How to Use iOS Packet Trace and Packet Sniffing on iPhone

Using a packet trace or packet sniffer on iOS can be helpful during testing. Here we cover what packet trace and packet sniffing are — and how to use them in Perfecto. 

What Is a Packet Trace?

A packet trace is a record of traffic traveling across your network. Using a packet trace is helpful when you're debugging an application. It's also helpful while a test is running.

iOS has built-in support for packet traces. (So does Mac.) 

Packet trace is also related to packet sniffing. 

What Is iOS Packet Sniffing?

Packet sniffing is used to monitor traffic on an iPhone. 

Dumped network traffic contains important information regarding your device’s network connection – from DNS request and response times to overall network latency and errors, and even full HTTP/HTTPS* conversations (without the need to set a proxy!).

*Encrypted, unless you have access to the web server’s SSL key.

Keep reading to learn about iOS packet trace and iPhone packet sniffing.

Related Reading: 3 Steps to Debug and Test Your iOS App in the Cloud >>

How to Capture a Packet Trace on iOS

Here's how to enable packet capture on iOS. 

1. Establish a DevTunnel Session

First, you need to establish a DevTunnel session on the device. Once you have an iOS device opened…

Next, click on the “DevTunnel” widget on your left, and wait for the progress to reach 100%.

2. Determine the UDID

Now determine the UDID of the device. The easiest way is to look in the “Information” window of the device. Click on the “Information” button:

And then copy the UDID of the device by clicking on the “Copy to Clipboard” icon:

3. Create the Remote Virtual Interface

Now that we have the device’s UDID, we can create the remote virtual interface. You can do this by using a tool called rvictl*. rvictl is a remote virtual interface tool which can be used to start a packet capture on iOS devices.

rvictl is part of the XCode command line utilities. Install them if you haven't yet!

4. Determine the Usage

Let's go over the usage:

So, when you would like to start a remote capture, assuming our UDID is (for example) 002daa400df726c38aac1,

the usage would be:

            rvictl -s 002daa400df726c38aac1

Once executed, rvictl will inform us of the new interface it has created

Running the ‘ifconfig’ command reveals the new interface.

📲 Try Debugging With Perfecto

How to Use iPhone Packet Sniffing

1. Start iPhone Packet Sniffing

Now you can start iPhone packet sniffing to see network traffic over the device. We can view the traffic by executing the following command:

            tcpdump -n -t -i rvi0 -q -A tcp

As soon as the command is executed, we start seeing the iPhone's packet sniffing data printed to our console. Packet trace magic!

2. Record the Traffic

Recording the traffic to a PCAP file can also be easily achieved with tcpdump by using the -w flag. This can be very useful when recording the traffic while running your daily tests.

The following command would start a network sniff on the device and record the traffic to a pcap file:

            tcpdump -n -t -i rvi0 -q -A tcp -w out.pcap

3. Use Wireshark iOS App to Analyze Traffic

Another tool that can help developers analyze the traffic is the Wireshark iOS app. Simply open Wireshark and select the rvi0 interface:

4. Look at the Sniffed Packets

Once the capture has been started, we can immediately see the sniffed packets from the device:

And even reconstruct HTTP conversations on the fly:

There are many other tools that can help you read packet trace data from this remote virtual interface. A full list can be found in Apple Technical Q&A.

Go Beyond Packet Capture on iOS

And that's how you can conduct an iOS packet trace. Now that you're an expert in iPhone packet sniffing, learn some other tips, tricks, and hacks for mobile apps with Perfecto's Remote Device Access.

Or, try debugging yourself with Perfecto. Perfecto can also help you:

• Automate more tests.
• Apply real user conditions to your tests.
• Accelerate your testing.

To streamline your overall testing experience, try a free 14-day trial of Perfecto today. 

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Related Content

• 3 Steps to Debug and Test Your iOS App in the Cloud
• How To Use a HAR File to Find The Hidden Performance Bottlenecks in Your App
• Debugging From Your IDE is Much Easier Now – It’s On the Cloud