Android without Proxy not working?

I need the condition of setting no proxy in my application; for that I used the following code:

URL url = null;

try {
    url = new URL(uri.toURL().toString());
} catch (MalformedURLException e3) {
    e3.printStackTrace();
}

try {
    //client = (HttpURLConnection) url.openConnection(java.net.Proxy.NO_PROXY);
    Properties systemProperties = System.getProperties();

    systemProperties.setProperty("http.nonProxyHosts",ServerIP);
    systemProperties.setProperty( "proxySet", "false" );
    systemProperties.setProperty("http.proxyHost","");
    systemProperties.setProperty("http.proxyPort","");
    URLConnection conn = url.openConnection(Proxy.NO_PROXY);


    conn.connect();
} catch (IOException e3) {
    e3.printStackTrace();
}

But I got network unreachable exception!!

Any help!!