C语言获取本地IP(适用于多种操作系统)

#前言

下面列举多种方法获取本地IP,这些方法在linux系统下均可运行,有些方法亦可以在Windows和Android下运行.

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源码

/*下列几种方法均优先输出非回环IP:127.0.0.1 
inet_ntoa(): 系统函数,将网络的二进制数IP转化成点分十进制IP
inet_ntop(): 系统函数,新型函数,作用与inet_ntoa()相似

inet_aton(): 系统函数,将点分十进制IP转化成网络的二进制数IP
inet_pton(): 系统函数,新型函数,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结构体和ioctl函数时需要用到该头文件
#include <net/if.h>
#include <sys/ioctl.h>

//使用ifaddrs结构体时需要用到该头文件
#include <ifaddrs.h>


#define PJ_MAX_HOSTNAME  (128)

#define RUN_SUCCESS 0
#define RUN_FAIL -1

/* 该方法一般取出的ip为 127.0.0.1 ,windows也可以使用此类方法,但是需要略为改动*/
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;
}


/*该方法需要能够够ping通 1.1.1.1(DNS服务器IP) , 而且该服务器 53 端口是开着的
(也可以用一个能够connect的远程服务器IP代替),windows也可以使用此类方法,但是需要略为改动*/
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上支持（Android上也支持）， 此函数不仅能获取IP，还可以获取MAC地址、掩码和广播地址等*/
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;
}

/*可以检测ip4也可以检测ip6，但是需要ifaddrs.h，某些Android系统上没有该头文件（可自己实现该头文件所带内容）
该方法较为强大，可以通过网卡名（ifAddrStruct->ifa_name）获取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){
			//可以添加IP6相应代码
		}
        ifAddrStruct=ifAddrStruct->ifa_next;
    }
	return status;
}

/*使用命令获取IP,此首要条件是需要系统支持相关命令,限制性条件较多,下面该方法是获取本机的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'"; 
	//该命令是从ifconfig中提取相应的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;
}

运行结果: