192, 168, 99, 2);

unsigned int localPort = 162;      // local port to listen on

// buffers for receiving and sending data
char packetBuffer[128]; //buffer to hold incoming packet,
char  ReplyBuffer[] = "acknowledged";       // a string to send back

// An EthernetUDP instance to let us send and receive packets over UDP
EthernetUDP Udp;

void setup() {
  // start the Ethernet and UDP:
  Ethernet.begin(mac,ip);
  Udp.begin(localPort);

  Serial.begin(9600);
}

void loop() {
  // if there's data available, read a packet
  int packetSize = Udp.parsePacket();
  if(packetSize)
  {
    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, DEC);
      if (i < 3)
      {
        Serial.print(".");
      }
    }
    Serial.print(", port ");
    Serial.println(Udp.remotePort());

    // read the packet into packetBufffer
    Udp.read(packetBuffer,127);

    if(packetSize > 127) packetSize = 127;

    Serial.println("Contents: ");

    for(int x = 0; x < packetSize;x++) {
        if(x%16 == 0) Serial.println();
        Serial.print(packetBuffer[x],HEX);
        Serial.print(" ");
    }

    // send a reply, to the IP address and port that sent us the packet we received
    Udp.beginPacket(Udp.remoteIP(), Udp.remotePort());
    Udp.write(ReplyBuffer);
    Udp.endPacket();
  }
  delay(10);
}
7

Hey SurferTim,

very helpful! Thanks a lot for your help and for your time!

I've just run it and works fine, know I will try to understand it :wink:

Thanks again!

8

Do a Google search for "SNMP protocol packet". The images are helpful in visualizing the packet structure.

9

Hi all!
Does anybody try to send SNMP trap from arduino?

10

Good day, a few years ago y modified the Agentuino library to be able to send SNMP (v1) traps, back then i posted it in this link: Agentuino - A lightweight SNMP Agent - Libraries - Arduino Forum

11

Hi,

I am using your Agentuino h and cpp file with the following code but I am not receiving any traps.

Could you please give this a quick lock over or if possible just send me what you have that works then hopefully I can figure it out.

Thanks,

Paul

SnmpArduino_2_12_2019R3.ino (12.9 KB)

12

I have the same problem, any persona have a solution to the trap send??

13

Hello, I am trying to send SNMP trap message through the arduino board, but I am unable to understand how to send it. I am using ethernet shield and PowerSNMP software to monitor the parameters. I am sharing the code here. Can anyone help me here?

Digital_out.ino (24.5 KB)