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#_connects src_IP dst_IP When_It_Happened_Secs
Real gurus don't need fancy tools like iftop or jnettop.
see http://iptraf.seul.org/ for all kinds of documentation and screenshots
Note, the [remotePort] should be opened in the firewall first. First, start the destination box listening, then fire off the sending box. Data from the /dev/zero device in memory of the source machine is read out using dd, sent over the network with nc, and read back in from the other side of the network with nc, going to the /dev/null device. Essentially, it is a memory-network-memory copy operation, the output of dd will tell you how fast your network really is performing.