Can anyone tell difference between iPerf and iPerf3? while using it with client-server python script,what are the dependencies?And what are the alternatives to iPerf?
iperf vs iperf3 from wikipedia

A rewrite of iperf from scratch, with the goal of a smaller, simpler
  code base and a library version of the functionality that can be used
  in other programs, called iperf3, was started in 2009. The first
  iperf3 release was made in January 2014. The website states: "iperf3
  is not backwards compatible with iperf2.x".

Alternatives are Netcat, Bandwidth Test Controller (BWCTL), ps-performance toolkit, iXChariot, jperf, Lanbench, NetIO-GUI, Netstress.
Iperf3 commands with python script