Re^2: IO::Select - reading multiple lines

[nagalenoj]

in reply to Re: IO::Select - reading multiple lines
in thread IO::Select - reading multiple lines

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;
             }
         }
}

Client side

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

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.

[zentara]

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

[nagalenoj]

sysread returns 0, only when the other end exits. Getting into blocking mode, which is not desired. I expect the program to wait in select not in sysread.

[zentara]

You might be interested in trying ioctl, see IPC3 buffer limit problem. You can google for ioctl on sockets and let your mind get boggled, and yearn for the simplicity of <>. :-)