Question

Lookup IP address from hostname (C/socket)

Asked by: pluim

How do I find the IP address for a given host, in C?
This is on a UNIX box (AIX), TCP/IP installed and
DNS available. Assume a hostname has no aliases and
only one associated IP address.

This is the code I have so far:

  struct hostent      *host;
  struct sockaddr_in  sa;
  char                ipaddress[32];

  host=gethostbyname("someserver.com");

  ... get IP address ...

  memset (&sa, '\0', sizeof(sa));
  sa.sin_family      = AF_INET;
  sa.sin_addr.s_addr=inet_addr(ipaddress);
  sa.sin_port        = 80;          

Thanks,
pluim.

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Asked On
1999-07-15 at 18:34:03ID10183323
Tags

ip

,

address

,

c

,

hostname

Topic

Unix Networking

Participating Experts
2
Points
100
Comments
3

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Answers

 

by: msmanjuPosted on 1999-07-15 at 21:31:08ID: 1583896

try this

sa.sin_addr.s_addr= *((unsigned long *)host->h_addr);

 

by: pluimPosted on 1999-07-16 at 06:39:04ID: 1583897

msmanju, thanks for the answer. However, as I hoped the code would explain, I want the IP address in a readable format (hence the char ipaddress[32]).
Something in the form "1.2.3.4".

Thanks.

 

by: alextrPosted on 1999-07-19 at 02:44:33ID: 1583898

struct hostent *hp;
 struct in_addr in;

hp = gethostbyname(argv[1]);

 (void) memcpy(&in.s_addr, *(hp->h_addr_list), sizeof (in.s_addr));
 (void) printf("%s\n", inet_ntoa(in));

20120131-EE-VQP-002

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