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Determining if a computer is online.

Posted on 2003-11-11
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Last Modified: 2010-04-16
I am trying to determine if a computer is online.  I do this before every server call so I can determine if the server is down, or the client is not connected.  This method does not work for two reasons:  1.  It takes forever to timeout if the computer is offline.  2.  the call doesn't work if you do it too many times in a row (for hammering protection) even if you are online.

Is there a native method I can call or something that will work better?

public static bool ComputerOnline()
{
          System.Net.HttpWebRequest wr = (System.Net.HttpWebRequest)System.Net.WebRequest.Create("http://google.com/");
          try            
          {
      System.Net.HttpWebResponse ws = (System.Net.HttpWebResponse)wr.GetResponse();
      return true;
          }
          catch
          {
      return false;
          }
}
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Comment
Question by:jjacksn
2 Comments
 
LVL 6

Expert Comment

by:martinv
ID: 9727161
There could be several ways how to make it faster:

- use IP address instead of DNS. DNS resolving can take some time, and if you are offline DNS server timeout can be long.

- if you want to know that computer is live (and not it's webserver) use PING instead of getting web server response. For ping class see http://www.eggheadcafe.com/articles/20020209.asp  (you may want to remove Dns.GetHostByName calls from the source code)
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LVL 18

Accepted Solution

by:
testn earned 250 total points
ID: 9727179
To check whether the client is online
http://www.csharphelp.com/archives3/archive499.html
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