How do I create a variable length byte array for socket transmission?

rambo2_981 has asked for the wisdom of the Perl Monks concerning the following question:

I’m new to Perl and am trying to set a variable length byte array that is passed to a socket as a string for output. I have the following which works, but the commented out code doesn’t. What am I doing wrong? Thanks.

use IO::Socket;
use Time::HiRes qw(usleep ualarm gettimeofday tv_interval);
my $sock = new IO::Socket::INET( PeerAddr => '10.10.2.141', PeerPort =
+> '50000', Proto => 'udp' );
die "no socket\n" unless $sock;

$totalNumPkts = 1;
$pktSize = 512;
$dataVal = 'U';
$iPkt = “1“;

for ( $i = 1; $i < $pktSize; $i++ )
{
    $iPkt += "1";
}
$startTime = Time::HiRes::time;

for ( $i = 1; $i <= $totalNumPkts; $i++ )
{
    print "sending msg ..";

    $sock->print( "Hello\n" );
    #$sock->print( $iPkt );
}
$endTime = Time::HiRes::time;
$totalTime = $endTime - $startTime;
printf( " st %f end %f total time=%f time/pkt=%f\n", $startTime, $endT
+ime, $totalTime, $totalTime / 
$totalNumPkts );
printf("done\n");
close( $sock );
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Comment on How do I create a variable length byte array for socket transmission? Download Code

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Re: How do I create a variable length byte array for socket transmission? by dave_the_m (Monsignor) on Jan 10, 2006 at 14:19 UTC
`$iPkt = “1“; for ( $i = 1; $i < $pktSize; $i++ ) { $iPkt += "1"; }` [download] You're using numerical addition rather than string concatenation. try the following instead: `$iPkt .= "1";` [download] or even better, replace the whole loop with `$iPkt = “1“ x $pktSize;` [download] Finally, if you want to send data more complex than just a stream of ASCII "1"s, especially binary data, then you may want to check out the pack() function. Dave.	[reply] [d/l] [select]

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Re: How do I create a variable length byte array for socket transmission?
by dave_the_m (Monsignor) on Jan 10, 2006 at 14:19 UTC

$iPkt = “1“; for ( $i = 1; $i < $pktSize; $i++ ) { $iPkt += "1"; }
[download]

    $iPkt .= "1";
[download]

$iPkt = “1“ x $pktSize;
[download]

Dave.

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