Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi monks,
when I tried run the script below, I got the following error:
Software error:
Can't use an undefined value as a symbol reference at
/home/www/myspace.superihost.com/cgi-bin/script.pl line 16.
What should be corrected? 
#!/usr/bin/perl
use CGI::Carp qw(fatalsToBrowser);
use strict;
use URI;
use IO::Socket;

my $showOpenedSockets=1;

my $server = IO::Socket::INET->new (
   LocalPort => 8080,
   Type      => SOCK_STREAM,
   Reuse     => 1,
   Listen    => 10);


binmode $server;

while (my $browser = $server->accept()) {
  print "\n\n--------------------------------------------\n";

  binmode $browser;

  my $method              ="";
  my $content_length      = 0;
  my $content             = 0;
  my $accu_content_length = 0;
  my $host;
  my $hostAddr;
  my $httpVer;

  while (my $browser_line = <$browser>) {
    unless ($method) {
      ($method, $hostAddr, $httpVer) = $browser_line =~ /^(\w+) +(\S+)
+ +(\S+)/;

      my $uri = URI->new($hostAddr);

      $host = IO::Socket::INET->new (
        PeerAddr=> $uri->host,
        PeerPort=> $uri->port );

        die "couldn't open $hostAddr" unless $host;

      if ($showOpenedSockets) {
        print "Opened ".$uri->host." , port ".$uri->port."\n";
      }

      binmode $host;

      print $host "$method ".$uri->path_query." $httpVer\n";
      print "$method ".$uri->path_query." $httpVer\n";
      next;
    }

    $content_length = $1 if      $browser_line=~/Content-length: +(\d+
+)/i;
    $accu_content_length+=length $browser_line;

    print $browser_line;

    print $host $browser_line;

    last if $browser_line =~ /^\s*$/ and $method ne 'POST';
    if ($browser_line =~ /^\s*$/ and $method eq "POST") {
      $content = 1;
      last unless $content_length;
      next;
    }
    if ($content) {
      $accu_content_length+=length $browser_line;
      last if $accu_content_length >= $content_length;
    }
  }
  print "\n\n....................................\n";
  
  $content_length      = 0;
  $content             = 0;
  $accu_content_length = 0;
  while (my $host_line = <$host>) {
    print $host_line;
    print $browser $host_line;
    $content_length = $1 if $host_line=~/Content-length: +(\d+)/i;
    if ($host_line =~ m/^\s*$/ and not $content) {
      $content = 1;
      #last unless $content_length;
      next;
    }
    if ($content) {
      if ($content_length) {
        $accu_content_length+=length $host_line;
        #print "\nContent Length: $content_length, accu: $accu_content
+_length\n";
        last if $accu_content_length >= $content_length;
      }
    }
  }
  $browser-> close;
  $host   -> close;
}

[download]

Replies are listed 'Best First'.
Re: Error "undefined value as a symbol reference "
by polettix (Vicar) on Apr 22, 2005 at 10:36 UTC
    I don't have the time to try your code, but if line 16 is the one calling binmode $server; I bet it has to do with the fact that you don't check $server validity after the call to IO::Socket::INET->new.

    As a general rule, always check that things dinamically set up are ok before using them.

    Flavio (perl -e 'print(scalar(reverse("\nti.xittelop\@oivalf")))')

    Don't fool yourself.
[reply]
[d/l]
[select]
Re: Error "undefined value as a symbol reference "
by Anonymous Monk on Apr 22, 2005 at 10:36 UTC
    You aren't checking (and taking appropriate action) whether IO::Socket::INET->new returns a true value. Creation of sockets might fail.
[reply]
      What should be corrected? (it's http-proxy script, I'd used ready code, I am not a very familiar in perl)
[reply]

        When you open your socket, you can do something else if it didn't open. For instance, if you wanted the program to end immediately:

        my $server = IO::Socket::INET->new (
   LocalPort => 8080,
   Type      => SOCK_STREAM,
   Reuse     => 1,
   Listen    => 10)
or die ("Can't open socket : $!");

        [download]

        It's a good idea to check anything that has a potential to fail. (opening files, closing files that you've written to, opening database connections, etc.)

[reply]
[d/l]
Re: Error "undefined value as a symbol reference "
by cog (Parson) on Apr 22, 2005 at 10:40 UTC
    On a side note, ++ for putting the error in blue. Much easier on the eye.
[reply]

      On a side note, ++ for putting the error in blue. Much easier on the eye.

      That is really dependent on which theme the user has chosen.
[reply]
        It's also called sarcasm
[reply]

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