C / C++ / MFC

<br />
// Config or INI file<br />
# AccessList: Define the access permitted list of IP's <br />
# (use komma as seperator).<br />
AccessList = *.*.*.*<br />
<br />
# DenyLis: Define the noaccess list, any IP matching a member of this<br />
# list will be denied access. The denylist is searched after the<br />
# accesslist (look above).<br />
DenyList = <br />

// Server code (after accepting an incoming client)
{
  ...
  # Check to see if caller can access the server, if not kick him
  if(!&CheckAccess($ENV{REMOTE_ADDR},@AccessList)) {
     &ErrorMessage(*NS,$inp,403,"Access Denied"); exit 0
  }

  # Check to see if the caller is explicitly denied access to the server
  if(&CheckAccess($ENV{REMOTE_ADDR},@DenyList)) {
     &ErrorMessage(*NS,$inp,403,"Access Denied"); exit 0
  }
  ...
}

# Test client IP against access lists, returns true if match
sub CheckAccess {
  my ($who,@list) = @_;
  my $pattern;
  foreach $pattern (@list) {
   $pattern =~ s/\./\\./g ;  #replace . by \.
   $pattern =~ s/\*/\\d\+/g; #replace * by \d+ 
   return 1 if $who =~ /$pattern/;
  }
  return 0;	#search failed
}