I'm trying to understand bitcoin
RPC Peer to Peer protocol to implement SPV on a web-application that should receive crypto payments.
The problem is that on the examples I found, examples are about RPC requests to a full node I'm supposed to own, but I want to query other nodes (nodes I have no user:password for).
As far as I understand, bitcoinj and full wallets connects to the network make requests to them without user:pass, but I could not found how that requests are built, and how can I test and try them using curl to learn how it works.
Is there a api documentation I can check and a list of nodes I can query? Also, I understand that to establish a connection I should send the
version request, but from curl I don't have a "version".
I've found this documentation about the protocol, but I've found no way to test that out in simple terms (like curl), to know what is being sent-received.
I want to understand what queries I can make using this protocol without running a full node.
It seems that what I wanted to know if it is possible to learn about the bitcoin protocol making test calls with curl to full-nodes (not RPC). It seems that it is not possible.