im having difficulty getting my ip from within a winsock program. this is mainly due to my inability to understand this:

    type
       hostent = record
          { official name of host  }
          h_name: pchar;
          { alias list  }
          h_aliases: ^pchar;
          { host address type  }
          h_addrtype: SmallInt;
          { length of address  }
          h_length: SmallInt;
          { list of addresses  }
          case byte of
             0: (h_addr_list: ^pchar);
             1: (h_addr: ^pchar)
       end;

how do i understand the case statement? what does 'case byte of' refer to? in all the c examples i have read, they indicate that h_addr_list should contain an array of addresses for the host, i.e. me. however, the length of this list is always 4 bytes, which is only one address, and it's always the same as h_addr, both pointing to the loopback address. the c examples all use h_addr_list as an array. why isn't this an array here? im seriously confused.

can anybody help me out? i need to know my modem's ip address so that i can instruct other people to connect to that address. its kind of a pain to always have to run ipconfig. my users won't like that, and i shouldn't have to teach them to do that if i can just divine the address within my program.

regards,
ron wilson

It is not an array here because it is not a real array; It's just a pointer to a null-terminated list of names.

The h_addr_list and h_addr pointers can be used interchangably. Probably a name change occurred, and for compatibility reasons both names have been retained.

Michael.

ok - thats what i thought - so they both point to the same memory area. my question is this then: how do i access the list. i guess my pascal syntax is too far gone. i understand pointers pretty well, but in this case, i'm lost. what we have here is a pointer to pchar - ^pchar. so to access the first pchar in the list i would code this:

program test;
var
  pc: pchar;
  h: hostent;
begin
  /* fill h here */
  pc:=stralloc(sizeof(h.h_addr_list^));
  strpcopy(pc,h.h_addr_list^);
  writeln(pc);
end.

how do i access the second pchar? the third? from high school (been a while) i seem to recall adding 1 to the pointer? h.h_addr_list^+1? or maybe inc(h.h_addr_list^)? in my program, the first pchar in the list for the host is almost always 127.0.0.1 - which is a no-brainer. what i need is the second or third address in the list, i.e. my modem ip.

the reverend
(: the goodguys :)
icq 83250263
http://thereverend.coastgames.com/tradewars/

No, no. You can use the fact that a pointer can be considered as a pointer to an array.

I:=0;
While h.h_addr_list[i]Nil do
  begin
  PC:=h_addr_list[i];  // Get pchar pointer
  S:=StrPas(pc);       // Convert to pascal string.
  // Do something with S.
  inc(i)
  end;

Have a look at the inet unit, the GetAlias method. It does exactly the same for Linux.

Michael.

thanks - i tried this once before and i got this compiler error:

_revproxy.pp(37,29) Error: Array type required
_revproxy.pp(344) Fatal: There were 1 errors compiling module, stopping

here is my code. (its under construction, but this at least should compile.

21 function getlocalip: ansistring;
22 var
23   pc: pchar;
24   ac: array[0..255] of char;
25   phe: phostent;
26   i: integer;
27 //  addr: in_addr;
28   s: ansistring;
29 begin
30   if (gethostname(ac,sizeof(ac))=SOCKET_ERROR) then halt;
31   writeln('host name is: ',ac);
32   phe:=gethostbyname(ac);
33   if phe=nil then halt;
34 //  writeln(sizeof(phe^.h_addr_list^));
35
36   i:=0;
37   while not(phe^.h_addr_list[i]=nil) do
38   begin
39     pc:=phe^.h_addr_list[i];
40     s:=strpas(pc);
41     writeln('address ',i,': ',s);
42     inc(i);
43   end;
44   getlocalip:=s;
45 end;

i just assumed i was doing something wrong with my syntax when i got that error. any suggestions?

ron wilson

i think i found the problem... i had delphi compatibility on for the compiler - turned it off and now it compiles... now i'll see if it gives useful information.

the reverend
(: the goodguys :)
icq 83250263
http://thereverend.coastgames.com/tradewars/