Scalar value errors (with IO :: Socket)

Question

This is my current code:

#!/usr/bin/perl -w use strict; require IO::Socket; while (<>) { chomp(my $host = $_); my @header; print "Connecting to: $host\n"; my $socket = new IO::Socket::INET( PeerAddr => $host, PeerPort => 80, Proto => 'tcp') || print "Could not connect: $!\n"; print "Connected.\n"; print $socket "GET / HTTP/1.0\n\n"; my $i = 0; while (<$socket>) { @header[$i] = $_; $i++; } $i = 0; print "--------------------------------------\n"; while ($i <= 8) { print "@header[$i++]"; } print "-------------------------------------\n"; print "Finished $host\n\n"; } 

If, when I go through the list of IP addresses and the host is denied, instead of continuing with the next IP address, it will give me the error "Cannot use string (" 1 ") as a ref character, whereas" strict refs "in use".

If I then changed @header [$ i] = $; to $ header [$ i] = $; I am also getting the same error. How can I make this script better.

Answer 1

The problem is how you install $socket :

 my $socket = new IO::Socket::INET( PeerAddr => $host, PeerPort => 80, Proto => 'tcp') || print "Could not connect: $!\n"; 

Since you are using the || operator which has a higher precedence than = , this operator is parsed as

 my $socket = (new IO::Socket::INET(...) || print ...); 

If new IO::Socket::INET returns false (as if the connection failed), print will be executed and its return value (usually 1 ) will be assigned to $socket . When you then try to use $socket as

Perl notices that a value of 1 is not really a reference to an object and produces an error message.

If you used the low-priority operator or instead of || , the value of $socket would be undef instead of 1 , and the error message you would get would be something like Can't use an undefined value as a symbol reference ... Of course, this would not solve your problem, but at least it could facilitate the diagnosis.

To fix this problem, you need to fix your code so that you do not continue to execute the rest of the loop body if the connection fails. One way to do this would be as follows:

 my $socket = new IO::Socket::INET( PeerAddr => $host, PeerPort => 80, Proto => 'tcp'); unless ($socket) { print "Could not connect: $!\n"; next; # skip the rest of the loop } 

Answer 2

Wouldn't it be a simple decision to use a version with a lower priority of "or" that has a lower priority than "="?

 my $socket = new IO::Socket::INET( PeerAddr => $host, PeerPort => 80, Proto => 'tcp') or print "Could not connect: $!\n"; 

In fact, the 'or' and 'xor' operators have the lowest operator priority (see perlop).