Programming

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.