问题
I'm working on adding discovery to our app using (http://jmdns.sourceforge.net/). It's actually working correctly on my small home network. But it fails on the large network at the office. I seem to recall reading that if an app blocks for more than 5 seconds that it get's reset. And that appears to be what's happening. But first, how can I be sure that's actually the problem?
Of course, my main question is how can I can make JmDNS work on a large network. And the more general question is what do you do when you need more than 5 seconds?
Small snippet of my code (it's in an AsyncTask):
InetAddress bindingAddress = InetAddress.getByName(ipOfThisDevice);
jmdns = JmDNS.create(bindingAddress);
serviceList = Arrays.asList(jmdns.list("_myappname._tcp.local.",5000)); // 5 second timeout
回答1:
Here is the code I used in my Android app which you say seems to work at your office?
/*
ZeroConf Browser - http://melloware.com/
Copyright (C) 2010 Melloware Inc
All Rights Reserved.
*/
package com.melloware.zeroconf;
import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.TreeMap;
import javax.jmdns.JmDNS;
import javax.jmdns.ServiceEvent;
import javax.jmdns.ServiceInfo;
import javax.jmdns.ServiceListener;
import javax.jmdns.ServiceTypeListener;
import android.app.ExpandableListActivity;
import android.content.Context;
import android.net.wifi.WifiInfo;
import android.net.wifi.WifiManager;
import android.net.wifi.WifiManager.MulticastLock;
import android.os.Bundle;
import android.text.Html;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseExpandableListAdapter;
import android.widget.ImageView;
import android.widget.TextView;
/**
* Service tab which contains the expandable list of DNS Services and the details of each service type as they are
* gathered.
* <p>
* Copyright (c) 2010 Melloware, Inc. <http://www.melloware.com>
* @author Emil A. Lefkof III <info@melloware.com>
* @version 1.0
*/
public class ServiceActivity extends ExpandableListActivity implements ServiceListener, ServiceTypeListener {
/**
* Tag used for logging
*/
private static final String TAG = ServiceActivity.class.getName();
/**
* Value used to identify in ZeroConf
*/
private static final String HOSTNAME = "melloware";
/**
* Sorted array of top level items which are the Service Types
*/
public static final ArrayList<ServiceType> GROUPS = new ArrayList<ServiceType>();
/**
* Sorted list of the details for each service type
*/
public static final TreeMap<String, ArrayList<ServiceInfo>> DETAILS = new TreeMap<String, ArrayList<ServiceInfo>>();
/**
* Instance of Bonjour/Rendezvous/ZeroConf handler
*/
public static JmDNS jmdns = null;
/**
* Allows an application to receive Wifi Multicast packets.
*/
private static MulticastLock multicastLock = null;
/**
* The backing adapter for the ListView of services
*/
private static DNSExpandableListAdapter mAdapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mAdapter = new DNSExpandableListAdapter();
setListAdapter(mAdapter);
}
/*
* (non-Javadoc)
* @see android.app.Activity#onStart()
*/
@Override
protected void onStart() {
Log.i(TAG, "Starting ServiceActivity...");
super.onStart();
try {
Log.i(TAG, "Starting Mutlicast Lock...");
WifiManager wifi = (WifiManager) this.getSystemService(Context.WIFI_SERVICE);
// get the device ip address
final InetAddress deviceIpAddress = getDeviceIpAddress(wifi);
multicastLock = wifi.createMulticastLock(getClass().getName());
multicastLock.setReferenceCounted(true);
multicastLock.acquire();
Log.i(TAG, "Starting ZeroConf probe....");
jmdns = JmDNS.create(deviceIpAddress, HOSTNAME);
jmdns.addServiceTypeListener(this);
} catch (IOException ex) {
Log.e(TAG, ex.getMessage(), ex);
}
Log.i(TAG, "Started ZeroConf probe....");
}
/*
* (non-Javadoc)
* @see android.app.ActivityGroup#onStop()
*/
@Override
protected void onStop() {
Log.i(TAG, "Stopping ServiceActivity...");
super.onStop();
stopScan();
DETAILS.clear();
GROUPS.clear();
if (!isFinishing()) {
mAdapter.notifyDataSetChanged();
}
}
/**
* Stops scanning and cleans up locks.
*/
private static void stopScan() {
try {
if (jmdns != null) {
Log.i(TAG, "Stopping ZeroConf probe....");
jmdns.unregisterAllServices();
jmdns.close();
jmdns = null;
}
if (multicastLock != null) {
Log.i(TAG, "Releasing Mutlicast Lock...");
multicastLock.release();
multicastLock = null;
}
} catch (Exception ex) {
Log.e(TAG, ex.getMessage(), ex);
}
}
/**
* Gets the current Android device IP address or return 10.0.0.2 which is localhost on Android.
* <p>
* @return the InetAddress of this Android device
*/
private InetAddress getDeviceIpAddress(WifiManager wifi) {
InetAddress result = null;
try {
// default to Android localhost
result = InetAddress.getByName("10.0.0.2");
// figure out our wifi address, otherwise bail
WifiInfo wifiinfo = wifi.getConnectionInfo();
int intaddr = wifiinfo.getIpAddress();
byte[] byteaddr = new byte[] { (byte) (intaddr & 0xff), (byte) (intaddr >> 8 & 0xff), (byte) (intaddr >> 16 & 0xff), (byte) (intaddr >> 24 & 0xff) };
result = InetAddress.getByAddress(byteaddr);
} catch (UnknownHostException ex) {
Log.w(TAG, String.format("getDeviceIpAddress Error: %s", ex.getMessage()));
}
return result;
}
/**
* Delegate method from mDNS when a service is added.
*/
public void serviceAdded(ServiceEvent event) {
Log.i(TAG, String.format("ZeroConf serviceAdded(event=\n%s\n)", event.toString()));
ArrayList<ServiceInfo> list = DETAILS.get(event.getType());
if (list != null) {
ServiceInfo info = event.getInfo();
if (!list.contains(info)) {
list.add(info);
}
}
}
/**
* Delegate method from mDNS when a service is removed.
*/
public void serviceRemoved(ServiceEvent event) {
Log.w(TAG, String.format("ZeroConf serviceRemoved(event=\n%s\n)", event.toString()));
}
/**
* Delegate method from mDNS when a service is resolved.
*/
public void serviceResolved(ServiceEvent event) {
Log.i(TAG, String.format("ZeroConf serviceResolved(event=\n%s\n)", event.toString()));
ArrayList<ServiceInfo> list = DETAILS.get(event.getType());
if (list != null) {
ServiceInfo info = event.getInfo();
if (!list.contains(info)) {
list.add(info);
}
}
}
/**
* Delegate method from mDNS when a new service type is discovered.
*/
public void serviceTypeAdded(final ServiceEvent event) {
Log.i(TAG, String.format("ZeroConf serviceTypeAdded(event=\n%s\n)", event.toString()));
jmdns.addServiceListener(event.getType(), this);
runOnUiThread(new Runnable() {
public void run() {
final ServiceType type = new ServiceType();
type.setName(event.getType());
GROUPS.add(type);
Collections.sort(GROUPS);
DETAILS.put(event.getType(), new ArrayList<ServiceInfo>());
mAdapter.notifyDataSetChanged();
}
});
}
/**
* Delegate method from mDNS when a subtype is discovered.
*/
public void subTypeForServiceTypeAdded(ServiceEvent event) {
Log.i(TAG, String.format("ZeroConf subTypeForServiceTypeAdded(event=\n%s\n)", event.toString()));
}
/**
* When a scan is complete show a message if no services found.
* <p>
* @param context the ApplicationContext
*/
public static void scanFinished(Context context) {
if (GROUPS.size() == 0) {
final ServiceType type = new ServiceType();
type.setName(context.getResources().getString(R.string.msg_noservices));
GROUPS.add(type);
mAdapter.notifyDataSetChanged();
stopScan();
}
}
/**
* ExpandableListAdapter that displays the Service Types as groups and when each Service Type is expanded displays a
* list of all discovered Services for that Service Type.
*/
public class DNSExpandableListAdapter extends BaseExpandableListAdapter {
LayoutInflater inflater = LayoutInflater.from(getApplicationContext());
public Object getChild(int groupPosition, int childPosition) {
try {
Iterator<ArrayList<ServiceInfo>> it = DETAILS.values().iterator();
int i = 0;
while (it.hasNext()) {
ArrayList<ServiceInfo> type = it.next();
if (i == groupPosition) {
ServiceInfo service = type.get(childPosition);
ServiceInfo resolvedService = jmdns.getServiceInfo(service.getType(), service.getName());
if (resolvedService != null) {
service = resolvedService;
}
StringBuffer buf = new StringBuffer();
buf.append("<b>");
buf.append(service.getName());
buf.append("</b><br/>");
buf.append(service.getTypeWithSubtype());
buf.append("<br/>");
buf.append(service.getServer());
buf.append(':');
buf.append(service.getPort());
buf.append("<br/>");
buf.append(service.getInetAddresses()[0]);
buf.append("<br/>");
for (Enumeration<String> names = service.getPropertyNames(); names.hasMoreElements();) {
buf.append("<br/>");
String prop = names.nextElement();
buf.append("<b>");
buf.append(prop);
buf.append("</b>");
buf.append(" = ");
buf.append("<i>");
buf.append(service.getPropertyString(prop));
buf.append("</i>");
}
return buf.toString();
}
i++;
}
} catch (Exception e) {
Log.w("Exception", e);
}
return "Not Available";
}
public long getChildId(int groupPosition, int childPosition) {
return childPosition;
}
public int getChildrenCount(int groupPosition) {
Iterator<ArrayList<ServiceInfo>> it = DETAILS.values().iterator();
int i = 0;
while (it.hasNext()) {
ArrayList<ServiceInfo> type = it.next();
if (i == groupPosition) {
return type.size();
}
i++;
}
return 1;
}
public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
convertView = this.inflater.inflate(R.layout.child_row, parent, false);
((TextView) convertView.findViewById(R.id.childvalue)).setText(Html.fromHtml(getChild(groupPosition, childPosition).toString()));
return convertView;
}
public Object getGroup(int groupPosition) {
return GROUPS.get(groupPosition);
}
public int getGroupCount() {
return GROUPS.size();
}
public long getGroupId(int groupPosition) {
return groupPosition;
}
public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
convertView = this.inflater.inflate(R.layout.group_row, parent, false);
ServiceType type = (ServiceType) getGroup(groupPosition);
ImageView imageView = (ImageView) convertView.findViewById(R.id.serviceicon);
imageView.setImageResource(type.getImageIcon());
((TextView) convertView.findViewById(R.id.service)).setText(type.toString());
return convertView;
}
public boolean isChildSelectable(int groupPosition, int childPosition) {
return true;
}
public boolean hasStableIds() {
return true;
}
}
}
回答2:
Have a look at http://developer.android.com/training/connect-devices-wirelessly/nsd.html - that should get you started if you are running on Android
来源：https://stackoverflow.com/questions/18255329/how-to-make-jmdns-work-on-a-large-network