UDP Server doesn't receive before newline

[nitin1704]

So I made a simple UDP client and server using IO::Socket. The code is given below. The problem is that the server prints the message from client only when it ends with a newline. Is there a way to change this? I tried disabling output buffering on the client side, but that didn't work.

client.pl

use IO::Socket;
use strict;
use warnings;

my $sock = IO::Socket::INET->new(
    Proto    => 'udp',
    PeerPort => 23456,
    PeerAddr => '10.254.83.40',
) or die "Could not create socket: $!\n";
select($sock); $|=1;
$sock->send("message from client") or die "Send error: $!\n";

server.pl

use IO::Socket;
use strict;
use warnings;

my $server = IO::Socket::INET->new(LocalPort => 23456,
                                Proto     => 'udp')
                        or die "Couldn't be a udp server on port 23456
+: $@\n";
my $MAX_TO_READ = 1024;
my $datagram = '';
while($server->recv($datagram, $MAX_TO_READ)){
        print $datagram;
}

[choroba]

You might find the answer in this thread: Does IO::Select work? Anywhere?.

[zwon]

UDP doesn't have buffering. Buffering happens on the server side -- stdio library buffers output. Try:

print "$datagram\n";

[nitin1704]

That worked. Thanks! Why doesn't the stdio library buffer output like this when I do a normal print statement (instead of doing it like this in a socket-recv() scenario)?

[zwon]

Socket is irrelevant. Try:

perl -e'while(1) { print "Datagram"; sleep 1; }'

check man stdio for your system. Mine (GNU/Linux) says:

Output streams that refer to terminal devices are always line buffered by default; pending output to such streams is written automatically whenever an input stream that refers to a terminal device is read. In cases where a large amount of computation is done after printing part of a line on an output terminal, it is necessary to fflush(3) the standard output before going off and computing so that the output will appear.