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nuttcp vs Flent: catalog facts
nuttcp	Flent
Free Free and open source.	Free Free to download and use, with the source published on GitHub.
Windows, macOS, Linux, Command line	Linux, Command line
Handles high-throughput TCP and UDP testing beyond typical consumer speed tests Cross-platform command-line tool suited to scripting and automation	Repeatable aggregate tests built on netperf and iperf Interactive GUI and extensive plotting
Requires installing and running the tool on both ends of the connection Command-line only, with a learning curve for new users	Needs netperf or iperf and a test server on the other end Aimed at technical users rather than a quick speed check
Downloadable app	Downloadable app
Open source	Closed source
License not stated	License not stated
Not stated if an account is needed	No account needed
Not stated if it works offline	Works offline
Official website Full listing and sources Checked September 22, 2026	Official website Full listing and sources Checked September 23, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.