By default, Iperf perform data transmission from the client to the server.
With the current implemnation of Iperf, it is possible to do two-ways data transmission using the so called iperf "client" thanks to the parameter "-r" or "-d".
In my opinion, it would be very interesting to be able to choose whether we want to receive or whether we want to send data from the "client" to the "server".
This would be very convenient in a test network environement as an Iperf server could be installed somewhere on the network. All the actions could therefore be performed on the Iperf client located on a local PC.