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Need help in getting iperf/jperf to test network performance

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Occasional Visitor
Following Doug Reid's articles in April 2008 about measuring network performance using iperf and jperf, I have not been successful in using these applications to test my network's performance before putting installing a new DIR-655 router, gigabit nic, and wireless n client adapter. Can someone help trouble shoot what I am doing wrong?

Re iperf: The website for this app, http://dast.nlanr.net/Projects/Iperf/ is "not available" according to IE. So, I downloaded from http://www.noc.ucf.edu/Tools/Iperf/ version 1.7.0. However, when I click on the downloaded file, iperf.exe, a black command window opens, but does not yield a prompt. It closes,automatically after about 10 seconds. The title of the window is merely the path of the iperf.exe file on my computer.

Re jperf: I was able to download the zip file to both my laptop and desktop. After unzipping the folder (and also, after downloading and installing Java) I opened up the file by double clicking on jperf.bat. The network performance measurement graphical tool opened up. I set the desktop as the server and clicked on the test button. I also ran ipconfig to obtain the ip address of the desktop. I then opened up jperf on the laptop, chose client mode, and entered the IP address of the desktop under "server address." When I clicked on the "run iperf" button, I received an "invalid argument" message as follows:

bin/iperf.exe -c -P 1 -i 1 -p 5001 -f k -t 10 -T 1
connect failed: Invalid argument.

Why is this not working? What makes the argument invalid? Do I need to supply additional information? Could my firewall be blocking access? How would I know?

I am anxious to set up my new router, and wireless client adapter, but I want to be able to measure current network performance before doing so. Can anyone help?




Regular Contributor
Jperf steps

You're on the right track. Follow these steps and you'll be running throughput tests in no time.

1.Stick with jperf. You don't need iperf.
2.Open TCP port 5001 on both your desktop and laptop firewalls.
3.Double click jperf.bat on both PCs to start the program.
4.On your desktop, Choose iPerf Mode = Server and click Run Iperf!
5.On your laptop, Choose iPerf Mode = Client.
6.On your laptop, enter the IP address of your desktop in the Server address field.
7.On your laptop, click Run Iperf!

You should now see text output at the bottom of the jperf display and the chart plotting data.

These instructions are for running jperf between two PCs behind your DIR-655.

To run jperf through the DIR-655, you'll need to configure port forwarding for TCP port 5001 to the IP address of the PC inside the NAT.

Good luck!


Occasional Visitor
jperf steps

Thank you so much! Opening up port 5001 on both machines did the trick. It took me a while to figure out how to do that; but once done, I was able to see that my old 802.11b Linksys is transferring data at a rate of 4.04 megabits per second. Other Jperf tests showed that it takes 2.1 secs to transfer one Mbyte. That works out to just over 35 mins./Gbyte! That explains a lot of the transfer problems I have been having between the two computers.

Once I hook up the DIR-655 I will want to test it. You wrote that to do this I would need to "configure port forwarding for TCP port 5001 to the IP address of the PC inside the NAT." Can you explain how this is done or is it likely to be self-evident to a non-techie like myself once I set up the D-Link router?


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