Network communication basic kit -- IPv4 socket structure

1. Network communication solves three problems

2.ipv4 Socket structure

strcut sockaddr Many network programming functions were born before IPv4 agreement , At that time, they all used sockaddr Structure , For forward compatibility , Now? sockaddr Degenerated into （void *） The role of , Pass an address to the function , As for this function is sockaddr_in still sockaddr_in6, Determined by the address family , Then the internal function forces the type to be converted to the required address type .

General socket structure

struct sockaddr {
    
	sa_family_t sa_family; 		/* address family, AF_xxx */
	char sa_data[14];			/* 14 bytes of protocol address */
};