UNP_1_Chapter 3__基本socket
进程->内核，传递socket地址的函数：bind、connect、sendto
进程<-内核，传递socket地址的函数：accept、recvfrom、getsockname、getpeername
//使用前置0，好习惯bzero(x,sizeof(struct sockaddr_in));struct sockaddr_in{ uint8_t sin_len; //不一定有 sa_family_t sin_family; //不一定有 in_port_t sin_port; struct in_addr sin_addr; unsigned char sin_zero[8];};typedef uint32_t in_addr_t;struct in_addr{ in_addr_t s_addr;};//struct sockaddr{ uint8_t sa_len; sa_family_t sa_family; char sa_data[14];};