libevent学习笔记二：使用evdns_getaddrinfo()的例子

来源：互联网发布：施工动画什么软件编辑：程序博客网时间：2024/06/10 12:20
#include<event2/dns.h>#include<event2/util.h>#include<event2/event.h>#include<sys/socket.h>#include<stdio.h>#include<stdlib.h>#include<string.h>#include<assert.h>int n_pending_requests=0;struct event_base* base=NULL;struct user_data{char* name;int idx;};void callback(int errcode,struct evutil_addrinfo* addr,void *ptr){struct user_data* data=(struct user_data* )ptr;const char *name=data->name;if(errcode){printf("%d.%s->%s\n",data->idx,name,evutil_gai_strerror(errcode));}else{struct evutil_addrinfo *ai;printf("%d.%s",data->idx,name);if(addr->ai_canonname){printf("[%s]",addr->ai_canonname);}puts("");for(ai=(evutil_addrinfo*)addr;ai;ai=(evutil_addrinfo*)ai->ai_canonname){char buf[128];const char * s=NULL;if(ai->ai_family==AF_INET){struct sockaddr_in* sin=(struct sockaddr_in*)ai->ai_addr;s=evutil_inet_ntop(AF_INET,&sin->sin_addr,buf,128);}else if(ai->ai_family==AF_INET6){struct sockaddr_in6 *sin6=(struct sockaddr_in6*)ai->ai_addr;s=evutil_inet_ntop(AF_INET6,&sin6->sin6_addr,buf,128);}if(s){printf("   ->%s\n",s);}}evutil_freeaddrinfo(addr);}free(data->name);free(data);if(--n_pending_requests==0){event_base_loopexit(base,NULL);}}int main(int argc,char* argv[]){int i;struct evdns_base* dnsbase;if(argc==1){puts("No addresses given.");return 0;}base=event_base_new();if(!base){return 1;}dnsbase=evdns_base_new(base,1);if(!dnsbase){return 2;}for(i=1;i<argc;++i){struct evutil_addrinfo hints;struct evdns_getaddrinfo_request* req;struct user_data* user_data;memset(&hints,0,sizeof(hints));hints.ai_family=AF_UNSPEC;hints.ai_flags=EVUTIL_AI_CANONNAME;hints.ai_socktype=SOCK_STREAM;hints.ai_protocol=IPPROTO_TCP;if(!(user_data=(struct user_data*)malloc(sizeof(user_data)))){perror("malloc");exit(1);}if(!(user_data->name=strdup(argv[i]))){perror("strdup");exit(1);}user_data->idx=i;++n_pending_requests;req=evdns_getaddrinfo(dnsbase,argv[i],NULL,&hints,callback,user_data);if(req==NULL){printf("    [request for %s returned immediately]\n",argv[i]);}}if(n_pending_requests){event_base_dispatch(base);}evdns_base_free(dnsbase,0);event_base_free(base);return 0;}
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