getaddrinfo 函数的使用-优快云博客

#include<stdio.h>
#include<sys/socket.h>
#include<netdb.h>
#include<sys/types.h>
#include<strings.h>

void print_family(struct addrinfo *aip)
{
printf(" family ");
switch (aip->ai_family) {
case AF_INET:
  printf("inet");
  break;
case AF_INET6:
  printf("inet6");
  break;
case AF_UNIX:
  printf("unix");
  break;
case AF_UNSPEC:
  printf("unspecified");
  break;
default:
  printf("unknown");
}
}

void print_type(struct addrinfo *aip)
{
printf(" type ");
switch (aip->ai_socktype) {
case SOCK_STREAM:
  printf("stream");
  break;
case SOCK_DGRAM:
  printf("datagram");
  break;
case SOCK_SEQPACKET:
  printf("seqpacket");
  break;
case SOCK_RAW:
  printf("raw");
  break;
default:
  printf("unknown (%d)", aip->ai_socktype);
}
}

void print_protocol(struct addrinfo *aip)
{
printf(" protocol ");
switch (aip->ai_protocol) {
case 0:
  printf("default");
  break;
case IPPROTO_TCP:
  printf("TCP");
  break;
case IPPROTO_UDP:
  printf("UDP");
  break;
case IPPROTO_RAW:
  printf("raw");
  break;
default:
  printf("unknown (%d)", aip->ai_protocol);
}
}

void print_flags(struct addrinfo *aip)
{
printf("flags");
if (aip->ai_flags == 0) {
  printf(" 0");
} else {
  if (aip->ai_flags & AI_PASSIVE)
   printf(" passive");
  if (aip->ai_flags & AI_CANONNAME)
   printf(" canon");
  if (aip->ai_flags & AI_NUMERICHOST)
   printf(" numhost");
}
}

int main(int argc,char **argv){
struct addrinfo *ailist,*aip;
struct addrinfo hint;
struct sockaddr_in *sinp;
const char *addr;
int err;
//inet_addrstrlen用来存放足够长的ipv4的地址字符串如a.b.c.d点分十进制的ip地址
char abuf[INET_ADDRSTRLEN];
if(argc !=3 && argc !=2){
  return -1;
}
//将结构体清零
bzero(&hint,sizeof(struct addrinfo));
hint.ai_flags=AI_CANONNAME;
//调用getaddrinfo得到信息
err=getaddrinfo(argv[1],(argc==2)?NULL:argv[2],&hint,&ailist);
if(err){
  printf("getaddrinfo error: %s",gai_strerror(err));
return -1;
}
for(aip=ailist;aip!=NULL;aip=aip->ai_next){
print_flags(aip);
print_family(aip);
print_type(aip);
print_protocol(aip);
if(aip->ai_family==AF_INET){
  sinp=(struct sockaddr_in *)aip->ai_addr;
  addr=inet_ntop(AF_INET,&sinp->sin_addr,abuf,INET_ADDRSTRLEN);
  printf("abuf: %s",abuf);
  printf("address: %s",addr?addr:"UNKNOWN");
  printf("port %d",ntohs(sinp->sin_port));
}
printf("\n");
}