Why this project exists
I used to work on an IMS project, which involved multiple machines. In nutshell, IMS stands for IP Multimedia Subsystem and it is a SIP based implementation of voice service in LTE mobile network. I don't want to explain what IMS is, as it is totally out of the scope of this post, but if you are interested the page for IMS in Wikipedia is a good start.
Tracing a voice call in an IMS setup involves packet capturing on four different machines, which turned out to be a pretty tedious job. Up to now, my work required to collect PCAP files from one or maximum two remote machines. To achieve this I used a simple bash script, which starts tcpdump over SSH and redirects the output to a Wireshark instance running locally. You can find the script in my dotfiles shared on GitHub.
Using this script for capturing traffic from four remote machines was not very straightforward. I often ended up forgetting to start the script for any of the machines, forget to save the file, close wireshark by mistake and so on.
At this point the idea for rpcap was born.