第11章 名字与地址转换

#include <netdb.h>

const char *hstrerror(int err);  //全局h_errno被设置错误信息

struct hostent
{
char  *h_name;       //地址的正式名称
char **h_aliases;    //地址的预备名称的指针
int    h_addrtype;   //地址类型
int    h_length;     //地址的比特长度
char **h_addr_list;  //主机网络地址指针,网络字节顺序
};
struct hostent *gethostbyname(const char *hostname);
struct hostent *gethostbyname_r(const char *hostname, struct hostent *result, char *buf, int buflen/*8192*/, int *h_errnop);
struct hostent *gethostbyaddr(const char *addr, socklen_t len, int family);
struct hostent *gethostbyaddr_r(const char *addr, int len, int type, struct hostent *result, char* buf, int buflen/*8192*/, int* h_errnop);

struct servent 
{
char  *s_name;     //正规的服务名
char **s_aliases;  //一个以空指针结尾的可选服务名队列
int    s_port;     //连接该服务时需要用到的端口号，返回的端口号是以网络字节顺序排列的
char  *s_proto;    //连接该服务时用到的协议名
};
struct servent* getservbyname(const char *servname, const char *protoname);
struct servent* getservbyport(int port, const char* protoname);

struct addrinfo 
{
    int ai_flags;      /*in*/
    int ai_family;     /*in*/
    int ai_socktype;   /*in*/
    int ai_protocol;   /*in*/ /*IPPROTO_TCP/IPPROTO_UDP*/
    socklen_t ai_addrlen;
    struct sockaddr *ai_addr;
    char *ai_canonname;
    struct addrinfo *ai_next;
};
int getaddrinfo(const char *hostname, const char *service, const struct addrinfo *hints, struct addrinfo **result);
const char* gai_strerror(int error);     //getaddrinfo的返回值做参数
void freeaddrinfo(struct addrinfo* ai);  //形参是链表头
int getnameinfo(const struct sockaddr* sockaddr, socklen_t addrlen, char* host, socklen_t hostlen, char* serv, socklen_t servlen, int flags);