Has anyone experience of using the serial ports under Windows? I'm trying to send commands to the modem and read the response. I thought that I'd read all the relevant bits in the open tutorial and I have the following code
use warnings;
use Fcntl;

my $tty = "COM3";
my $text = shift || "ATH0";

sysopen(COM,$tty,O_RDWR) || die "Can't open $tty $^E";

transmit("$text");
receive();

sub transmit {
    my $data = shift;
    $data .= "\r";
    @ascii = unpack("C*",$data);
    print "transmit: [@ascii]\n";
    syswrite(COM,$data);
}

sub receive {
    sysread(COM,$buf,4);
    @ascii = unpack("C*",$buf);
    print "receive: [@ascii]\n";
    return $buf;
}

[download]
However when I run the script it hangs on the sysread instead of returning O.K. as expected. I think the port is opening correctly, because when something else is using the port the open fails with an "Access denied" message.

In reply to Accessing serial ports under Windows by Odud

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