SMOLPy

Python rewrite of SMOL — a Network Description Language and Discrete-Event Simulator for industrial Measurement-Diagnostics-Control (MDC) networks.

SMOLPy lets you describe a network topology in pure Python, define traffic flows, and run a discrete-event simulation (powered by SimPy) that produces real metric time-series. A built-in Dear PyGui desktop dashboard shows the topology and live metric charts as the simulation runs.

Install

uv sync          # installs all runtime + dev dependencies

Quick start

from smolpy import Network

net    = Network("office-net")
host_a = net.adapter("host-A", ip="10.0.0.1")
server = net.adapter("server",  ip="10.0.0.10")
sw1    = net.switch("sw1", ports=8, mode="store-and-forward")

net.link(host_a, sw1, speed=1_000,  length=5)   # speed in Mb/s, length in metres
net.link(server, sw1, speed=10_000, length=2)

host_a.sends(to=server, rate=8_000, size=1_518, pattern="constant")

net.observe("throughput",  on=server, every=100)   # sample every 100 ms
net.observe("queue_depth", on=sw1,    every=50)

result = net.simulate(duration=30_000, live=True)  # 30 s simulation with live dashboard
result.report()                                     # print summary table to terminal

Run it:

uv run smolpy run my_script.py

Quick demo

smolpy demo          # built-in 3-client scenario, text mode, no script needed

Where to go next

• DSL Reference — topology builders, traffic generators, observations, and simulation control
• SMOL Language Reference — describe a network in a standalone .smol file, no Python required
• MQTT — publish/subscribe messaging model
• Modbus TCP — master/slave polling model
• Simulation Engine — how the discrete-event model works under the hood
• Dashboard — the live Dear PyGui desktop view
• Examples — nine ready-to-run scenarios
• Architecture Decision Records — the design decisions behind SMOLPy's structure