sockaddr_in address structure of the AF_INET address family

With the AF_INET address family, a name comprises a 4-byte Internet address and a port number. You use the sockaddr_in address structure for the AF_INET address family. This structure has a variant for #define SIN_LEN.

The sockaddr_in structure is declared in the <netinet.in.h> header as follows:

struct sockaddr_in {
   short            sin_family;      /* address family AF_INET */
   u_short          sin_port;        /* 16-bit port number */
   struct in_addr   sin_addr;        /* 32-bit Internet address */
   char             sin_zero[8];
   };

Structure variant of sockaddr_in with #define SIN_LEN set to support BSD 4.4 systems:

struct sockaddr_in {
   u_char           sin_len;         /* structure length */
   u_char           sin_family;      /* address family AF_INET */
   u_short          sin_port;        /* 16 bit port number */
   struct in_addr   sin_addr;        /* 32 bit Internet address */
   char             sin_zero[8];
   };

You can supply a variable server of type struct sockaddr_in with a name by using the following statements:

struct sockaddr_in server;
...
server.sin_family = AF_INET;
server.sin_port = htons(8888);
server.sin_addr.s_addr = htonl(INADDR_ANY);

A pointer to the variable server can now be passed as the current parameter, e.g. with a bind() call, to bind the name to a socket:

bind(..., &server, ...) /* bind() call with type conversion */

The structures for host, protocol and service names are described in the chapter “Address conversion with SOCKETS(BS2000)”.