A "Hello World" of bitcoin? I would like to write a very simple program in bitcoin. I thought a simple C program that accepts the mined blocks would be appropriate. So I assume, the program would open a socket connection to some fixed relay node and start accepting the blocks. Could someone show how it could be done. Thank you.

[Edit:] I have since discovered what is probably best suited for the purpose. There is a minimal bitcoin networking stack implemented in python by Dr Christian Decker of ETH Zurich. It was used to gather results for some highly cited research papers on the bitcoin network but at the same time it is extremely readable too.
The easiest way if you come from web development and or you want to put a system in production is to use the most stable and updated implementation/API of Bitcoin Core

note: after downloading it it's best practice to check the md5/sha of the file you downloaded on bitcoin.org to be sure your installer is genuine



1) Install Bitcoin Core 

2) Use it's CLI or JSON rpc APIs: https://en.bitcoin.it/wiki/Original_Bitcoin_client/API_calls_list

there's no step 3!



This in the case your target is to run an app connected to most of the updated nodes, have the latest code with security fixes to at least sign and broadcast transactions, and obviously, query the blockchain!

glhf