Re: Is there a clean way to get my default IP address.
Re: Is there a clean way to get my default IP address.
- Subject: Re: Is there a clean way to get my default IP address.
- From: Rustam Muginov <email@hidden>
- Date: Tue, 6 Dec 2005 10:55:11 +0300
Here is a scary but useful technote about this question:
http://developer.apple.com/technotes/tn/tn1145.html
--
Sincerely,
Rustam Muginov
On Dec 6, 2005, at 12:28 AM, John Draper wrote:
Hi,
I'm trying to get my IP address under program control...
I cannot use the "gethostname/gethostbyname" combination
because I could have many devices. Is there a Mac Carbon
call that can give me my IP address in dotted form?
For some reason, my earlier implementation shown
below seems to "break" another call to it later on...
char *
getMyIPAddress(char *myhostname)
{
int result;
struct hostent *myHost;
struct in_addr dstAddr;
char *ip;
result = gethostname(myhostname, 100);
if (result == -1)
return NULL;
myHost = malloc(sizeof (struct hostent));
myHost = gethostbyname(myhostname); <---- this works as
expected
memcpy((char *) &dstAddr, myHost->h_addr_list[0], myHost->h_length);
ip = inet_ntoa(dstAddr);
free(myHost);
return(ip);
}
This routine works fine, but it "breaks" the program that calls this
code.... It returns my hostname in "myhostname" which is a char *
to a hostname.
The IP address it returns is a char * returned from inet_ntoa(dstAddr)
which I presume to be an allocated pointer, returning my IP address.
At least it works this way.... BUT!!!!!
later on, when I call this block of code...
struct hostent* he;
if ((he = gethostbyname(buffer)) != NULL) { <---- NOTE HERE
if (strchr(he->h_name, '.') != NULL) {
strncpy(buffer, he->h_name, sizeof(buffer));
}
else {
WarningLog( << "local hostname does not contain a domain part");
}
}
As indicated above, as soon as I call "gethostbyname" I get the
following...
*** malloc[3311]: Deallocation of a pointer not malloced: 0xa01c05f4;
This could be a double free(), or free() called with the middle of an
allocated block; Try setting environment variable MallocHelp to see
tools to help debug
*** malloc[3311]: Deallocation of a pointer not malloced: 0x7c030378;
This could be a double free(), or free() called with the middle of an
allocated block; Try setting environment variable MallocHelp to see
tools to help debug
*** malloc[3311]: Deallocation of a pointer not malloced: 0x48277375;
This could be a double free(), or free() called with the middle of an
allocated block; Try setting environment variable MallocHelp to see
tools to help debug
*** malloc[3311]: Deallocation of a pointer not malloced: 0x7c601b78;
This could be a double free(), or free() called
Then, in the first routine I comment out the line...
myHost = gethostbyname(myhostname);
And by doing that, it works just fine when I call the 2nd one.
Can someone please shed some light on this very confusing issue?
John
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