Freedom251 › Network Testing Software
Flent
What Flent is
Flent is a free, open-source desktop tool for running network experiments on Linux and macOS. It brings netperf and similar benchmarking tools into predefined test runs, combines their measurements, and plots the results, with a primary focus on bufferbloat testing. Repeatable runs help make experiments consistent, while batch runs can automate a testing regime. Flent can also collect metadata from local and remote hosts and store it alongside plot data. Optional measurement series include CPU usage, WiFi, qdisc, and TCP socket statistics. Results can be saved as gzipped JSON or exported as CSV, Org tables, and plots. Plot exports use formats supported by matplotlib, including PNG, PS, PDF, and SVG. Most tests rely on netperf 2.6 or later; some use iperf, and the relevant utility must be available in PATH. For UDP measurements, Flent recommends irtt, whose server must run on target hosts. An interactive plot viewer is available, with PyQt5 and qtpy listed as optional macOS GUI dependencies. The project describes Flent as a way to make network experiments more reliable and easier to perform. It supports active TCP, UDP, and ICMP testing.
Who it suits
Flent suits network practitioners who want to run repeatable tests, especially when investigating bufferbloat. It can also help users who need batch experiments, supporting measurements, and plot or data exports on Linux or macOS.
What it does well
- Runs predefined, repeatable network tests and aggregates results.
- Batch runs can automate testing regimes.
- Captures host metadata alongside plot data.
- Collects CPU, WiFi, qdisc, and TCP socket statistics.
- Exports results as JSON, CSV, Org tables, and plots.
What to know first
- Most tests require netperf 2.6 or later.
- Some tests require iperf available in PATH.
- UDP measurements require an irtt server on target hosts.
Plans
| Plan | Billed and limits | Price |
|---|---|---|
| Flent | No paid plans or usage limits stated on the opened pages | Free |
As flent.org lists them, read 4 Oct 2026. The maker's own page has the final word.
Getting started
- Visit https://flent.org/ and choose an installation option for Linux, FreeBSD, or macOS.
- Install Flent using the option for your system.
- Make netperf 2.6 or later available in PATH for tests that use it.
- Make iperf available in PATH for tests that use it.
- For UDP measurements, run an irtt server on the target hosts.
- Install PyQt5 and qtpy on macOS if you want the optional interactive GUI.
Verdict
Choose Flent if you need a free, open-source desktop tool for repeatable network experiments, particularly bufferbloat testing. Its batch runs and varied outputs suit ongoing measurement work; plan to provide the relevant benchmarking utilities and an irtt server for UDP measurements.
Questions
How much does Flent cost?
Flent is free and open source. Its listed plan is free.
Which platforms does Flent support?
Flent is listed for Linux and macOS. The site also lists installation options for FreeBSD.
What does Flent test?
It supports active TCP, UDP, and ICMP testing, with a primary focus on bufferbloat.
Which tools do Flent tests need?
Most tests use netperf 2.6 or later, and some use iperf; the needed tool must be available in PATH. For UDP measurements, Flent recommends irtt, whose server must run on target hosts.
What formats can Flent export?
Results can be saved as gzipped JSON or output as CSV, Org tables, and plots. Plot formats supported by matplotlib include PNG, PS, PDF, and SVG.
Does Flent have a graphical viewer?
An interactive plot viewer is available. PyQt5 and qtpy are listed as optional GUI dependencies in the macOS installation instructions.
Facts from Flent's own pages
- Additional measurements
- It can collect CPU usage, WiFi, qdisc, and TCP socket statistics as secondary data series. · flent.org, 4 Oct 2026
- Automation
- Batch experiment runs can automate testing regimes. · flent.org, 4 Oct 2026
- Data capture
- It can capture metadata from local and remote hosts and store it with plot data. · flent.org, 4 Oct 2026
- Desktop GUI
- An interactive plot viewer is available, and the macOS installation instructions list PyQt5 and qtpy as optional GUI dependencies. · flent.org, 4 Oct 2026
- Intended users
- The project describes Flent as a tool for making network experiments more reliable and easier to perform. · flent.org, 4 Oct 2026
- Outputs
- Aggregated results can be saved as gzipped JSON or output as CSV, Org tables, and plots. · flent.org, 4 Oct 2026
- Plot formats
- Plots can be saved in formats supported by matplotlib, including PNG, PS, PDF, and SVG. · flent.org, 4 Oct 2026
- Purpose
- Flent wraps netperf and similar tools to run predefined network tests, aggregate results, and plot them, primarily to test for bufferbloat. · flent.org, 4 Oct 2026
- Repeatable tests
- It combines benchmarking tools into aggregate, repeatable test runs. · flent.org, 4 Oct 2026
- Supported installs
- The site lists installation options for Linux distributions, FreeBSD, and macOS. · flent.org, 4 Oct 2026
- Tools and dependencies
- Most tests use netperf 2.6 or later, while some use iperf; both tools must be available in PATH for the tests that use them. · flent.org, 4 Oct 2026
- UDP measurements
- The documentation recommends irtt for UDP measurements and says its server must run on target hosts. · flent.org, 4 Oct 2026
Where Flent stands on Freedom251
- Network Testing Software#11 of 33