include <netinet/in.h> 
 
struct sockaddr { 
  unsigned short  sa_family;  // 2 bytes address family, AF_xxx 
  char       sa_data[14];   // 14 bytes of protocol address 
}; 
 
// IPv4 AF_INET sockets: 
 
struct sockaddr_in { 
  short      sin_family;    // 2 bytes e.g. AF_INET, AF_INET6 
  unsigned short  sin_port;  // 2 bytes e.g. htons(3490) 
  struct in_addr  sin_addr;   // 4 bytes see struct in_addr, below 
  char       sin_zero[8];   // 8 bytes zero this if you want to 
}; 
 
struct in_addr { 
  unsigned long s_addr;     // 4 bytes load with inet_pton() 
}; 

int sockfd; 
struct sockaddr_in servaddr; 
 
sockfd = Socket(AF_INET, SOCK_STREAM, 0); 
 
/* 填充struct sockaddr_in */ 
bzero(&servaddr, sizeof(servaddr)); 
servaddr.sin_family = AF_INET; 
servaddr.sin_port = htons(SERV_PORT); 
inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr); 
 
/* 强制转换成struct sockaddr */ 
connect(sockfd, (struct sockaddr *) &servaddr, sizeof(servaddr));