$ iperf3 -c 127.0.0.1
Connecting to host 127.0.0.1, port 5201
[  4] local 127.0.0.1 port 28117 connected to 127.0.0.1 port 5201
[ ID] Interval           Transfer     Bandwidth
[  4]   0.00-1.00   sec   540 MBytes  4.53 Gbits/sec
[  4]   1.00-2.00   sec   627 MBytes  5.25 Gbits/sec
[  4]   2.00-3.00   sec   630 MBytes  5.30 Gbits/sec
[  4]   3.00-4.00   sec   627 MBytes  5.25 Gbits/sec
[  4]   4.00-5.00   sec   622 MBytes  5.23 Gbits/sec
[  4]   5.00-6.00   sec   653 MBytes  5.47 Gbits/sec
[  4]   6.00-7.00   sec   680 MBytes  5.72 Gbits/sec
[  4]   7.00-8.00   sec   683 MBytes  5.73 Gbits/sec
[  4]   8.00-9.00   sec   664 MBytes  5.57 Gbits/sec
[  4]   9.00-10.00  sec   664 MBytes  5.56 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth
[  4]   0.00-10.00  sec  6.24 GBytes  5.36 Gbits/sec                  sender
[  4]   0.00-10.00  sec  6.24 GBytes  5.36 Gbits/sec                  receiver

iperf Done.