I Built a Free, Self-Hosted SNMP Toolkit — Now With Real-Time WebSocket Push

Published: 3 days ago (February 22, 2026 at 08:01 AM EST)

5 min read

Source: Dev.to

What Is Trishul SNMP?

A self‑hosted SNMP dev toolkit that combines five tools into one clean web UI.

What	Instead of
SNMP Simulator (UDP agent)	`snmpsim` + CLI config
Walk & Parse → JSON	`snmpwalk` + manual OID lookup
Trap Sender + Receiver	`snmptrap` + `snmptrapd`
MIB Browser (tree view)	iReasoning MIB Browser ($500+)
MIB Manager (upload/validate)	Text editor + manual dependency hell

Stack: Python 3.11, FastAPI, pysnmp, pysmi, Bootstrap 5, Docker.

# Install in one command
curl -fsSL https://raw.githubusercontent.com/tosumitdhaka/trishul-snmp/main/install-trishul-snmp.sh | bash

Then open http://localhost:8080. Default login: admin / admin123 — change it immediately in Settings.

What’s New in v1.2.4

⚡ Real‑Time WebSocket Push — Polling Is Dead

The biggest architectural change: the entire frontend is now event‑driven.

Before: Every page polled the backend on a setInterval — dashboard every 30 s, simulator every 5 s. Stale data was common. Switching pages caused spinners.

After: A single persistent WebSocket connection at /api/ws. The backend broadcasts state changes the moment they happen. Dashboard, Simulator status, and Trap Receiver all update instantly — no refresh needed.

Browser ←──── WS push ────── FastAPI /api/ws
                                    │
                              broadcasts on:
                              - trap received
                              - simulator start/stop
                              - MIB uploaded
                              - stats change

The navbar shows a live green dot when the WebSocket is healthy. On reconnect, the backend sends a full_state message to re‑seed everything — so you never see stale data after a network hiccup.

Why this matters for devs: If you’re building a trap handler and sending test traps from the UI, you now see the counter increment on the dashboard in real time. No F5 needed.

📊 Live Activity Stats Dashboard

A new 8‑counter row on the dashboard shows everything happening in your session:

Counter	Description
SNMP Requests	Total polls served by the simulator
OIDs Loaded	OIDs currently in memory across all loaded MIBs
Traps Received / Sent	Live trap counters
Walks Executed	How many SNMP walks you’ve run
OIDs Returned	Total OIDs returned across all walks
MIBs Uploaded / Times Reloaded	MIB management activity

All counters update via WebSocket push. They’re also file‑backed — they survive container restarts so you don’t lose your session history.

⚙️ Settings — Three New Cards

App Behaviour

Two toggles: auto‑start Simulator and auto‑start Trap Receiver on container boot.
Configurable session timeout (60 s – 86 400 s).
Settings persist to app_settings.json and take effect on next restart.

Stats Management

Export all counters as JSON (useful for logging test session results).
Reset counters to zero for a clean baseline before a test run.

About

Version, author, and description pulled live from the backend — always in sync with what’s actually deployed.

🐛 Notable Fixes

Issue	Fix
Timestamp bug – Trap Receiver showed `1970` for `Last Received` when the backend returned a Unix epoch `0`.	Guarded the value and now display `--` when epoch is zero.
Traps Sent undercount – Stats were only incremented in the frontend; API‑direct trap sends never updated the counter.	Backend now broadcasts stats after every successful trap send.
Dashboard spinners on page switch – WS `full_state` fired before `DashboardModule.init()` registered its listener, leaving tiles stuck as spinners.	Always seed via REST on init, regardless of WS state.
MIB Browser state conflict – Navigating to the Browser from Walk & Parse (with a pre‑filled OID) sometimes logged `Could not find node` because the previous session’s pending tree state conflicted.	Clear `pendingSelectedOid` and `pendingExpandedNodes` when a programmatic OID search is present.

Who Is This For?

NMS / backend developers – Need a real SNMP agent to poll without actual hardware, or need to fire specific trap OIDs to validate handler code.
DevOps / integration engineers – Need to test SNMP monitoring integrations in CI/staging environments.
Network engineers – Want to explore MIB structures interactively — search by OID, by name, or by description — and understand what traps a device can fire before it’s on the floor.

What It’s NOT For

Production 24/7 monitoring → use Zabbix, LibreNMS, PRTG.
Enterprise NMS → use SolarWinds, Cisco Prime.
High‑availability trap collection at scale → use dedicated platforms.

Trishul is a developer and testing tool, not a production monitoring system.

Quick Architecture

Browser (8080)
   │ HTTP + WebSocket
   ▼
Nginx (static files + reverse proxy)
   │ REST + WS
   ▼
FastAPI Backend (8000)
   ├── MIB Service (parse, validate, search)
   ├── SNMP Simulator (UDP 1061)
   ├── Trap Manager (send + receive on UDP 1162)
   ├── Walker (SNMP walk client)
   └── WebSocket hub (/api/ws)

Everything runs in Docker with host network mode so the SNMP UDP ports (1061, 1162) are reachable from the host.

Try It

# One‑command install
curl -fsSL https://raw.githubusercontent.com/tosumitdhaka/trishul-snmp/main/install-trishul-snmp.sh | bash

# Access at
http://localhost:8080

🐙 GitHub — tosumitdhaka/trishul-snmp
💬 v1.2.4 Announcement & Discussion — View discussion
📋 Full Changelog — View changelog

If it’s useful, a ⭐ on GitHub goes a long way — it helps other devs find the project.

Happy to answer questions in the comments about architecture decisions, the pysnmp/pysmi integration, or the WebSocket implementation. 🔱