I'm working on a project that works with a line by line protocols (POP3 and SMTP). I'm running into a problem where IO::Select->can_read is reporting that a socket doesn't have anything on it when it does. This only happens when I'm reading a bunch of lines from the socket (retrieving a message). Here's a boiled down test example that should connect, get a specified message, and then quit. I should probably be keeping track of states to know what to send next, but this is just to figure out the can_read problem. It hangs on the same line all the time, but will print everything out if more data comes in on the socket. 
#!/usr/bin/perl

use IO::Socket;
use IO::Select;

$user = shift || die "Usage: $0 user password server msgnum\n";
$pass = shift || die "Usage: $0 user password server msgnum\n";
$server = shift || die "Usage: $0 user password server msgnum\n";
$msgnum = shift || die "Usage: $0 user password server msgnum\n";

sub setgreen {
   print "\033[00;32m";
}

sub setred {
   print "\033[00;31m";
}

sub setnormal {
   printf "\033[00m";
}

$dstsock = IO::Socket::INET->new(
        PeerAddr => $server,
        PeerPort => 110,
        Proto => 'tcp');

$readables = IO::Select->new();
$readables->add($dstsock);
$notdone = 1;

while ($notdone) {
    my @ready = $readables->can_read(0);
    foreach $sock (@ready) {
          $data = <$dstsock>;
          if ($data) {
             setred;
             print "$data";             setnormal;
             if ($data =~ /^\+OK Qpopper/) {
                print $dstsock "user $user\r\n";
                setgreen();
                print "user $pass\r\n";
                setnormal;
             }
             if ($data =~ /^\+OK Password/) {
                print $dstsock "pass $pass\r\n";
                setgreen(); 
                print "pass $pass\r\n";
                setnormal;
             }
             if ($data =~ /^\+OK $user/) {
                print $dstsock "retr $msgnum\r\n";
                setgreen();
                print "retr $msgnum\r\n";
                setnormal;
             }
             if ($data =~ /^\.$/) {
                print $dstsock "quit\r\n";  
                setgreen();
                print "quit\r\n";
                setnormal;
             }
              
          } else {
             $notdone = 0;
             close $dstsock;
             close $srcsock;
          }
    }
}

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In reply to IO::Socket should be readable, but isn't.... by blogan

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