QCheck is fine, but a little short and opaque for my liking.
I'll suggest iperf.
E.g.
server: iperf -s
client: iperf -c server -l 64K -t 12 -i 3 -r
-l 64k: send 64k of data at a time (same as Windows typically)
-t 12: run for 12 seconds
-i 3: report performance every 3 seconds
-r: transmit to server, then reverse direction