使用pack函数发送二进制数据

sub send_msg {
    my ($msg_len, $device, $msg) = @_;
    my $sock = IO::Socket::INET->new(PeerAddr => $remote_host,
                                   PeerPort => $remote_port,
                                   Proto => "tcp",
                                   Type => SOCK_STREAM) or die "can't connect to $remote_host\n";

    $msg = pack("A$msg_len", $msg);
    $msg = "" if ($device < 0);
    $msg_len = 0 if ($device < 0);
    $msg_len = pack("i1", $msg_len);
    $device = pack("i1", $device);
    print $sock $msg_len;
    print $sock $device;
    print $sock $msg;
    close($sock);
}