i don't know any util but i did myself a simple code for that with perl:
#!/usr/bin/perl
use Net::Ping;
use POSIX qw/strftime/;
if (-e '/var/run/net_test.pid') {
print "net_test already running.\n";
exit;
} else {
system "touch /var/run/net_test.pid";
}
my $host = "www.google.com";
my $ping = Net::Ping->new('icmp');
my $result = $ping->ping($host,2);
if ($result != 1) {
$format = strftime('[%d/%m/%Y %H:%M:%S]',localtime)." Internet is not available...";
$run = `echo $format >> /var/log/virtua_net`;
while ($result != 1) {
$result = $ping->ping($host,2);
sleep 60;
}
$format = strftime('[%d/%m/%Y %H:%M:%S]',localtime)." Internet is back...";
$run = `echo $format >> /var/log/virtua_net`;
} else {
$format = strftime('[%d/%m/%Y %H:%M:%S]',localtime)." Internet is ok...";
$run = `echo $format >> /var/log/virtua_net`;
}
$ping->close();
system "rm -rf /var/run/net_test.pid" if (-e "/var/run/net_test.pid");
exit;
What it does is that it will try to ping google every time it runs and it will then print to a file if it got a reply or not along with the time so you can check later from what time to what time the internet was unavailable.
If you like it i can make the smalls changes to be used in windows and you did need to install ActivePerl that is all.
The only changes needed are paths and commands that may be different on windows nothing else.