What files, libraries, classes, blocks of code used for TCP/IP connection, peer discovery, HTTP connection, UDP connection in bitcoin core (0.1.5 and latest releases including last 0.18.0), other c/c++-based wallets, cgminer (first 0.1 and latest releases 4.11.1), bfgminer (first 0.1 and latest releases 5.5.0)? How network programming done in bitcoin software? How programmed server, client, peers? And on what programming and software standards, specifications (RFC, ISO, other) is based this network communications and programming? Please, be more specific and concrete, better with source code examples.