For later optimizations, see http://normanmaurer.me/presentations/2014-facebook-eng-netty/slides.html
Simple electrum wallet
Simple electrum wallet
Typical workflow:
client ---- header update ----> wallet client ---- status update ----> wallet client <--- ask history ----- wallet client ---- history ----> wallet client <--- ask tx ----- wallet client ---- tx ----> wallet
block hash
difficulty target for the next block