The APIs for the standard networking calls such as socket(), recv() and so on, are in header files relative to the top-level include directory, within the standard subdirectories as conventionally found in /usr/include. For example:
install/include/arpa/tftp.h install/include/netinet/tcpip.h install/include/sys/socket.h install/include/sys/socketvar.h install/include/sys/sockio.h |