iPerf 2 (iperf2) Client is an Android frontend for iperf2, the widely used open-source network measurement tool. It bundles the real iperf2 engine, so your results are directly comparable with iperf2 running anywhere else.
Run an iperf2 network speed test from your phone or tablet: TCP throughput, round-trip latency, and - the part most tools skip - how both behave while the link is actually loaded.

This app is built around two things: responsiveness under real load, and comparing runs side by side.

Measure what your network actually delivers:

• Bounceback responsiveness testing. Measure how your round-trip latency holds up while the link is under load - bufferbloat (excess queuing delay from oversized buffers) is a common cause many overlook, but not the only delay pathology this can reveal
• Force a test onto a specific link - WiFi, Ethernet, or Cellular - to isolate which one is actually responsible for the delay you're seeing, instead of whatever the OS happens to pick
• Compare Wi-Fi vs Cellular delay at the tails, not just the average - tail latency is what actually defines user experience for mobile operators and device manufacturers
• Save runs into A/B/C/D slots, pick one as a reference, and compare against it: PDF and CDF distribution overlays plus an Earth Mover's Distance (EMD) score, so you can quantify a before/after router change, two networks, or two congestion-control settings, not just eyeball it
• TCP throughput testing with live charts
• UDP-L4S: congestion-controlled UDP with ECN testing, including live CE-mark rates, marking probability, and loss probability, for evaluating low-latency networking (this app doesn't do uncontrolled/plain UDP)
• Round-trip time reporting throughout
• Live dials and sparkline trends for throughput, RTT, congestion window, bytes in flight, and more
• Configurable host, port, duration, interval, direction, and congestion control; settings persist between runs

Who this is for: AP and access-network device manufacturers, broadband providers, mobile operators, managed service providers, mobile device manufacturers, retail device sellers (e.g. tablets), network engineers, students, and basically anybody in the communications business, directly or otherwise, who wants real numbers about their network and their devices.

Iperf2 is open source. Source code, documentation, the user manual, and desktop downloads are available at https://sourceforge.net/projects/iperf2/