#include <netdb.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <arpa/inet.h> #include <netinet/in.h> #include <sys/socket.h> typedef enum {false,true}bool; int main() {     bool flag;     int    sock;     char **pptr = NULL;     struct sockaddr_in    destAddr;     struct hostent    *ptr = NULL;     char destIP[128];     char szBuffer[] = {"GET /ip2city.asp HTTP/1.1\r\nHost:www.ip138.com\r\nConnection:Close\r\n\r\n"};     char res[1024]; 　　//初始化socket     sock = socket(AF_INET,SOCK_STREAM,0);     if( -1 == sock ){         perror("creat socket failed");         exit(0);     }     bzero((void *)&destAddr,sizeof(destAddr));     destAddr.sin_family = AF_INET;            destAddr.sin_port = htons(80);  　　//首先是获取www.ip138.com的IP地址     ptr = gethostbyname("www.ip138.com");     if(NULL == ptr){         perror("gethostbyname error");         exit(0);     }   　　//对于www.ip138.com的每个IP进行尝试连接，直到有一个连接成功为止，或者无法连接，则退出程序     for(flag=false,pptr=ptr->h_addr_list ; NULL != *pptr ; ++pptr){         inet_ntop(ptr->h_addrtype,*pptr,destIP,sizeof(destIP));         printf("addr:%s\n",destIP);         destAddr.sin_addr.s_addr = inet_addr(destIP);         if(-1!=connect(sock,(struct sockaddr *)&destAddr,sizeof(struct sockaddr))){             flag = true;             break;         }     }     if(false == flag){         perror("connect failed");     } 　　//发送获取IP的数据包给www.ip138.com     if(strlen(szBuffer) != send(sock,szBuffer,strlen(szBuffer),0)){         perror("send error");         exit(0);     } 　　//接收数据包     if(-1 == recv(sock,res,1024,0)){         perror("recv error");         exit(0);     }     printf("res:\n%s\n",res);        return 0; }

gcc -o getip getip.c

./getip