RE: checking if the macjhine is connected to the network from within tomcat.

[Ralph Einfeldt <ra...@uptime-isc.de>]

If you pull the cable the dns lookup fails.
The problem is, that the java libraries cache failed lookups per default.
In 1.4.1 the cache latency is 10 seconds. I don't know what it is for 
other versions
You have to disable the lookup caching (AFAIK only possible in JDK >= 1.4):

http://java.sun.com/j2se/1.4.1/docs/api/java/net/InetAddress.html

Otherwise you can try to use the IP.

> -----Original Message-----
> From: Manu Kumar [mailto:ManuK@digitalthink.com]
> Sent: Wednesday, May 21, 2003 12:43 AM
> To: 'Tomcat Users List'
> Subject: checking if the macjhine is connected to the network from
> within tomcat.
> 
> 
> Hello All , 
> 
> I have a webapp which needs to determine if the machine its 
> running on is
> connected to the net or not.
> [we have a desktop application which uses tomcat in embedded 
> mode to deliver
> some html content and do various other stuff ].
> 
> currently i am using URL class to create a URL instance to 
> point to say
> www.google.com , try to open the InputStream and if i get 
> some ecxception , 
> return result as not connected.
> 
> the situations which i test are : 
> 
> online --> go offline [yank the cable off :-) ] --> go 
> online. this works
> fine.
> offline --> online --> offline . this always keeps returning 
> as offline.
> 
> if i run the same code outside of tomcat , it works fine in 
> both cases.
> 
> 
> any help would be greatly appreciated .. 
> 
> does anyone have a better way to detect net connectivity 
> [without doing
> native calls] ?
> 
> 
> thanks,
> 
> manu
> 
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