getaddrinfo()返回环回地址

Question

用于LAN中某些套接字通信应用的目标机器192.168.98.91用于IPv4.

当我尝试用getaddrinfo()解析IPaddress时,它返回 127.0.0.1

我该怎么192.168.98.91办？

我给自己定192.168.98.91了myhost在/etc/hosts文件和ping我因myhost表现192.168.98.91为IP地址.

我的机器是CentOS6.4.

这是/ etc/hosts的设置.

192.168.98.91   myhost
127.0.0.1   myhost localhost.localdomain 

这是我的代码.

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <errno.h>
#include <arpa/inet.h>

int
main(int argc,char *argv[]){
    int sock;
    struct addrinfo hints,*res;
    int n;
    int err;
    if(argc != 2){
        fprintf(stderr,"Usage : %s dst \n",argv[0]);
        return 1;
    } 
    memset(&hints,0,sizeof(hints));
    hints.ai_family = AF_UNSPEC; 
    hints.ai_socktype = SOCK_DGRAM;
    err = getaddrinfo(argv[1],"12345",&hints,&res);
    if(err != 0){
        perror("getaddrinfo");
        printf("getaddrinfo %s\n",strerror(errno));
        printf("getaddrinfo : %s \n",gai_strerror(err));
        return 1;
    }

    sock = socket(res->ai_family,res->ai_socktype,0);
    if(sock < 0){
        perror("socket");
        return 1;
    }
    {
        const char *ipverstr;
        switch (res->ai_family){
            case AF_INET:
                ipverstr = "IPv4";
                break;
            case AF_INET6:
                ipverstr = "IPv6";
                break;
            default:
                ipverstr = "unknown";
                break;            
        }
        printf("ipverstr = %s\n ",ipverstr);            
    }
    n = sendto(sock,"HELLO",5,0,res->ai_addr,res->ai_addrlen);
    //n = sendto(sock,"HELLO", 5, 0,(struct sockaddr *)addr, sizeof(addr));
    if(n<1){
        perror("sendto");
        {

        }
        return 1;
    }
    struct sockaddr_in *addr;
    addr = (struct sockaddr_in *)res->ai_addr; 
    printf("inet_ntoa(in_addr)sin = %s\n",inet_ntoa((struct in_addr)addr->sin_addr));

    printf("############ finish !! #######\n");
    close(sock);
    freeaddrinfo(res);
    return 0;
}

Answer 1

如果你遵循返回的结果链getaddrinfo()使用ai_next的会员struct addrinfo,你想也得到192.168.98.91了myhost.

在这里http://man7.org/linux/man-pages/man3/getaddrinfo.3.html您会找到一个完整的示例,还展示了如何执行此操作:

从上面的链接:

       ...
       s = getaddrinfo(NULL, argv[1], &hints, &result);
       if (s != 0) {
           fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(s));
           exit(EXIT_FAILURE);
       }

       /* getaddrinfo() returns a list of address structures.
          Try each address until we successfully bind(2).
          If socket(2) (or bind(2)) fails, we (close the socket
          and) try the next address. */

       for (rp = result; rp != NULL; rp = rp->ai_next) {
          /* Do something with rp->ai_family, rp->ai_socktype, ... */
       }
       ...

myhost从以下行中删除/etc/hosts:

127.0.0.1   myhost localhost.localdomain 

会导致127.0.0.1不返回getaddrinfo()了询问它的时候myhost.