我要评论脚本功能：通过icmp ping或tcp/syn探测指定的域名，探测前检测域名是否有效。
file: check.host.pl
#!/usr/bin/perl
use strict;
use net::ping;
use net::dns;
use time::hires qw();
$| = 1;
my $default_timeout = 2;
my $ping_timeout = 2;
my $dns_timeout = 3;
### 查询域名是否有效
sub querydomain {
my $domain = shift();
my $query = '';
my $dns = net::dns::resolver->new(
tcp_timeout => $dns_timeout, udp_timeout => $dns_timeout, retry => 1
);
my @nameservers = qw/8.8.8.8 114.114.114.114/;
$dns->nameservers(@nameservers);
eval {
$query = $dns->search($domain,'a');
};
if ($@ or ! $query) {
my $err = $dns->errorstring ;
print "err: query $domain failed: $errn";
return if ($err =~ /nxdomain/);
}
return 'ok';
}
### return nothing is failed, other is ok
sub pinghost {
my $arg = shift();
return 1 if (ref $arg ne 'hash');
my $p;
eval { $p = net::ping->new($arg->{'proto'},$default_timeout,0) };
if ($@) {
warn "err to create net::ping object: $@n";
return;
}
$p->hires();
my ($host,$duration,$hip,$rep,$ret);
### tcp/syn ping
if ($arg->{'proto'} eq "syn") {
$p->{port_num} = $arg->{'port'};
$p->ping($arg->{'host'},$ping_timeout);
if (($host,$duration,$hip) = $p->ack()) {
printf("ack reply from $arg->{'host'}[%s] time=%.2f msn", $hip, $duration * 1000);
$ret = 'ok';
} else {
warn "syn request for $arg->{'host'} timed out.n";
}
}
### icmp ping
else {
($rep,$duration,$hip) = $p->ping($arg->{'host'},$ping_timeout);
if ($rep) {
printf("echo reply from $arg->{'host'}[%s] time=%.2f msn", $hip, $duration * 1000);
$ret = 'ok';
}
else {
warn "ping request for $arg->{'host'} timed out.n";
}
}
$p->close;
undef($p);
return $ret;
}
my $arg = { proto => 'syn', port => 80 };
my $host = $argv[0];
my $proto = $argv[1];
die "usage: $0 [icmp]n" if (! $host);
$arg->{'host'} = $host;
$arg->{'proto'} = $proto if ($proto);
my $code;
if (&querydomain($host) eq 'ok' and $code = &pinghost($arg)) {
print "$host is online !n";
}
else {
print "$host is down !n";
}
测试例子：
# ./check.host.pl 2013.jb51.net err: query 2013.jb51.net failed: nxdomain 2013.jb51.net is down ! # ./check.host.pl www.jb51.net ack reply from www.jb51.net[173.255.214.254] time=307.04 ms www.jb51.net is online ! # ./check.host.pl jb51.net icmp echo reply from jb51.net[173.255.214.254] time=205.61 ms jb51.net is online ! # ./check.host.pl chinagfw.com icmp ping request for chinagfw.com timed out. chinagfw.com is down !
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