Simple SNMP Example

Overview

This example demonstrates how to implement SNMP (Simple Network Management Protocol) functionality on a NetBurner device. SNMP is a standard protocol for monitoring and managing network devices. This example shows how to:

Enable and initialize the SNMP agent
Configure system description and enterprise OID
Send SNMP traps with custom variable bindings
Integrate SNMP with a command processor for interactive control

Features

SNMP agent with configurable system description
Enterprise-specific trap generation with custom data
Telnet command interface (port 23) for SNMP operations
Serial console command interface
User authentication for command sessions
HTTP web server for device access

How It Works

+-------------------+       +------------------+       +------------------+
|   SNMP Manager    |       |  NetBurner       |       |  Serial Console  |
|   (Network)       |       |  SNMP Agent      |       |  or Telnet       |
+-------------------+       +------------------+       +------------------+
         |                         |                          |
         |   SNMP Get/Set          |                          |
         | <---------------------> |                          |
         |                         |                          |
         |   SNMP Trap             |      'T' Command         |
         | <---------------------- | <----------------------- |
         |                         |                          |
         |                         |      'D' Command         |
         |                         | <----------------------- |
         |                         |          |               |
         |                         |          v               |
         |                         |   Dump SNMP Tree         |
         |                         |          |               |
         |                         |          v               |
         |                         | -----------------------> |
         |                         |   (Tree Output)          |
+-------------------+       +------------------+       +------------------+

Application Architecture

+------------------------------------------------------------------+
|                         UserMain()                                |
+------------------------------------------------------------------+
           |                    |                    |
           v                    v                    v
+------------------+  +------------------+  +------------------+
|   init()         |  |   StartHttp()    |  | SNMP Agent       |
|   Network Stack  |  |   Web Server     |  | (SnmpServlet)    |
+------------------+  +------------------+  +------------------+
                               |
                               v
                      +------------------+
                      | Command          |
                      | Processor        |
                      | (Port 23/Serial) |
                      +------------------+
                               |
           +-------------------+-------------------+
           |                   |                   |
           v                   v                   v
+------------------+  +------------------+  +------------------+
| ProcessAuth()    |  | ProcessCommand() |  | ProcessConnect() |
| Authentication   |  | D: Dump Tree     |  | Session Setup    |
|                  |  | T: Send Trap     |  |                  |
+------------------+  +------------------+  +------------------+

SNMP Trap Flow

When a user sends the 'T' command, the following sequence occurs:

User Input: 'T'
       |
       v
+------------------+
| ProcessCommand() |
+------------------+
       |
       v
+------------------+
| SendTestTrap()   |
+------------------+
       |
       v
+------------------------+
| SnmpTrapWithData()     |
| - Destination: All     |
| - Community: "public"  |
| - Type: Enterprise     |
| - Specific: 1          |
+------------------------+
       |
       v
+------------------------+
| TrapVarFunction()      |
| (Callback)             |
+------------------------+
       |
       +---------------------------+
       |                           |
       v                           v
+----------------+        +----------------+
| Varbind 1      |        | Varbind 2      |
| OID: 8174.1    |        | OID: 8174.2    |
| "Test msg 1"   |        | "Test msg 2"   |
+----------------+        +----------------+
       |                           |
       +-------------+-------------+
                     |
                     v
           +------------------+
           | SNMP Trap Packet |
           | Sent to Network  |
           +------------------+

Command Interface

The example provides a command processor accessible via:

Telnet on port 23
Serial console (Serial0 or Serial1)

Available Commands

Command	Description
D or d	Dump the SNMP MIB tree to the console
T or t	Send a test SNMP enterprise trap
logout	Close the current session

Authentication

The example includes a simple authentication callback that rejects login attempts where the username and password are identical.

SNMP Configuration

The example configures the following SNMP parameters:

System Description: "NetBurner SNMP Test Application"
Enterprise OID: 1.3.6.1.4.1.8174.2.40

The OID structure follows:

1.3.6.1.4.1.8174.2.40
| | | | | |    | |  |
| | | | | |    | |  +-- Application-specific ID (40)
| | | | | |    | +----- Product category (2)
| | | | | |    +------- NetBurner Enterprise Number (8174)
| | | | | +------------ Private enterprises
| | | | +-------------- Private
| | | +---------------- Internet
| | +------------------ DOD
| +--------------------- ISO/ORG
+----------------------- ISO

File Structure

simplesnmp/
    |
    +-- src/
    |       |
    |       +-- main.cpp           Main application source code
    |
    +-- mib/
    |       |
    |       +-- .index             MIB index file
    |       +-- RFC-1215.TXT       Trap conventions
    |       +-- RFC1155-SMI.txt    Structure of Management Information
    |       +-- RFC1213-MIB.txt    MIB-II definitions
    |
    +-- overload/
    |       |
    |       +-- nbrtos/
    |               |
    |               +-- include/
    |                       |
    |                       +-- predef-overload.h    Enables SNMP
    |
    +-- makefile                   Build configuration
    +-- readme.txt                 This file

Key Source Code Components

SNMP Initialization

SNMP is enabled through the predef-overload.h file:

#define ENABLE_SNMP (1)

The SNMP server object is declared globally:

SnmpServlet TheSnmpServer;

Trap Variable Callback

The TrapVarFunction callback populates custom varbind data in traps:

void TrapVarFunction(ASN *put_asn)
{
    put_asn->PutHeader(0x30);                    // Varbind sequence
    put_asn->PutOidFromString("1.3.6.1.4.1.8174.1");
    put_asn->PutOctetString("This is test message number 1");
    put_asn->FixUpHeader();
 
    put_asn->PutHeader(0x30);                    // Second varbind
    put_asn->PutOidFromString("1.3.6.1.4.1.8174.2");
    put_asn->PutOctetString("This is test message number 2");
    put_asn->FixUpHeader();
}

Sending Traps

Traps are sent using SnmpTrapWithData():

SnmpTrapWithData(
    IPADDR::NullIP(),        // Destination (NullIP = broadcast/configured)
    "public",                // Community string
    SNMP_ENTERPRISE_TRAP,    // Trap type
    1,                       // Specific trap code
    TrapVarFunction          // Callback for varbind data
);

Command Processor Callbacks

The command processor uses several callback functions:

+--------------------+----------------------------------------+
| Callback           | Purpose                                |
+--------------------+----------------------------------------+
| ProcessAuth        | Validate username/password             |
| ProcessCommand     | Handle user commands (D, T, logout)    |
| ProcessConnect     | Initialize new sessions                |
| ProcessPrompt      | Display command prompt                 |
| ProcessDisconnect  | Handle session termination             |
+--------------------+----------------------------------------+

Runtime Output

When running, the application displays periodic tick messages:

Web Application: Simple SNMP Example
NNDK Revision: x.x.x
Were here
Tick 1
Tick 2
Tick 3
...

Testing with SNMP Tools

You can test this example using standard SNMP tools:

Using snmpwalk (Linux/macOS)

snmpwalk -v 2c -c public <device_ip> 1.3.6.1.2.1.1

Using snmpget

snmpget -v 2c -c public <device_ip> 1.3.6.1.2.1.1.1.0

Receiving Traps

Configure an SNMP trap receiver to listen on UDP port 162 and send the 'T' command via Telnet to trigger a test trap.

MIB Files

The mib/ directory contains standard MIB definitions:

File	Description
RFC1155-SMI.txt	Structure and Identification of
	Management Information (SMI)
RFC1213-MIB.txt	Management Information Base for Network
	Management (MIB-II)
RFC-1215.TXT	Convention for Defining Traps

These files define the standard OIDs and data types used by SNMP.

Network Ports

Port	Protocol	Service
80	TCP	HTTP web server
23	TCP	Telnet command interface
161	UDP	SNMP agent (queries)
162	UDP	SNMP trap destination (outbound)