SNMP TRAP/INFORM application example:
The application below shows the management system alarming component as a standalone example on how traps are received and generated for both SNMP TRAP and INFORM and can be used as a testing tool within a lab or network management software development.

SNMP Trap Receiver (Windows)

A Windows server desktop application for receiving and inspecting SNMP traps across SNMPv1, SNMPv2c, and SNMPv3. It provides a clean GUI with start/stop controls, dark/light themes, CSV persistence of listener settings, and a dynamic table that expands to show every varbind carried in each trap.

It’s purpose is three fold; it allows for real network or servers to send SNMP traps to this app and to display the received traps for testing. Secondly the trap generator allows for custom or vendor traps to be configured and send to a lab NMS and development of an NMS for small scale testing with the absence of real devices generating SNMP traps.

Key features

• Multi-version support: Toggle between SNMPv1, SNMPv2c, and SNMPv3.

• SNMPv3 ready: Configure user, security level (noAuthNoPriv, authNoPriv, authPriv), auth/priv algorithms (MD5/SHA… AES/DES/3DES), keys, and remote EngineID (hex).

• EngineID handling for traps:

  • If you provide a remote EngineID, the app binds credentials to it immediately (recommended for TRAPs).

  • If not provided, the app auto-learns EngineID from incoming packets and binds on the fly, then logs an info row.

• Shows undecodable v3 traps: Even if credentials are wrong, the app inserts a row noting “unable to decode” (with the USM error) so you can see activity and debug.

• Dynamic varbind columns: The table starts with base columns (Time, Version, Source, Community/User, Trap OID) and adds new columns per OID as traps arrive, so mixed traps with different varbind sets are handled gracefully.

• Start/Stop without hangs: Background listener runs in a QThread; a tiny UDP “wakeup” packet cleanly unblocks the dispatcher on stop.

• Theme toggle: Global Light/Dark (Fusion) palette switcher.

• CSV persistence: Saves/loads listener configuration (version, address/port, communities, v3 credentials, EngineID, theme) to receiver_settings.csv.

• “Clear Table” button: Quickly reset the view and remove all dynamic varbind columns.

How it works

• Uses pysnmp’s asyncore UDP transport and ntfrcv.NotificationReceiver to capture traps.

• Registers observers:

  • rfc3412.receiveMessage:request to learn source address and remote EngineID early.

  • rfc3414.processIncomingMsg to surface USM failures as visible “info/error” rows.

• On each decoded trap, the app extracts snmpTrapOID.0 (or falls back to the first varbind) and prints every varbind (OID → pretty-printed value).

• A column cache maps OIDs → table columns; unseen OIDs create new columns on demand.

Usage

1. Choose SNMP Version.

2. Set Listen Address (e.g., 0.0.0.0) and Port (e.g., 162 or a higher unprivileged port like 5162 during development).

3. For v1/v2c: set Community.

4. For v3: set User, Security Level, Auth/Priv algorithms/keys, and optionally Remote EngineID (hex).

5. Click Start to begin listening; Stop to end; Clear Table to reset the view.

6. Use the Theme dropdown to switch between Light/Dark.

Notes & tips

• Permissions: On many systems, port 162 requires elevated privileges; during testing, use a higher port on both sender and receiver.

• v3 traps & EngineID: TRAPs are one-way; the receiver can’t discover EngineID via time sync like INFORMs. Providing a matching Remote EngineID is the most reliable approach. If omitted, the app auto-learns it from incoming packets and binds credentials for subsequent traps.

• Auth/Priv key lengths: Ensure keys meet the chosen algorithm’s expectations and match the sender exactly.

• Troubleshooting:

  • If you see an “unable to decode” v3 row, check user/algorithms/keys/engineID.

  • Firewall/AV may block UDP; allow inbound on the chosen port.

  • If stop ever seems slow, it’s waiting for the dispatcher loop to wake; the app sends itself a tiny UDP packet to exit promptly.

SNMP Trap Generator (Windows) - Testing and Educational purposes only

A desktop utility for composing and sending SNMP traps over SNMPv2c and SNMPv3. It’s designed for testing receivers, validating credentials, and simulating real-world events. The app provides a table to define one or more traps (each with custom varbinds), batching/repeat controls, v3 security options, a theme switcher, live log, and CSV persistence.

Key features

• SNMP versions: Send traps using SNMPv2c (community) or SNMPv3 (USM).

• SNMPv3 security: Choose security level (noAuthNoPriv, authNoPriv, authPriv) with algorithms:

  • Auth: None, MD5, SHA, SHA224, SHA256, SHA384, SHA512

  • Priv: None, DES, 3DES, AES128, AES192, AES256

• Fixed EngineID (v3): Supply a hexadecimal EngineID so receivers that expect a stable engine can authenticate/decrypt your TRAPs reliably. The app sets it in a version-compatible way across pysnmp builds.

• Trap composition table: Define multiple traps:

  • Column 1: Enabled checkbox

  • Column 2: Trap OID (numeric or named, e.g. 1.3.6.1.6.3.1.1.5.3 or SNMPv2-MIB::coldStart)

  • Column 3: VarBinds as OID=value pairs, comma-separated

• Repeat & pacing: Send each enabled trap N times with a configurable inter-trap gap (ms).

• Live log: Progress and errors stream into a log pane; Clear Log button included.

• CSV persistence:

  • traps.csv stores your trap rows (enabled flag, Trap OID, VarBinds).

  • generator_settings.csv stores target, timeouts, version, v3 credentials and EngineID, and theme.

  • Files auto-load on start and auto-save as you edit.

• Light/Dark theme: Toggle via the top bar (Fusion palette).

VarBind input syntax

Write varbinds as a comma-separated list of OID=value. OIDs may be numeric or names; values support lightweight typing:

• Strings: "hello" or 'hello'

• Hex bytes: 0x48656c6c6f (even length)

• IP address: ip:192.0.2.10

• OID value: oid:1.3.6.1.2.1.1.5.0

• TimeTicks: tticks:12345

• Integers / Counters / Gauges: 42, c32:100, c64:1000, u32:7

Usage

1. Pick Version (v2c or v3) and set Target host/port (e.g., your receiver).

2. Configure Timeout/Retries.

3. For v2c: set Community.
   For v3: set User, Sec Level, Auth/Priv algos and keys, and EngineID (hex).

4. Add or edit trap rows, mark desired ones Enabled.

5. Choose Repeat and gap (ms), then click Run.

6. Watch progress in Log. Use Clear Log to reset.

Tips

• During development on Windows, prefer an unprivileged port (e.g., 5162) on both generator and receiver.

• For SNMPv3 TRAPs, a fixed EngineID often avoids “unknownEngineIDs” on receivers and speeds up successful decryption.

• Auth/Priv keys must match the receiver’s expectations (algorithm + key material).

• If you see an error in the log, verify OIDs, varbind syntax, credentials, and network/firewall rules.

This tool pairs nicely with the companion SNMP Trap Receiver app: keep the receiver open on the chosen port and security settings, then use the generator to simulate events end-to-end.contents.