Android :: WiFi Disconnected When Phone In Sleep Mode?

I have a service which polls a server at certain intervals. I use an AlarmManager and a BroadcastReceiver to start the service. My problem is that after a certain duration, even though the WiFi is still enabled, but for some reason, my application can't contact the server. I get an "Unreachable network" error. Note that I've already acquired a partial wake lock as well as a wifilock. Here's my code for the BroadcastReceiver.

public class ServiceAlarmBroadcastReceiver extends BroadcastReceiver {
public void onReceive(Context context, Intent intent) {
WakeLock wakeLock = null; WifiLock wifiLock = null;
try { PowerManager pm = (PowerManager) context .getSystemService(Context.POWER_SERVICE);
// acquire a WakeLock to keep the CPU running
wakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "MyWakeLock");
if(!wakeLock.isHeld()){ wakeLock.acquire();
} Log.i("ServiceAlarmBroadcastReceiver", "WakeLock acquired!");
WifiManager wm = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
wifiLock = wm.createWifiLock(WifiManager.WIFI_MODE_FULL , "MyWifiLock");
if(!wifiLock.isHeld()){ wifiLock.acquire();
} Log.i("ServiceAlarmBroadcastReceiver", "WifiLock acquired!");
context.startService(new Intent(context, ThePollerService.class));
} finally { // release the WakeLock to allow CPU to sleep
if (wakeLock != null) { if (wakeLock.isHeld()) {
wakeLock.release(); Log.i("ServiceAlarmBroadcastReceiver", "WakeLock released!");
} } // release the WifiLock if (wifiLock != null) { if (wifiLock.isHeld()) { wifiLock.release();
Log.i("ServiceAlarmBroadcastReceiver", "WiFi Lock released!"); } } } } }