Hi,
I'm looking for a good way to create a constant data stream that will occupy a bandwidth of about 2--5Mbit/sec between two remote hosts over the internet. I have full access to the hosts involved.
My first attempt to use scp to copy data from /dev/null on host A to /dev/null on host B, but scp says '/dev/null: not a regular file'. If something like that would work, I would be able to limit the bandwidth of this transfer in the router(s) involved so that it won't occupy all the bandwidth.
Of course, it would be better if I could limit the bandwidth on the sending side rather than dropping packages. I could probably write some program to do that, but since I have never programmed such a kind of network application, it would be rather time consuming. Maybe there's already a kind of tool around that can do this.
I need this to work around whatever settings my ISP has made 3 days ago that block my VPN connection so that I effectively can't reasonably work anymore. I do know what the problem with the connection is and that occupying some bandwidth would unblock the VPN; only there doesn't seem to be anything else I could about it.
On 30/05/2020 12:32, hw@gc-24.de wrote:
Hi hw,
I'm looking for a good way to create a constant data stream that will occupy a bandwidth of about 2--5Mbit/sec between two remote hosts over the internet. I have full access to the hosts involved.
My first attempt to use scp to copy data from /dev/null on host A to /dev/null on host B, but scp says '/dev/null: not a regular file'. If something like that would work, I would be able to limit the bandwidth of this transfer in the router(s) involved so that it won't occupy all the bandwidth.
You can't read from /dev/null. You get nothing from it. You're better off using /dev/random, for example. That will give you a continuous stream of random bytes.
However, that's not the focus of this. You want a sustain a stream of packets between two hosts. You're better off using UDP for this. And a good tool for generating such packets would be "iperf". It can measure bandwidth between two nodes more accurately.
Regards, Anand
On Saturday, May 30, 2020 12:46:02 PM CEST you wrote:
On 30/05/2020 12:32, hw@gc-24.de wrote:
Hi hw,
I'm looking for a good way to create a constant data stream that will occupy a bandwidth of about 2--5Mbit/sec between two remote hosts over the internet. I have full access to the hosts involved.
My first attempt to use scp to copy data from /dev/null on host A to /dev/null on host B, but scp says '/dev/null: not a regular file'. If something like that would work, I would be able to limit the bandwidth of this transfer in the router(s) involved so that it won't occupy all the bandwidth.
You can't read from /dev/null. You get nothing from it. You're better off using /dev/random, for example. That will give you a continuous stream of random bytes.
Oh, ok, yes, of course, that makes sense :)
However, that's not the focus of this. You want a sustain a stream of packets between two hosts. You're better off using UDP for this. And a good tool for generating such packets would be "iperf". It can measure bandwidth between two nodes more accurately.
Hm, iperf came to mind, and I looked at the manpage again. It doesn't seem to have a way to transmit/receive indefinitely, though it seems it has basically everything I'm looking for except for unlimited transfers. I'll try it out; I can always look at the source code and try to do about something about the limit if I need to.
On 5/30/20 5:46 AM, Anand Buddhdev wrote:
On 30/05/2020 12:32, hw@gc-24.de wrote:
Hi hw,
I'm looking for a good way to create a constant data stream that will occupy a bandwidth of about 2--5Mbit/sec between two remote hosts over the internet. I have full access to the hosts involved.
My first attempt to use scp to copy data from /dev/null on host A to /dev/null on host B, but scp says '/dev/null: not a regular file'. If something like that would work, I would be able to limit the bandwidth of this transfer in the router(s) involved so that it won't occupy all the bandwidth.
You can't read from /dev/null. You get nothing from it. You're better off using /dev/random, for example. That will give you a continuous stream of random bytes.
I would recommend to read from /dev/zero instead, it will give you a stream of zeroes. Using /dev/random is OK, but has one disadvantage in the OP case: you exhaust machine's accumulated entropy which may be more needed for other tasks (like ssh or ssl connections)...
Just my 2 cents.
Valeri
However, that's not the focus of this. You want a sustain a stream of packets between two hosts. You're better off using UDP for this. And a good tool for generating such packets would be "iperf". It can measure bandwidth between two nodes more accurately.
Regards, Anand _______________________________________________ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
On May 30, 2020, at 06:46, Anand Buddhdev anandb@ripe.net wrote:
You can't read from /dev/null. You get nothing from it. You're better off using /dev/random, for example. That will give you a continuous stream of random bytes.
/dev/random will block when you run out of entropy, so you won’t get a consistent flow of data after some time. /dev/zero should always return data, though. It I agree it makes more sense to use iperf.
-- Jonathan Billings billings@negate.org
On Sat, 30 May 2020 12:32, hw@... wrote:
Hi,
I'm looking for a good way to create a constant data stream that will occupy a bandwidth of about 2--5Mbit/sec between two remote hosts over the internet. I have full access to the hosts involved.
My first attempt to use scp to copy data from /dev/null on host A to /dev/null on host B, but scp says '/dev/null: not a regular file'. If something like that would work, I would be able to limit the bandwidth of this transfer in the router(s) involved so that it won't occupy all the bandwidth.
Of course, it would be better if I could limit the bandwidth on the sending side rather than dropping packages. I could probably write some program to do that, but since I have never programmed such a kind of network application, it would be rather time consuming. Maybe there's already a kind of tool around that can do this.
I need this to work around whatever settings my ISP has made 3 days ago that block my VPN connection so that I effectively can't reasonably work anymore. I do know what the problem with the connection is and that occupying some bandwidth would unblock the VPN; only there doesn't seem to be anything else I could about it.
Hmm, last time I had such issues (~10 years ago), I had a ssh-server on one side running, and used scp from the other side: scp -l [banwidth in Kbit/sec] /dev/zero [user@remote host]:/dev/null
For me at the time 150 kbit/sec was enough to keep my channel open.
Others used netcat (nc) in a script to get the similar results (feeding it "lines" at a certain rate to limit the traffic)
Have a nice weekend. - Yamaban
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Anand Buddhdev -
hw -
hw＠gc-24.de
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Jonathan Billings -
Valeri Galtsev -
Yamaban