一个c++获取ip的简单例子

直接上代码：

// GetLocalIP.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"

/* 编译环境: visual c++ */
#include <stdio.h>
#include <winsock2.h>
#pragma comment(lib,"ws2_32.lib")

int doit(int, char **)
{
 char host_name[255];
 //获取本地主机名称
 if (gethostname(host_name, sizeof(host_name)) == SOCKET_ERROR) {
  printf("Error %d when getting local host name.\n", WSAGetLastError());
  return 1;
 }
 printf("Host name is: %s\n", host_name);

 //从主机名数据库中得到对应的“主机”
 struct hostent *phe = gethostbyname(host_name);
 if (phe == 0) {
  printf("Yow! Bad host lookup.");
  return 1;
 }

 //循环得出本地机器所有IP地址
 for (int i = 0; phe->h_addr_list[i] != 0; ++i) {
  struct in_addr addr;
  memcpy(&addr, phe->h_addr_list[i], sizeof(struct in_addr));
  printf("Address %d : %s\n" , i, inet_ntoa(addr));
  unsigned long lip = inet_addr(inet_ntoa(addr));
  printf("long ip %d =", lip);
 }

 return 0;
}

int _tmain(int argc, _TCHAR* argv[])
{
 WSAData wsaData;
 if (WSAStartup(MAKEWORD(1, 1), &wsaData) != 0) {
  return 255;
 }

 int retval = doit(argc, 0);

 WSACleanup();

 return retval;
}

 

 

linux：

编程获取IP地址大约有以下三种思路：
1. 通过gethostname()和gethostbyname()

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

int main() {
    char hname[128];
    struct hostent *hent;
    int i;

    gethostname(hname, sizeof(hname));

    //hent = gethostent();
    hent = gethostbyname(hname);

    printf("hostname: %s/naddress list: ", hent->h_name);
    for(i = 0; hent->h_addr_list[i]; i++) {
        printf("%s/t", inet_ntoa(*(struct in_addr*)(hent->h_addr_list[i])));
    }
    return 0;
}

运行：
[whb@jcwkyl c]$ ./local_ip
hostname: jcwkyl.jlu.edu.cn
address list: 10.60.56.90      


2. 通过枚举网卡，API接口可查看man 7 netdevice

/*代码来自StackOverflow: http://stackoverflow.com/questions/212528/linux-c-get-the-ip-address-of-local-computer */
#include <stdio.h>     
#include <sys/types.h>
#include <ifaddrs.h>
#include <netinet/in.h>
#include <string.h>
#include <arpa/inet.h>

int main (int argc, const char * argv[]) {
    struct ifaddrs * ifAddrStruct=NULL;
    void * tmpAddrPtr=NULL;

    getifaddrs(&ifAddrStruct);

    while (ifAddrStruct!=NULL) {
        if (ifAddrStruct->ifa_addr->sa_family==AF_INET) { // check it is IP4
            // is a valid IP4 Address
            tmpAddrPtr=&((struct sockaddr_in *)ifAddrStruct->ifa_addr)->sin_addr;
            char addressBuffer[INET_ADDRSTRLEN];
            inet_ntop(AF_INET, tmpAddrPtr, addressBuffer, INET_ADDRSTRLEN);
            printf("%s IP Address %s/n", ifAddrStruct->ifa_name, addressBuffer);
        } else if (ifAddrStruct->ifa_addr->sa_family==AF_INET6) { // check it is IP6
            // is a valid IP6 Address
            tmpAddrPtr=&((struct sockaddr_in *)ifAddrStruct->ifa_addr)->sin_addr;
            char addressBuffer[INET6_ADDRSTRLEN];
            inet_ntop(AF_INET6, tmpAddrPtr, addressBuffer, INET6_ADDRSTRLEN);
            printf("%s IP Address %s/n", ifAddrStruct->ifa_name, addressBuffer);
        }
        ifAddrStruct=ifAddrStruct->ifa_next;
    }
    return 0;
}

运行 ：
[whb@jcwkyl c]$ ./local_ip2
lo IP Address 127.0.0.1
eth0 IP Address 10.60.56.90
eth0:1 IP Address 192.168.1.3
lo IP Address ::
eth0 IP Address ::2001:da8:b000:6213:20f:1fff
eth0 IP Address 0:0:fe80::20f:1fff

3. 打开一个对外界服务器的网络连接，通过getsockname()反查自己的IP