Ok. Thank you that worked however I'd like to ask some questions. I tried to find the answer by looking at the source code however I'm confused by this code
abcd:=PABCD(phe^.h_addr_list[0])^;
I beleive this automaticly parses h_addr_list[0] into the record. Not sure why but that's ok. However when I looked at the winsock source most specifly hostent record type I was not able to winnow any meaning out of.
case byte of 0: (h_addr_list: ^pchar); 1: (h_addr: ^pchar)
Which is the last part of the record. Now please correct me if I'm wrong. but the h_addr_list is an array of bytes, however the type that's declared is a pointer to pchar right? It's just muddy for me. This is my first real forray into compiled languages, I can do what I want to with python or perl but this is a little beyond me.
Thanks Chad
I perfectly understand your confusion -- hostent record type isn't a good example of "nice and clean type design". It was designed in C so it's rather "follow-the-pointers type design".
First of all, forget about "PChar". As you said, h_addr_list[0]^ is not a null-terminated array of chars. It's just array of bytes. You have to look at h_length to now how long (in bytes) it is.
h_addr_list is a "null-terminated list of pointers to addresses". This means that if you want to enumerate all addresses from hostent you have to do something like that
i:=0;
whle phe^.h_addr_list[i] <> nil do
begin
... here is the code to do something with an i-th address.
phe^.h_addr_list[i] is a *pointer* to this address.
phe^.h_length tells you how long is this address, in bytes.Inc(i); end;
That's why I wrote in code attached to last mail that h_length should be 4 for normal Internet address (as long as you forget about IPv6). This means that phe^.h_addr_list[0] is a pointer to four-byte array that contains the address you want to get.
So now we want to extract those four bytes. There are many ways to do this in Pascal. I wrote
abcd:=PABCD(phe^.h_addr_list[0])^;
This line was not doing any "automatic string parsing" -- it was rather telling the compiler "treat phe^.h_addr_list[0] as a pointer to a record TABCD". And record TABCD is just a four-byte array.
One may also write something like that, maybe this will be more clear:
type
TFourByteArray = array[0..3]of byte;
PFourByteArray = ^TFourByteArray;
....
Writeln(Format('%d.%d.%d.%d', [
PFourByteArray(phe^.h_addr_list[0])^[0],
PFourByteArray(phe^.h_addr_list[0])^[1],
PFourByteArray(phe^.h_addr_list[0])^[2],
PFourByteArray(phe^.h_addr_list[0])^[3]
]));Hope this helps, Michalis
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