Socket programming 1

 1 struct addrinfo {

 2     int              ai_flags;     // AI_PASSIVE, AI_CANONNAME, etc.

 3     int              ai_family;    // AF_INET, AF_INET6, AF_UNSPEC

 4     int              ai_socktype;  // SOCK_STREAM, SOCK_DGRAM

 5     int              ai_protocol;  // use 0 for "any"

 6     size_t           ai_addrlen;   // size of ai_addr in bytes

 7     struct sockaddr *ai_addr;      // struct sockaddr_in or _in6

 8     char            *ai_canonname; // full canonical hostname

 9     struct addrinfo *ai_next;      // linked list, next node

 };

 

  

AI_PASSIVE 表示用自己的IP地址。

AF_INET 表示用ipv, AF_INET6表示用ipv6， AF_UNSPEC表示不确定是ipv4还是ipv6

SOCK_STREAM 表示TCP， SOCK_DGRAM 表示UDP

 1 struct sockaddr {
 2     unsigned short sa_family;   // address family, AF_xxx
 3     char           sa_data[14]; // 14 bytes of protocol address
 4 };
 5 
 6 // (IPv4 only--see struct sockaddr_in6 for IPv6)
 7 struct sockaddr_in {
 8     short int          sin_family;  // Address family, AF_INET
 9     unsigned short int sin_port;    // Port number
10     struct in_addr     sin_addr;    // Internet address
11     unsigned char      sin_zero[8]; // Same size as struct sockaddr
12 };
13 
14 // (IPv4 only--see struct in6_addr for IPv6)
15 // Internet address (a structure for historical reasons)
16 struct in_addr {
17     uint32_t s_addr; // that's a 32-bit int (4 bytes)
18 };
19 
20 // (IPv6 only--see struct sockaddr_in and struct in_addr for IPv4)
21 struct sockaddr_in6 {
22     u_int16_t       sin6_family;   // address family, AF_INET6
23     u_int16_t       sin6_port;     // port number, Network Byte Order
24     u_int32_t       sin6_flowinfo; // IPv6 flow information
25     struct in6_addr sin6_addr;     // IPv6 address
26     u_int32_t       sin6_scope_id; // Scope ID
27 };
28 
29 struct in6_addr {
30     unsigned char s6_addr[16]; // IPv6 address
31 };

sockaddr和sockaddr_in是一回事，可以相互cast，由于历史原因sockaddr_in里面有in_addr，in_addr保存的就是ip地址

 struct sockaddr_in sa; // IPv4
2 struct sockaddr_in6 sa6; // IPv6
3 inet_pton(AF_INET, "192.0.2.1", &(sa.sin_addr)); // IPv4
4 inet_pton(AF_INET6, "2001:db8:63b3:1::3490", &(sa6.sin6_addr)); // IPv6
5 

inet_pton用于把ip转换成int形式，inet_addr已经不推荐使用了。

 inet_ntop(AF_INET, &(sa.sin_addr), ip4, INET_ADDRSTRLEN);
2 printf("The IPv4 address is: %s\n", ip4);
3 // IPv6:
4 char ip6[INET6_ADDRSTRLEN]; // space to hold the IPv6 string
5 struct sockaddr_in6 sa6;    // pretend this is loaded with something
6 inet_ntop(AF_INET6, &(sa6.sin6_addr), ip6, INET6_ADDRSTRLEN);
7 printf("The address is: %s\n", ip6);
8 

inet_ntop把int形式转换成dot形式。

 1 int main(int argc, char *argv[])
 2 {
 3     struct addrinfo hints, *res, *p;
 4     int status;
 5     char ipstr[INET6_ADDRSTRLEN];
 6     if (argc != 2) {
 7         fprintf(stderr,"usage: showip hostname\n");
 8         return 1;
 9     }
10     memset(&hints, 0, sizeof hints);
11     hints.ai_family = AF_UNSPEC; // AF_INET or AF_INET6 to force version
12     hints.ai_socktype = SOCK_STREAM;
13     if ((status = getaddrinfo(argv[1], NULL, &hints, &res)) != 0) {
14         fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(status));
15         return 2;
16     }
17     printf("IP addresses for %s:\n\n", argv[1]);
18     for(p = res;p != NULL; p = p->ai_next) {
19         void *addr;
20         char *ipver;
21         // get the pointer to the address itself,
22         // different fields in IPv4 and IPv6:
23         if (p->ai_family == AF_INET) { // IPv4
24             struct sockaddr_in *ipv4 = (struct sockaddr_in *)p->ai_addr;
25             addr = &(ipv4->sin_addr);
26             ipver = "IPv4";
27         } else { // IPv6
28             struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)p->ai_addr;
29             addr = &(ipv6->sin6_addr);
30             ipver = "IPv6";
31         }
32         // convert the IP to a string and print it:
33         inet_ntop(p->ai_family, addr, ipstr, sizeof ipstr);
34         printf(" %s: %s\n", ipver, ipstr);
35     }
36     freeaddrinfo(res); // free the linked list
37     return 0;
38 }
39 
 int getaddrinfo(const char *node,     // e.g. "www.example.com" or IP
2                 const char *service, // e.g. "http" or port number
3                 const struct addrinfo *hints,
4                 struct addrinfo **res);
5 

 

getaddrinfo自动填充hints，然后赋值给res，取代了gethostbyname之类。

 

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

// (IPv4 only--see struct sockaddr_in6 for IPv6)
struct sockaddr_in {
    short int          sin_family;  // Address family, AF_INET
    unsigned short int sin_port;    // Port number
    struct in_addr     sin_addr;    // Internet address
    unsigned char      sin_zero[8]; // Same size as struct sockaddr
};

// (IPv4 only--see struct in6_addr for IPv6)
// Internet address (a structure for historical reasons)
struct in_addr {
    uint32_t s_addr; // that's a 32-bit int (4 bytes)
};

// (IPv6 only--see struct sockaddr_in and struct in_addr for IPv4)
struct sockaddr_in6 {
    u_int16_t       sin6_family;   // address family, AF_INET6
    u_int16_t       sin6_port;     // port number, Network Byte Order
    u_int32_t       sin6_flowinfo; // IPv6 flow information
    struct in6_addr sin6_addr;     // IPv6 address
    u_int32_t       sin6_scope_id; // Scope ID
};

struct in6_addr {
    unsigned char s6_addr[16]; // IPv6 address
};