hostent
#include
#include
/* Description of data base entry for a single host. */ struct hostent { char *h_name; /* Official name of host. */ char **h_aliases; /* Alias list. */ int h_addrtype; /* Host address type. */ int h_length; /* Length of address. */ char **h_addr_list; /* List of addresses from name server. */ #define h_addr h_addr_list[0] /* Address, for backward compatibility. */ };
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sockaddr and sockaddr_in
#include
struct sockaddr_in { short int sin_family; /* Address family */ unsigned short int sin_port; /* Port number */ struct in_addr sin_addr; /* Internet address */ unsigned char sin_zero[8]; /* Same size as struct sockaddr */ };
struct sockaddr { unsigned short sa_family; /* address family, AF_xxx */ char sa_data[14]; /* 14 bytes of protocol address */ };
struct in_addr { unsigned long s_addr; };
typedef struct in_addr { union { struct{ unsigned char s_b1, s_b2, s_b3, s_b4; } S_un_b; struct { unsigned short s_w1, s_w2; } S_un_w; unsigned long S_addr; } S_un; } IN_ADDR;
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sin_family指代协议族,在socket编程中选AF_INET
sin_port存储端口号(使用网络字节顺序)
sin_addr存储IP地址,使用in_addr这个数据结构
sin_zero是为了让sockaddr与sockaddr_in两个数据结构保持大小相同而保留的空字节。
s_addr按照网络字节顺序存储IP地址
sockaddr_in和sockaddr是并列的结构,指向sockaddr_in的结构体的指针也可以指向
sockadd的结构体,并代替它。也就是说,你可以使用sockaddr_in建立你所需要的信息,
在最后用进行类型转换就可以了
bzero((char*)&sockfd,sizeof(mysock));//初始化
sockfd结构体名
sockfd.sa_family=AF_INET;
socdfd.sin_addr.s_addr=inet_addr("192.168.0.1");
……
等到要做转换的时候用:
(struct sockaddr*)sockfd
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