Android上的InetAddress.getByName

Question

I do a:

java.net.InetAddress serverAddr;
try {
    serverAddr = java.net.InetAddress.getByName(Server.SERVERNAME);
}
catch (java.net.UnknownHostException exception) {
    //System.err.println ("wrong server name !!!");
    HelloWorldActivity.tv.setText("wrong server name !!!");
    return;
}

in my android application, but it's never resoling the hostname, it always throws an exception, no matter what name I use.

But using the internet on the same emulator works, and I've added

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

to AndoidManifest.xml

and here's the server class for those who assume I have none

public class Server
{
    public static String SERVERNAME = "monster.idsoftware.com";
    public static String SERVERIP = "209.85.129.99";
    public static int SERVERPORT = 27950;
    public static int PROTOCOL = 68;
}

Answer 1

I was having the similar issue and I found out that in some versions of android (from honeycombs) it's not allowed by default to perform network operation from main thread. So you can resolve it in 2 ways. Perform operation in different thread or allow to make network operation in main thread. To do that use something like this:

StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitNetwork().build();
StrictMode.setThreadPolicy(policy);

Answer 2

I've found the answer. For whatever reason, you have to use:

java.net.InetAddress[] x= java.net.InetAddress.getAllByName(Server.SERVERNAME) ; HelloWorldActivity.tv.setText("Address: "+x[0].getHostAddress());

Answer 3

It is strange that you have to do so. java.net.InetAddress.getByName works for me, out of the box.

There are some (on-going) issues related to DNS resolution in the Android emulator, so that might be it.

Answer 4

Don't know if it was a typo, but you said you have:

<use-permission id="android.permission.INTERNET" />

But it have to be:

<uses-permission android:name="android.permission.INTERNET" />

I tried getByName and it works fine.

May be you fixed your permissions and switched from getByName to getAllByName at the same time? Just curious, if you can confirm that getByName still does not work for you?