18. Internet Services

#load "unix.cma";;

let () =
  try
    let addresses = Unix.gethostbyname name in
    let addresses =
      Array.map Unix.string_of_inet_addr addresses.Unix.h_addr_list in
    (* addresses is an array of IP addresses *)
    Array.iter print_endline addresses
  with Not_found ->
    Printf.printf "Can't resolve %s\n" name

(*-----------------------------*)

let () =
  try
    let host = Unix.gethostbyaddr (Unix.inet_addr_of_string address) in
    let name = host.Unix.h_name in
    (* name is the hostname ("www.perl.com") *)
    print_endline name
  with Not_found ->
    Printf.printf "Can't resolve %s\n" address

(*-----------------------------*)

let () =
  try
    let host = Unix.gethostbyaddr (Unix.inet_addr_of_string address) in
    let name = host.Unix.h_name in
    try
      let addresses = Unix.gethostbyname name in
      let addresses =
        Array.map Unix.string_of_inet_addr addresses.Unix.h_addr_list in
      Array.iter print_endline addresses;
      let found = List.mem address (Array.to_list addresses) in
      print_endline (if found then "found" else "not found")
    with Not_found ->
      Printf.printf "Can't look up %s\n" name
  with Not_found ->
    Printf.printf "Can't look up %s\n" address

(* @@INCOMPLETE@@ *)