How to Convert Pcap Data to .ts Files Using Python Script

Learn how to extract UDP streams from pcap files and save them as `.ts` files using a simple Python script with Scapy.
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Extracting UDP Streams from Pcap Files and Saving as .ts Using Python

When dealing with network analysis and packet inspection, you may sometimes find yourself needing to extract raw UDP stream data from .pcap files and save it into a .ts (MPEG Transport Stream) file format. While tools like Wireshark have built-in functionalities for this task, automating the process through scripting can save you time and effort—especially when working with multiple files or large datasets.

In this post, we will guide you through creating a Python script that leverages the powerful Scapy library to extract UDP streams from a pcap file and save them as .ts files.

Problem Overview

Imagine you have a .pcap file containing various network packets and you want to extract only the UDP streams for further processing or analysis. You may already know how to do this using Wireshark's graphical interface by following certain navigation steps, but now we’ll explore how to automate this using a script, which can prove invaluable when working with large datasets.

Prerequisites

Before we jump into the code, ensure you have the following:

Python installed on your system.

The Scapy library, which can be installed using pip:

[[See Video to Reveal this Text or Code Snippet]]

Solution: Python Script with Scapy

The following script will help you extract the UDP stream data from your pcap file and save it as a .ts file. Let’s break it down step by step.

Step 1: Importing Required Libraries

First, we will import the necessary libraries in our script.

[[See Video to Reveal this Text or Code Snippet]]

io is used to create an in-memory stream for writing the extracted data.

Step 2: Reading the Pcap File and Filtering for UDP Packets

Next, we’ll read our pcap file and filter out the UDP packets.

[[See Video to Reveal this Text or Code Snippet]]

Here, sniff captures packets from the specified pcap file with the offline argument, while the filter option ensures we only retain UDP packets.

Step 3: Processing Each UDP Session

Now, we will loop through each session of UDP packets, extract the payload, and write it to a .ts file.

[[See Video to Reveal this Text or Code Snippet]]

The sessions() method groups packets by five-tuple (source IP, source port, destination IP, destination port, and protocol).

We create a BytesIO object to temporarily store the raw data, which allows us to write multiple packets before saving to disk.

Step 4: Saving the Extracted Data to a .ts File

Finally, we will save the content of our buffer to a file:

[[See Video to Reveal this Text or Code Snippet]]

We generate a filename based on the five-tuple, replacing invalid characters to ensure it’s safe for the filesystem.

The wb mode opens our file for writing in binary format, ensuring that we write the raw data correctly.

Conclusion

By following the steps outlined above, you can effectively create a simple yet powerful Python script to automate the extraction of UDP streams from pcap files and save them into .ts files. This approach can significantly enhance your workflow, especially for tasks requiring repeated analysis of network packets.

Feel free to expand upon this script or adapt it to fit your specific needs. Happy coding!