前言

下面列舉多種方法獲取本地IP,這些方法在linux系統下均可執行,有些方法亦可以在Windows和Android下執行.

原始碼

/*下列幾種方法均優先輸出非迴環IP:127.0.0.1 
inet_ntoa(): 系統函式,將網路的二進位制數IP轉化成點分十進位制IP
inet_ntop(): 系統函式,新型函式,作用與inet_ntoa()相似

inet_aton(): 系統函式,將點分十進位制IP轉化成網路的二進位制數IP
inet_pton(): 系統函式,新型函式,inet_aton()相似
*/

#include <stdlib.h>
#include <stdio.h>
 

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

//使用 ifconf結構體和ioctl函式時需要用到該標頭檔案
#include <net/if.h>
#include <sys/ioctl.h>

//使用ifaddrs結構體時需要用到該標頭檔案
#include <ifaddrs.h>


#define PJ_MAX_HOSTNAME  (128)
 


#define RUN_SUCCESS 0
#define RUN_FAIL -1

/* 該方法一般取出的ip為 127.0.0.1 ,windows也可以使用此類方法,但是需要略為改動*/
int get_local_ip_using_hostname(char *str_ip) 
{
    int status = RUN_FAIL;
    int i = 0;
    char buf[PJ_MAX_HOSTNAME] = {0};
    char *local_ip = NULL;
    if (gethostname(buf, sizeof(buf)) == 0)
    {
        struct
 
 hostent *temp_he;
        temp_he = gethostbyname(buf);
        if (temp_he) 
        {
            for(i = 0; temp_he->h_addr_list[i]; i++)
            {
                local_ip = NULL;
                local_ip = inet_ntoa(*(struct in_addr *)(temp_he->h_addr_list[i]));
                if(local_ip)
                {
                    strcpy(str_ip, local_ip);
                    status = RUN_SUCCESS;
                    if(strcmp("127.0.0.1", str_ip))
                    {
                        break;
                    }
                }
            }
        }
    }
    return status;
}


/*該方法需要能夠夠ping通 1.1.1.1(DNS伺服器IP) , 而且該伺服器 53 埠是開著的
(也可以用一個能夠connect的遠端伺服器IP代替),windows也可以使用此類方法,但是需要略為改動*/
int get_local_ip_using_create_socket(char *str_ip) 
{
    int status = RUN_FAIL;
    int af = AF_INET;
    int sock_fd = socket(AF_INET, SOCK_DGRAM, 0);
    struct sockaddr_in remote_addr;
    struct sockaddr_in local_addr;
    char *local_ip = NULL;
    socklen_t len = 0;

    remote_addr.sin_family = AF_INET;
    remote_addr.sin_port = htons(53);
    remote_addr.sin_addr.s_addr = inet_addr("1.1.1.1");

    len =  sizeof(struct sockaddr_in);
    status = connect(sock_fd, (struct sockaddr*)&remote_addr, len);
    if(status != 0 ){
        printf("connect err \n");
    }

    len =  sizeof(struct sockaddr_in);
    getsockname(sock_fd, (struct sockaddr*)&local_addr, &len);

    local_ip = inet_ntoa(local_addr.sin_addr);
    if(local_ip)
    {
        strcpy(str_ip, local_ip);
        status = RUN_SUCCESS;
    }
    return status;
}

/*linux上支援（Android上也支援）， 此函式不僅能獲取IP，還可以獲取MAC地址、掩碼和廣播地址等*/
int get_local_ip_using_ifconf(char *str_ip)  
{
    int sock_fd, intrface;
    struct ifreq buf[INET_ADDRSTRLEN];
    struct ifconf ifc;
    char *local_ip = NULL;
    int status = RUN_FAIL;

    if ((sock_fd = socket(AF_INET, SOCK_DGRAM, 0)) >= 0)
    {
        ifc.ifc_len = sizeof(buf);
        ifc.ifc_buf = (caddr_t)buf;
        if (!ioctl(sock_fd, SIOCGIFCONF, (char *)&ifc))
        {
            intrface = ifc.ifc_len/sizeof(struct ifreq);
            while (intrface-- > 0)
            {
                if (!(ioctl(sock_fd, SIOCGIFADDR, (char *)&buf[intrface])))
                {
                    local_ip = NULL;
                    local_ip = inet_ntoa(((struct sockaddr_in*)(&buf[intrface].ifr_addr))->sin_addr);
                    if(local_ip)
                    {
                        strcpy(str_ip, local_ip);
                        status = RUN_SUCCESS;
                        if(strcmp("127.0.0.1", str_ip))
                        {
                            break;
                        }
                    }

                }
            }
        }
        close(sock_fd);
    }
    return status;
}

/*可以檢測ip4也可以檢測ip6，但是需要ifaddrs.h，某些Android系統上沒有該標頭檔案（可自己實現該標頭檔案所帶內容）
該方法較為強大，可以通過網絡卡名（ifAddrStruct->ifr_name）獲取IP. 
*/
int get_local_ip_using_ifaddrs(char *str_ip)
{
    struct ifaddrs * ifAddrStruct=NULL;
    void * tmpAddrPtr=NULL;
    int status = RUN_FAIL;

    getifaddrs(&ifAddrStruct);

    while (ifAddrStruct!=NULL) 
    {
        if (ifAddrStruct->ifa_addr->sa_family==AF_INET)  // check it is IP4
        { 
            tmpAddrPtr = &((struct sockaddr_in *)ifAddrStruct->ifa_addr)->sin_addr;
            if(inet_ntop(AF_INET, tmpAddrPtr, str_ip, INET_ADDRSTRLEN))
            {
                status = RUN_SUCCESS;
                if(strcmp("127.0.0.1",str_ip))
                {
                     break;
                }
            }  
        }else if(ifAddrStruct->ifa_addr->sa_family==AF_INET6){
            //可以新增IP6相應程式碼
        }
        ifAddrStruct=ifAddrStruct->ifa_next;
    }
    return status;
}

/*使用命令獲取IP,此首要條件是需要系統支援相關命令,限制性條件較多,下面該方法是獲取本機的ip地址*/
int get_netway_ip_using_res(char *str_ip)
{
    int status = RUN_FAIL;
    char do_comment[] = "ifconfig | grep 'inet addr' | awk '{print $2}' | sed 's/.*://g'"; 
    //該命令是從ifconfig中提取相應的IP
    FILE *fp = NULL;
    fp = popen(do_comment, "r");
    if(fp != NULL)
    {
        status = RUN_SUCCESS;
        while( !feof(fp) )
        {
            fgets(str_ip, 1024, fp);
            status = RUN_SUCCESS;
            if(strcmp("127.0.0.1", str_ip))
            {
                break;
            }
        }   
    }
    fclose(fp); 
    return status;
}

int main()
{
    char local_ip1[INET_ADDRSTRLEN] = {0};
    char local_ip2[INET_ADDRSTRLEN] = {0};
    char local_ip3[INET_ADDRSTRLEN] = {0};
    char local_ip4[INET_ADDRSTRLEN] = {0};
    char local_ip5[INET_ADDRSTRLEN] = {0};

    if( get_local_ip_using_hostname(local_ip1) ==  RUN_SUCCESS)
    {
        printf("get_local_ip_using_hostname() get local ip : %s \n", local_ip1);
    }else{
        printf("get_local_ip_using_hostname() err \n");
    }

    if( get_local_ip_using_create_socket(local_ip2) == RUN_SUCCESS)
    {
        printf("get_local_ip_using_socket() get local ip : %s \n", local_ip2);
    }else{
        printf("get_local_ip_using_socket() err \n");
    }

    if( get_local_ip_using_ifconf(local_ip3) == RUN_SUCCESS)
    {
        printf("get_local_ip_using_ifconf() get local ip : %s \n", local_ip3);
    }else{
        printf("get_local_ip_using_ifconf() err \n");
    }

    if( get_local_ip_using_ifaddrs(local_ip4) == RUN_SUCCESS)
    {
        printf("get_local_ip_using_ifaddrs() get local ip : %s \n", local_ip4);
    }else{
        printf("get_local_ip_using_ifaddrs() err \n");
    }

    if( get_netway_ip_using_res(local_ip5) == RUN_SUCCESS)
    {
        printf("get_netway_ip_using_res() get local ip : %s \n", local_ip5);
    }else{
        printf("get_netway_ip_using_res() err \n");
    }

    return 0;
}

執行結果: