iPhone Simulator - Simulate a slow connection? - iphone

Question

Is there a way to slow down the internet connection to the iPhone Simulator, so as to mimic how the App might react when you are in a slow spot on the cellular network?

Answer 1

How to install Apple’s Network Link Conditioner
These instructions current as of October 2019.
Warning: If you just upgraded to new version of macOS, make sure you install the very latest Network Conditioner (in Additional Tools for Xcode) or it may silently fail; that is, you will turn it on but it won’t throttle anything or drop any packets.
Update: As of Xcode 11, there may be an even simpler way to simulate network conditions on tethered devices; see this blog post. For how to affect simulated devices, continue below, as before.
Install Xcode if you don’t have it.
Open Xcode and go to Xcode › Open Developer Tool › More Developer Tools…
Download Additional Tools for Xcode (matching your current Xcode version)
Open the downloaded disk image and double-click the Network Link Conditioner .prefpane under “Hardware” to install it.
There we go!
Be sure to turn it on. You need to select a profile and enable the network conditioner.
Caveat
This won't affect localhost, so be sure to use a staging server or co-worker's computer to simulate slow network connections to an API you’re running yourself. You may find https://ngrok.com/ helpful in this regard.

Answer 2

"There's an app for that!" ;) Apple provides "Network Link Conditioner" preference pane that does the job quite well.
for Xcode versions prior to 4.3, the pane installer can be found in your Developer folder, e.g. "/Developer/Applications/Utilities/Network Link Conditioner", after installation, if daemon fails to start and you don't want to reboot your machine, just use sudo launchctl load /system/library/launchdaemons/com.apple.networklinkconditioner.plist
if you are already done with Developer folder, you can install the pane as a part of "Hardware IO Tools for Xcode" package available via Mac Dev Center additional downloads section.
Link to download page (you must log in with your Apple ID): https://developer.apple.com/downloads/index.action
(credits to #nverinaud)

Answer 3

An app called SpeedLimit
https://github.com/mschrag/speedlimit
Works great.
chris.

Answer 4

It also worth mentioning that Xcode also has a built in way for devices, not simulator.
Just go 'Devices and Simulator' (cmmd+shift+2)
Select your device
Scroll down til you find 'Device Conditions'
Set your desired profile
Hit Start
To have this working you need to install 'Network Link Conditioner' on your Mac. See steps mention in Alan's answer

Answer 5

I would argue that a slow connection isn't enough to simulate real-work mobile data network behaviour - since there is also much more packet loss, higher latencies and more dropped connections too.
Here is a handy script I found to configure the firewall to emulate these parameters:
http://pmilosev-notes.blogspot.com/2011/02/ios-simulator-testing-over-different.html
#!/bin/sh
if [ "$#" -ne "3" ]
then
echo "Usage:\n$0 <bandwidth in kpbs> <delay in ms> <packet loss ratio>";
exit 1
fi
BW=$1
DELAY=$2
PLR=$3
sudo ipfw pipe 1 config bw ${BW}Kbit/s delay $DELAY plr $PLR
sudo ipfw add 1 pipe 1 all from me to not me
sudo ipfw add 2 pipe 1 all from not me to me
echo "RETURN to stop connection noise"
read
sudo ipfw delete 1
sudo ipfw delete 2
exit 0
Some suggested values you can use:
Scenario
Bw (Kbit)
delay (ms)
pr (ratio)
2.5G mobile
(GPRS)
50
200
3G mobile
1000
200
0.2
VSAT
5000
500
0.2
Busy LAN on VSAT
300
500
0.4

Answer 6

There isn't a direct way to emulate a slow connection, unlike, say, the nice network connection emulator that blackberry developers enjoy. However, since your simulator's connection goes through your computer - you can simply focus on slowing down your computer's connection.
You'll want to achieve two things (depending upon your circumstances):
throttle your bandwidth
increase your latency
Maybe this will point you in right direction:
http://www.macosxhints.com/article.php?story=20080119112509736
There are some good open source solutions, too, but I so can't remember their names.
This question might help: How to throttle network traffic for environment simulation?

Answer 7

You can do it in really device through Xcode(14) settings
Debug -> Induce Device conditions -> Network Link -> select the Network you want