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Show HN: Slowy app, Real-world connection simulator and bandwidth limiter (slowyapp.com)
104 points by potomak on Nov 30, 2011 | hide | past | web | favorite | 32 comments

You don't need an app for this. I wrote a shell script which uses ipfw for exactly this purpose (Most probably this app uses ipfw too) here is the script- https://gist.github.com/1409218

Run it like

   throttle -p 3000 -d 1000ms -s 256Kbit/s start
p - Port

d - network delay you want

s - speed

For designers working with css, going to the command line can be daunting. So you could wrap this in a nice app on the dock or the menu bar, and maybe you'd like a couple of euro for your time and writing some support documentation..

I know :) The comment made me smile because I wrote the script for a client who is a designer.

I used to use the ipfw commands directly. I didn't want the client to remember the syntax and also starting and stopping the throttling involved a couple of commands which can go wrong. So I wrote this and also had some default values so that he can just do throttle start and throttle stop

This is really nice, thank you. Just curious though, any reason why you don't make a full featured github repo for it so people could follow updates in future, suggest changes etc?

This was sufficient for my use. I just wrote it couple of days back. I can't think of any more features (except restricting bandwidth for upload also). So having a repo didn't even cross my mind

Umm... Lion does this out of the box w/ XCode:


It's called the "network conditioner" and it does lag, packet loss, latency, bandwidth limiting, and more. And it's free.

So how is it different from /Applications/Utilities/Network Link Conditioner ?

On the homepage (6th feature) "As Slowy mainly is a GUI for built-in OSX tools, it will occupy only few MB of your RAM and nearly 0% of your CPU."

I'm pretty sure Network Link Conditioner is the same.

I think the author would be better off giving it away for free, earning goodwill and making a name for his dev shop, then releasing other apps to all the people who now are aware of him.

Or sell it, and earn good will because he sells good products?

It's possible that within the Mac App developer community he might earn goodwill by giving it away, but I don't think it's going to make a difference for the average users.

I can't recall the names of any dev shops for the OSX products I have purchased, much less the ones I use for free.

I have no problem with people selling simple tools that make built-in features more accessible.

This also works on 10.5 and 10.6

The per-port throttling is different, the rest is quite similar ( that's what I get from reading the page ).

I'd like to have something like this for Linux. Anyone got any tips how to set something like this up? Command line and kernel option hacking preferred to GUI gadgets.

I would need to test my virtual-connection-over-UDP code with packet loss, latency and incorrect packet order delivery and I really wouldn't want to write code inside my app to test.

Also worth being aware of - NIST Net: http://snad.ncsl.nist.gov/nistnet/

Lets you set up a linux box to act as a configurable router that does network emulation. Useful if you want to test devices that don't have their own emulation options.


Good lord, you really do learn something new every day with linux. Thanks!

Excellent. I sort of expected an utility like this to be part of a "standard installation".

Are there good examples of using tc to emulate a crappy connection?

Sure. You can add jitter, packet loss, duplication, corruption, shaping, reordering, prioritisation. This page has examples: https://www.linuxfoundation.org/collaborate/workgroups/netwo... (netem is the kernel framework, it is to tc what netfilter is to iptables). The examples apply to outgoing traffic, search for ifb0 for a way to apply them to incoming traffic.

i believe this tool (and the one in Lion/XCode) uses ipfw+dummynet, which is available also for linux/openwrt and windows at http://info.iet.unipi.it/~luigi/dummynet/ (you can find also some documentation material there).

Seems to be a trend to wrap a lesser known commandline tool in a cocoa app and knock it out for a couple of quid to arts graduates. Someone did a cocoa version of guard recently. That other guy tried to make a system preferences pane for the hostfile, but apple wouldn't let him. I'm sure there have been others.

At least this guy has the decency to point out that it's already built into OS X right there on the landing page ;)

If you need to do this stuff to a saturated gigabit pipe in both directions, then may I suggest the superbly named 1U Network Nightmare, yours for only $9999.


I use Charles (http://charlesproxy.com) for this sort of thing - offers a few more features than Slowly

Available on Windows / OS X / Linux

One the downside it needs Java!

See also Speedlimit: http://mschrag.github.com/

Does the same thing and is free!

I really liked the design of this page. The gray/white/red color scheme was right for this product IMO.

Hi guys, I'm the developer of the application. Thank you for all your comments. I'll take them into consideration while trying to improve the rough edges and missing features of Slowy for the next update. I'll update the website soon (http://slowyapp.com), completing the FAQ section and adding a new blog section.

For Windows I would recommend NetLimiter[1]. Really nice way to check speeds and connections as well as remote controlling the bandwidth on other computers (with a NetLimiter client on both).

[1]: http://www.netlimiter.com/

The website has some layout problems when viewed from the iPhone, and, more importantly, it appears to only have a description, but no Download button or a pricing information.

It's a mac app, you wouldn't want to download it on your iPhone anyways :)

It doesn't limit upload rate. Thats too bad.

i was always a big fan of sloppy http://www.dallaway.com/sloppy/ and hadn't bothered to look for alternatives, but the other projects here are equally heartening and have... less java

Please consider posting some mac app store stats after some time, thanks!

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