use constant MAXLEN => 1500;
.....
my $mesg';
my $buff;
while(my $read = $self->{csocket}->recv($buff, MAXLEN)) {
    $mesg.= $buff;
    last if( $read < MAXLEN );
}

use constant MAXLEN => 1500;
......
my $mesg';
my $buff;
my $conn = $self->{csocket};
while( my $read = read( $conn, $buff, MAXLEN ) ) {
    $mesg.= $buff;
    last if( $read < MAXLEN );
}