摘要: 移动或网站开发中经常需要设备或网站内网及外网IP,
     本篇文章讲解如何使用C语言获取外网及内网IP.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <net/ethernet.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <sys/sockio.h>
#include <net/if.h>
#include <errno.h>
#include <net/if_dl.h>

#define min(a,b)    ((a) < (b) ? (a) : (b))
#define max(a,b)    ((a) > (b) ? (a) : (b))
#define MAXADDRS 32
#define BUFFERSIZE  4000

char *if_names[MAXADDRS];
char *ip_names[MAXADDRS];
char *hw_addrs[MAXADDRS];
unsigned long ip_addrs[MAXADDRS];

static int   nextAddr = 0;

/*
 * 获取内网IP
 */

void InitAddresses(){
    int i;
    for (i=0; i<MAXADDRS; ++i)
    {
        if_names[i] = ip_names[i] = hw_addrs[i] = NULL;
        ip_addrs[i] = 0;
    }
}

void FreeAddresses(){
    int i;
    for (i=0; i<MAXADDRS; ++i)
    {
        if (if_names[i] != 0) free(if_names[i]);
        if (ip_names[i] != 0) free(ip_names[i]);
        if (hw_addrs[i] != 0) free(hw_addrs[i]);
        ip_addrs[i] = 0;
    }
    InitAddresses();
}

void GetIPAddresses(){

    int                 i, len, flags;
    char                buffer[BUFFERSIZE], *ptr, lastname[IFNAMSIZ], *cptr;
    struct ifconf       ifc;
    struct ifreq        *ifr, ifrcopy;
    struct sockaddr_in  *sin;

    char temp[80];

    int sockfd;

    for (i=0; i<MAXADDRS; ++i)
    {
        if_names[i] = ip_names[i] = NULL;
        ip_addrs[i] = 0;
    }

    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0)
    {
        perror("socket failed");
        return;
    }

    ifc.ifc_len = BUFFERSIZE;
    ifc.ifc_buf = buffer;

    if (ioctl(sockfd, SIOCGIFCONF, &ifc) < 0)
    {
        perror("ioctl error");
        return;
    }

    lastname[0] = 0;

    for (ptr = buffer; ptr < buffer + ifc.ifc_len; )
    {
        ifr = (struct ifreq *)ptr;
        len = max(sizeof(struct sockaddr), ifr->ifr_addr.sa_len);
        ptr += sizeof(ifr->ifr_name) + len;  // for next one in buffer

        if (ifr->ifr_addr.sa_family != AF_INET)
        {
            continue;   // ignore if not desired address family
        }

        if ((cptr = (char *)strchr(ifr->ifr_name, ':')) != NULL)
        {
            *cptr = 0;      // replace colon will null
        }

        if (strncmp(lastname, ifr->ifr_name, IFNAMSIZ) == 0)
        {
            continue;   /* already processed this interface */
        }

        memcpy(lastname, ifr->ifr_name, IFNAMSIZ);

        ifrcopy = *ifr;
        ioctl(sockfd, SIOCGIFFLAGS, &ifrcopy);
        flags = ifrcopy.ifr_flags;
        if ((flags & IFF_UP) == 0)
        {
            continue;   // ignore if interface not up
        }

        if_names[nextAddr] = (char *)malloc(strlen(ifr->ifr_name)+1);
        if (if_names[nextAddr] == NULL)
        {
            return;
        }
        strcpy(if_names[nextAddr], ifr->ifr_name);

        sin = (struct sockaddr_in *)&ifr->ifr_addr;
        strcpy(temp, inet_ntoa(sin->sin_addr));

        ip_names[nextAddr] = (char *)malloc(strlen(temp)+1);
        if (ip_names[nextAddr] == NULL)
        {
            return;
        }
        strcpy(ip_names[nextAddr], temp);

        ip_addrs[nextAddr] = sin->sin_addr.s_addr;

        ++nextAddr;
    }

    close(sockfd);
}

void GetHWAddresses(){

    struct ifconf ifc;
    struct ifreq *ifr;
    int i, sockfd;
    char buffer[BUFFERSIZE], *cp, *cplim;
    char temp[80];

    for (i=0; i<MAXADDRS; ++i)
    {
        hw_addrs[i] = NULL;
    }

    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0)
    {
        perror("socket failed");
        return;
    }

    ifc.ifc_len = BUFFERSIZE;
    ifc.ifc_buf = buffer;

    if (ioctl(sockfd, SIOCGIFCONF, (char *)&ifc) < 0)
    {
        perror("ioctl error");
        close(sockfd);
        return;
    }

    ifr = ifc.ifc_req;

    cplim = buffer + ifc.ifc_len;

    for (cp=buffer; cp < cplim; )
    {
        ifr = (struct ifreq *)cp;
        if (ifr->ifr_addr.sa_family == AF_LINK)
        {
            struct sockaddr_dl *sdl = (struct sockaddr_dl *)&ifr->ifr_addr;
            int a,b,c,d,e,f;
            int i;

            strcpy(temp, (char *)ether_ntoa(LLADDR(sdl)));
            sscanf(temp, "%x:%x:%x:%x:%x:%x", &a, &b, &c, &d, &e, &f);
            sprintf(temp, "%02X:%02X:%02X:%02X:%02X:%02X",a,b,c,d,e,f);

            for (i=0; i<MAXADDRS; ++i)
            {
                if ((if_names[i] != NULL) && (strcmp(ifr->ifr_name, if_names[i]) == 0))
                {
                    if (hw_addrs[i] == NULL)
                    {
                        hw_addrs[i] = (char *)malloc(strlen(temp)+1);
                        strcpy(hw_addrs[i], temp);
                        break;
                    }
                }
            }
        }
        cp += sizeof(ifr->ifr_name) + max(sizeof(ifr->ifr_addr), ifr->ifr_addr.sa_len);
    }

    close(sockfd);
}

/*
 * 获取外网IP
 */
- (char *)getPublicIPAdressWithHostName:(char *)hostName{

    int    sock;
    char **pptr = NULL;
    struct sockaddr_in    destAddr;
    struct hostent    *ptr = NULL;
    char destIP[128];

    sock = socket(AF_INET,SOCK_STREAM,0);
    if( -1 == sock ){
        perror("creat socket failed");
        return false;
    }
    bzero((void *)&destAddr,sizeof(destAddr));
    destAddr.sin_family = AF_INET;
    destAddr.sin_port = htons(80);
    ptr = gethostbyname(hostName);
    if(NULL == ptr){
        perror("gethostbyname error");
        return false;
    }
    for(pptr=ptr->h_addr_list ; NULL != *pptr ; ++pptr){
        inet_ntop(ptr->h_addrtype,*pptr,destIP,sizeof(destIP));
        printf("addr:%s\n",destIP);
        return destIP;
    }
    return destIP;
}

//返回内网IP的的方法,在需要内网IP的地方直接调用deviceIPAdress方法即可
- (NSString *)deviceIPAdress {

    InitAddresses();
    GetIPAddresses();
    GetHWAddresses();

    return [NSString stringWithFormat:@"%s", ip_names[1]];
}

//同理获取外网IP时直接调用- (char *)getPublicIPAdressWithHostName:(char *)hostName方法即可,例如

[NSString stringWithFormat:@"%s",[self getPublicIPAdressWithHostName:"www.baidu.com"]];-