# as a start change 
 my $line = <$fh>;
 #to 
 sysread $fh, my $line, 1024;,
[download]

That is indeed the correct solution (to use sysread). However, it's worse than simply because there's no newline.

select generally doesn't work properly if you mix in buffered reads and writes; select will perpetually think something is readable, or nothing is readable, because the buffering has over-read or under-read on the handle.

This means that whenever you're using select, either directly or indirectly through IO::Select or some event loop, then you must use sysread and syswrite (not print, <$fh>, read(), etc.).

You often end up doing your own buffering with sysread and syswrite, because often you're still dealing with line-oriented protocols. This is fairly boilerplate stuff, and it's recommended to use an event loop that does most of it for you (e.g. POE, Event, IO::Async, etc.).

Monks,

I've many questions raising now., Let me tell what's in my mind.

So, is it a very worse idea to use <$fh> to read from a socket? Because, it is failing straight away without doing lot of magic(stuffs) in the code.

Server side

while(@ready = $sel->can_read) {
        if($fh == $lsn) {
            # Accept the socket
            $new = $lsn->accept;
            $sel->add($new);
            print "New client accepted\n";

            print $new "abc\n";
            print $new "abcd\n";
            print $new "abcde\n";
            print $new "abcdef\n";
        }
         else {
            # Process socket
            $a = <$fh> ;
             if (not defined $a)  {
                $sel->remove($fh);
                $fh->close;
                print "Client closed\n";
             }
             else  {
                print $a;
             }
         }
}
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Client side

while(@ready = $sel->can_read) {
    foreach $fh (@ready) {
        my $rr = <$fh>;
        
        exit if ( not defined $rr );
        print $rr;
    }
}
[download]

In the above sample, client is receiving only abc(first message) sent by server. When server quits, can_read is returning and client is receiving the remaining messages, not blocking. Getting messages one after another.

Then, I tried with sysread as suggested here. When using sysread, should I read byte by byte till '\n'? Because, I don't know the size of the message. Is it a good way to read byte by byte, do concatenation and then process the message?(I don't think so.)

Please, explain me some way to write a error free way(pleasant way too) to receive messages in socket.. or let me know what am I doing wrong.

Thanks.

is it a very worse idea to use <$fh> to read from a socket

Yeah, you are best off using sysread, and there are a few ways to use sysread, depending on your situation, you can put it in various staement forms

 while( sysread $fh, $str, 8192, length $str ) {
#or
 do { $rc = sysread(FH, $buff, 5000000, length($buff)) ; } while ($rc
#or
if ( sysread( $cli, $buffer, 1024 ) ) {}
# etc etc
[download]

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I'm not really a human, but I play one on earth.
Old Perl Programmer Haiku ................... flash japh