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Full Discussion: How to get IP Address of machine?
Top Forums Programming How to get IP Address of machine? Post 42248 by DreamWarrior on Friday 24th of October 2003 11:16:36 AM
Old 10-24-2003
I didn't think that inet_ntoa would work because I didn't have an in_addr structure to pass it, I only had a struct sockaddr_in, and I didn't see an in_addr structure residing within that. So I didn't want to sit and guess what part (if any) of that structure to pass it, or try and find something to extract that information. However the man page for what I ended up using (inet_ntop) does say that is equivalent to inet_ntoa, although it takes entirely different arguments.

Anyway, I found code (in the Steven's book) to obtain my desired results. I knew we had a copy laying around here somewhere, I just couldn't find it...but you're right it is the God of network books.

So (drumroll) for those curious, this is what I ended up doing. Keep in mind that I needed to go from an integer socket descriptor to an IP, so this code may not be exactly what you need.

Just a quick note, the saddr and slen variables work fine with the type I gave them for HP-UX (and Redhat - while it gives compile warnings it works)). However, some OSes want saddr to be of type struct sockaddr *, and some want slen to be of type socklen_t. And while that may work, sockaddr doesn't have the internet sin_addr field required...so some typecasting may need to be done to shut those compilers up.

Also, this isn't the exact code I used, but it does the job and presents the basics without all the garbage I put around it for my particular needs.

Code:
int getIP(int sfd, char *buf, size_t bufSize, int getMine)
{
   int  rVal;
   struct sockaddr_in saddr;
   int slen;

   /* get saddr depending on what caller wants */

   if (getMine)
   {
      rVal = getsockname(sfd, &saddr, &slen);
   }
   else
   {
      rVal = getpeername(sfd, &saddr, &slen);
   }

   /* insure saddr was filled in */

   if (rVal < 0)
   {
      /* it wasn't */

      rVal = 0;
   }
   else
   {
      /* it was - convert address in sin_addr to dotted IP */

      rVal = (inet_ntop (AF_INET, &saddr.sin_addr, buf, bufSize) == NULL) ? 0 : 1;
   }

   return rVal;
}

Also, if you wanted to know port information, you could get it with:

port = ntohs(saddr.sin_port);

Provided, of course, that saddr was filled in.

getMine allows you to get information regarding the local socket connection, otherwise (by passing it 0) you get information regarding the connection at the other end (the peer).

And that's it...hope this helps those curious.
 

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LEARN ABOUT SUNOS

in

in.h(3HEAD)							      Headers							       in.h(3HEAD)

NAME

       in.h, in - Internet Protocol family

SYNOPSIS

       #include <netinet/in.h>

DESCRIPTION

       The <netinet/in.h> header defines the following types through typedef:

       in_port_t       An unsigned integral type of exactly 16 bits.

       in_addr_t       An  unsigned  integral  type  of exactly 32 bits. The <netinet/in.h> header defines the in_addr structure that includes the
		       following member:

       The <netinet/in.h> header defines the in_addr structure that includes the following member:

       in_addr_t       s_addr

       The <netinet/in.h> header defines the type sa_family_t as described in socket.h(3HEAD).

       The <netinet/in.h> header defines the following macros for use as values of the level argument of getsockopt() and setsockopt():

       IPPROTO_IP	       Dummy for  IP

       IPPROTO_ICMP	       Control message protocol

       IPPROTO_TCP	       TCP

       IPPROTO_UDP	       User datagram protocol The <netinet/in.h> header defines the following macros for use as destination addresses  for
			       connect(), sendmsg(), and sendto():

       INADDR_ANY	       Local host address

       INADDR_BROADCAST        Broadcast address

       The  <netinet/in.h>  header  defines the sockaddr_in structure that is used to store addresses for the Internet protocol family.  Values of
       this type must be cast to struct sockaddr for use with the socket interfaces.

   Default
       For applications that do not require standard-conforming behavior (those that use the socket interfaces described in section(3SOCKET)	of
       the reference manual; see Intro(3) and standards(5)), the <netinet/in.h> header defines the sockaddr_in structure that includes the follow-
       ing members:

       sa_family_t     sin_family
       in_port_t       sin_port
       struct in_addr  sin_addr
       char	       sin_zero[8]

   Standard conforming
       For applications that require standard-conforming behavior (those that use the socket interfaces described in section(3XNET) of the refer-
       ence  manual;  see Intro(3) and standards(5)), the <netinet/in.h> header defines the sockaddr_in structure that includes the following mem-
       bers:

       sa_family_t     sin_family
       in_port_t       sin_port
       struct in_addr  sin_addr
       unsigned char   sin_zero[8]

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       Intro(3), connect(3SOCKET), connect(3XNET),  getsockopt(3SOCKET),  getsockopt(3XNET),  sendmsg(3SOCKET),  sendmsg(3XNET),  sendto(3SOCKET),
       sendto(3XNET), setsockopt(3SOCKET), setsockopt(3XNET), socket.h(3HEAD), attributes(5), standards(5)

SunOS 5.10							    30 Aug 2002 						       in.h(3HEAD)
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