get ip address of the machine that my programming is running

djgerbavore · 04-14-2006, 12:17 PM

hi,
I was wondering how to I get the IP address of the local machine that my application is running. I've tried numerous things with no success.

Code:

        struct sockaddr_in server, from;

        int sock;

        sock = socket(AF_INET, SOCK_DGRAM, 0);

        bzero(&server, sizeof(server));

        server.sin_family = AF_INET;
        server.sin_addr.s_addr = INADDR_ANY;
        server.sin_port = htons(6969);

        printf("IP:%s\n", inet_ntoa(server.sin_addr));

All this does is print 0.0.0.0 I read online that INADDR_ANY points to IP address of the machine is their a way to use this variable directly?

thanks,

djgerbavor3

paulsm4 · 04-14-2006, 12:29 PM

Hi -

The easiest way is to call gethostbyname () on your own hostname:
http://shoe.bocks.com/net/

Another way is to call getsockname () on any active connection:
http://faq.cprogramming.com/cgi-bin/...&id=1045780608

You can find your hostname with "gethostname()" (man 2, Linux) or "GetComputerName ()" (Windows)

'Hope that helps .. PSM

graemef · 04-14-2006, 12:33 PM

The INADDR_ANY constant is not the IP address of your machine but a "generic every" IP address and is typically used when creating a listening socket so say I'm listening on any IP address, hence the value of 0.0.0.0

As Paul said use the getHostByName()

graeme

djgerbavore · 04-14-2006, 08:57 PM

Hey guys thanks for the help, but unfortunately, that didn't solve my problem. First gethostbyname, requires me to have a nameserver running or something to translate hostname to ip. which i have none, i have a computer name, but when i use that name i just get 127.0.0.1 which is no good. Secondly, getsockname() doesnt' work, because I'm using UDP, and it requires the socket to be in 'connected' mode which UDP isn't. yet is their still another way I can do this?

thanks,

djgerbavor3

paulsm4 · 04-14-2006, 09:52 PM

To the best of my knowledge, "gethostbyname()" works under all circumstances - via your local /etc/hosts (if that's all you have), or DNS (if available).

I also believe you can configure the behavior with /etc/nsswitch.conf.

Did you try writing a standalone program that did gethostname(), followed by "gethostbyname ()"? What happened?

Plan C might be to do a "popen()" and parse the output from ifconfig, or look in /proc.

PS:
There's also a thread on this very LQ page that might help with your quest, too:
http://www.linuxquestions.org/questi...d.php?t=434241

jlliagre · 04-15-2006, 01:05 AM

See that one too:
http://www.linuxquestions.org/questi...d.php?t=425637