How to understand the first reply of a node

Question

I have send my version message to a bitcoin node and the hexdump of his answer was this:

https://pastebin.com/QBNaeS0g

Maybe this is a network related question but I want to know the version used by this node and how did you come with it.

Answer 1

Easiest way to understand the response of other nodes IMO is using Wireshark and follow the below steps:

1. Install Wireshark

2. Capture packets according to the network you will be using on this system when Bitcoin full node connects with the network.

3. Launch Bitcoin Core

4. Stop capturing packets once the node is connected to few peers

5. Filter captured data in Wireshark with keyword "bitcoin"

6. Check the details of version packet sent by other node

7. In the middle section you have all the details in readable format and last section is bytes view. Once you select any information in the middle section, relevant info will be highlighted in the byte view as the selected bytes.

According to my understanding, src/clientversion.cpp decides the version message in Bitcoin Core and src/init.cpp helps in sharing this information.

There is one more tool for conversion of such data but I have not used it enough. I think it can be helpful while experimenting with Bitcoin: https://github.com/gchq/CyberChef