used sendfile/transmitfile to transmit files over network

.gitignore

common/cpp/src/system_io/system_io.cpp

common/cpp/src/system_io/system_io_linux_mac.cpp

common/cpp/src/system_io/system_io_windows.cpp

receiver/src/request_handler_authorize.cpp

receiver/src/request_handler_db.cpp

.../automatic/full_chain/simple_chain_filegen/check_linux.sh

...c/system_io/ip_tcp_network/client_serv/ip_tcp_network.cpp