$ iperf -c localhost
------------------------------------------------------------
Client connecting to localhost, TCP port 5001
TCP window size: 2.50 MByte (default)
------------------------------------------------------------
[ 3] local 127.0.0.1 port 44366 connected with 127.0.0.1 port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.0 sec 62.9 GBytes 54.1 Gbits/sec
$ iperf -s -B 127.0.0.1
------------------------------------------------------------
Server listening on TCP port 5001
Binding to local address 127.0.0.1
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
[ 4] local 127.0.0.1 port 5001 connected with 127.0.0.1 port 44366
[ ID] Interval Transfer Bandwidth
[ 4] 0.0-10.0 sec 62.9 GBytes 54.0 Gbits/sec