下面的代码，想半天了，不知道哪出了有关问题。大家帮小弟我看看吧

下面的代码，想半天了，不知道哪出了问题。大家帮我看看吧

C/C++ code

#include <stdio.h>#include <winsock2.h>int main(){    char buff[255];    WSAData wsaData;    WSAStartup(MAKEWORD(2, 2), &wsaData);    hostent * hostaddr,*tmp;          gethostname(buff, sizeof(buff));    hostaddr=gethostbyname(buff);        printf("Host name is: %s\n", buff);     printf("ip:%s\n",inet_ntoa(*(struct in_addr *)hostaddr->h_addr));        while (1)     {    tmp = gethostbyname(buff);        if (inet_ntoa(*(struct in_addr *)hostaddr->h_addr) == inet_ntoa(*(struct in_addr *)tmp->h_addr))             puts("ip 未改变");        else             printf("ip 改变为:%s\n",inet_ntoa(*(struct in_addr *)tmp->h_addr));         Sleep(3000);    }            WSACleanup();    return 0;}

//本机ip:192.168.0.1
//运行本程序后 我把本机ip改为 192.168.0.2 后 
//程序不打印更改后的 ip

哪个地方出问题了 我这样做比较 不行吗？ 有什么号的方法比较 两次gethostbyname(buff); 获得的
地址差异。




[解决办法]
inet_ntoa 这个明显返回的是一个字符串指针。
这样比较的是地址，应该比较内容才对。
strstr比较或者直接一个个字符比较过去。
[解决办法]
inet_ntoa返回的是指针啊，你比较的是返回的指针的地址当然不可以。
[解决办法]
h_addr如果这个成员时字符串或者字符数组类型那么用strcmp比较
[解决办法]

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h_addr如果这个成员时字符串或者字符数组类型那么用strcmp比较

[解决办法]

C/C++ code

#include <stdio.h>#include <winsock2.h>int main(){    char buff[255];    WSAData wsaData;    WSAStartup(MAKEWORD(2, 2), &wsaData);    hostent * hostaddr,*tmp;          gethostname(buff, sizeof(buff));    hostaddr=gethostbyname(buff);        printf("Host name is: %s\n", buff);     printf("ip:%s\n",inet_ntoa(*(struct in_addr *)hostaddr->h_addr));{ // addchar chCurrentIP[256];char *pStr = inet_ntoa(*(struct in_addr *)hostaddr->h_addr);int i = 0;while (pStr[i] != '\0' && i < 256){    chCurrentIP[i] = pStr[i];    i++;}chCurrentIP[i] = '\0';}    while (1)     {    tmp = gethostbyname(buff);        if(strcmp(chCurrentIP, inet_ntoa(*(struct in_addr *)tmp->h_addr)) == 0)            puts("ip 未改变");        else {            printf("ip 改变为:%s\n",inet_ntoa(*(struct in_addr *)tmp->h_addr));{ //add pStr = inet_ntoa(*(struct in_addr *)hostaddr->h_addr);i = 0;while (pStr[i] != '\0' && i < 256){    chCurrentIP[i] = pStr[i];    i++;}chCurrentIP[i] = '\0';}        }        Sleep(3000);    }            WSACleanup();    return 0;}
[解决办法]
inet_ntoa
The Windows Sockets inet_ntoa function converts an (Ipv4) Internet network address into a string in Internet standard dotted format.

char FAR * inet_ntoa (
 struct in_addr in 
);
  
Parameters
in  
[in] A structure that represents an Internet host address.  
Remarks
The inet_ntoa function takes an Internet address structure specified by the in parameter and returns an ASCII string representing the address in ".'' (dot) notation as in "a.b.c.d''. The string returned by inet_ntoa resides in memory that is allocated by Windows Sockets. The application should not make any assumptions about the way in which the memory is allocated. The data is guaranteed to be valid until the next Windows Sockets function call within the same thread, but no longer. Therefore, the data should be copied before another Windows Sockets call is made. 
 
Return Values
If no error occurs, inet_ntoa returns a char pointer to a static buffer containing the text address in standard ".'' notation. Otherwise, it returns NULL.  

QuickInfo
 Windows NT: Yes
 Windows: Yes
 Windows CE: Use version 1.0 and later.
 Header: Declared in winsock2.h.
 Import Library: Link with ws2_32.lib.

See Also
inet_addr

  

[解决办法]
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谢谢 gqjjqg

你写出的代码 完全可行。但只能监视一个 ip 如果本地连接 设为192.168.0.1  我又登陆了拨号上网
就是本机有两个 ip了
这样的情况下 就是
ip1:inet_ntoa(*(struct in_addr *)tmp->h_addr_list[0]);
ip2:inet_ntoa(*(struct in_addr *)tmp->h_addr_list[……
 

 

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