RE: [PHP] Checking for internet connection.
| From: | Bob McConnell | Date: | Mon, 21 Dec 2009 14:05:10 +0000 |
| Subject: | RE: [PHP] Checking for internet connection. | ||
| References: | 1 2 3 4 5 6 7 | Groups: | php.general |
| Request: | Send a blank email to php-general+get-300624@lists.php.net to get a copy of this message | ||
From: Andy Shellam
>> By attempting to connect you will implicitly query DNS (which itself
>> is a connection to server).
>
> No it's not - it's putting out a packet targeted at an IP address
> and hoping a server will answer - hence why multi-cast works for
> DNS because you're not directly connecting to a specified server,
> like you do with TCP/IP. I believe it's similar for ping which is
> why it's used so commonly in monitoring applications.
>
> > If you're not online you won't be able to
>> resolve the domain name.
>
> Exactly - so if all the OP wanted to check for was a working
> Internet connection, then DNS is a better way to go IMHO.
Both at home and at work there are caching DNS on the LAN. So a DNS
request may come back with a valid IP address when the WAN connection is
down. I still won't be able to connect to the remote site.
Bob McConnell