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POPinging computer by name in Java
 

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    <p>I am in the process of writing a simple program that extracts computer names from MySQL Database then stores those names into a String array list (this part works fine). After that I wrote a class and a method that takes a String as a parameter (which will be the computer name) and tries to ping it. Here is the code for that class:</p> <pre><code>public class Ping { public void pingHost(String hostName) { try { InetAddress inet = InetAddress.getByName(hostName); boolean status = inet.isReachable(5000); if (status) { System.out.println(inet.getHostName() + " Host Reached\t" + inet.getHostAddress()); } else { System.out.println(inet.getHostName() + " Host Unreachable"); } } catch (UnknownHostException e) { System.err.println(e.getMessage() + " Can't Reach Host"); } catch (IOException e) { System.err.println(e.getMessage() + " Error in reaching the Host"); } } </code></pre> <p>The problem is that I keep getting <code>UnknownHostException</code> thrown for most computers even if I can ping them manually or if I hard code the computer name as the "hostName". </p> <p>Here is what my main looks like:</p> <pre><code>public static void main(String[] args) throws InstantiationException, IllegalAccessException, ClassNotFoundException, SQLException { ArrayList &lt;String&gt; list = new ArrayList&lt;String&gt;(); MySQLConnect myConnection = new MySQLConnect(); myConnection.importData(list); Ping pingComputer = new Ping(); pingComputer.pingHost(list.get(87)); } </code></pre> <p>Right now I'm just trying to experiment with one computer which is throwing <code>UnknownHostException</code> but can be pinged manually. Anyone have any idea why this is happening?</p> <p>EDIT...</p> <p>Just to explain this a little bit more. For example in main, if I pass these parameters to <code>pingHost</code>:</p> <pre><code>pingComputer.pingHost("ROOM-1234"); </code></pre> <p>It pings fine and returns correct host name/address. But <code>list.get(87)</code> returns same host name "ROOM-1234" but throws <code>UnknownHostException</code>? This has got me really confused and not sure why its not working.</p> <p>EDIT</p> <p>Wow finally figured it out. Reason ping was working when I was passing the string directly like so "ROOM-1234", was because there were no white spaces and getting is from array like so <code>list.get(87)</code> returned same thing but when I checked <code>charLength</code>, it returned a different value :) So I just ended up using <code>trim</code> to get rid of white spaces and now itworks great.</p> <pre><code>pingComputer.pingHost(list.get(87).trim()); </code></pre> <p>Thanks for all the suggestions!</p>
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    1. USgiampaolo
    1. USNick
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    1. COHow is the hostname passed? Is it fully-qualified-domain-name or just the name without domain information?
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      1. USVikdor
    2. COIf you could just show how exactly do you use this method: pingHost. What do you pass there?
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      1. POPinging computer by name in Java
      1. USOndrej Kvasnovsky
    3. COPlease add some examples of actual hostnames that you pass to `pingHost()`.
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      1. USJim Garrison
 

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