From Forum Nokia Wiki

The below code demonstrates retrieving of the host address in Symbian C++.

Library needed:

LIBRARY  esock.lib euser.lib insock.lib

Headers

#define MAX_IP_ADDR_LEN  16
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <in_sock.h>

Getting Host address

/*
 * ret buf :- on return contains the  Host Address
 * ret TInt :- Error codes KErrNone if success system wide error codes
 */
 
TInt GetHostAddress(char *buf)
{   
   RSocketServ        iSocketServer;
   RSocket            iSockClient;
   TRequestStatus     iStatus;
   TBuf<(MAX_IP_ADDR_LEN)>      buffer;	
   TBuf8<(MAX_IP_ADDR_LEN*2)>     buf_8bit;          
   char           ip_addr_l[MAX_IP_ADDR_LEN];
   TRequestStatus     protostartStatus;
   TBool            ip_found_l = EFalse;
   TInt               Err;
 
 
   Err = iSocketServer.Connect();
   if (Err != KErrNone)
   {
	  return (Err);
   }
 
   iSocketServer.StartProtocol(KAfInet,KSockStream,KProtocolInetTcp,protostartStatus);
   User::WaitForRequest(protostartStatus);
 
   if (protostartStatus.Int()!=KErrNone)
   {       
       iSocketServer.Close();
       return (protostartStatus.Int());
   }
 
   Err = iSockClient.Open(iSocketServer,KAfInet,KSockStream,KProtocolInetTcp);
   if (Err != KErrNone)
   {
 
      iSocketServer.Close();
      return (Err);
   }
 
   TSoInetInterfaceInfo* inf = new TSoInetInterfaceInfo;
 
   if(inf ==NULL)
   {
 
      iSockClient.Close();
      iSocketServer.Close();
      return KErrNoMemory;
   }
 
   TPckg<TSoInetInterfaceInfo> opt(*inf);
 
   /* Set SocketOption For enumerating interfaces */
   Err = iSockClient.SetOpt(KSoInetEnumInterfaces, KSolInetIfCtrl);
 
   if (Err != KErrNone)
   {
      iSockClient.Close();
      iSocketServer.Close();
      delete inf;
      return Err;
   }
 
   /* Start Enumerating the Interfaces */
   while (iSockClient.GetOpt(KSoInetNextInterface, KSolInetIfCtrl,opt) == KErrNone)
   {
 
      inf->iAddress.Output(buffer);
 
      buf_8bit.Copy(buffer);
      memset(ip_addr_l, 0, MAX_IP_ADDR_LEN);
      strcpy(ip_addr_l, (char *)buf_8bit.PtrZ());
 
      if (inf->iAddress.IsUnspecified())
      { 
         // Display UnSpecified  
      }
      else if (inf->iAddress.IsLoopback())
      {
	 // display LoopBack
      }
	  else if(inf->iAddress.IsLinkLocal())
      {
          // Display LinkLocal address
      }
      else
      {
 
         strcpy(buf, ip_addr_l);         
 
         ip_found_l = ETRUE; 
         break;  
      } 	
   }//end of while
 
   /* Free the resources */
   iSockClient.Close();
   iSocketServer.Close();
   delete inf;
 
   if (ip_found_l == ETRUE)
   {
      return KErrNone;
   }
   else
   {
      return KErrNotFound;
   }
 
 
 
}