Develop Reference

UnknownHostException on Android native https GET against a Cloudflare Webserver (Non-Cloudflare webservers work)

I get this error when trying to make a HTTP GET on https://bot.whatismyipaddress.com/
My code:
public void dostuff(){
...
targeturl = "https://bot.whatismyipaddress.com/";
response = _makeSimpleHttpRequest(targeturl, "GET", "");
...
}
public static String _makeSimpleHttpRequest(String targetUrl, String methodGetPostX, String postBody) throws MalformedURLException, IOException, NotImplementedException{
String responseline = "";
String temp = "";
HttpURLConnection httpConn = null;
InputStream inputStream = null;
InputStreamReader inputStreamReader = null;
BufferedReader bufferedReader = null;
OutputStream outputStream = null;
OutputStreamWriter outputStreamWriter = null;
BufferedWriter bufferedWriter = null;
try {
java.net.URL url = null;
url = new java.net.URL(targetUrl); // system default DNS resolver
httpConn = (HttpURLConnection)url.openConnection(); // HERE THE ERROR OCCURED
...
}
The error:
W/System.err: java.net.UnknownHostException: Unable to resolve host "bot.whatismyipaddress.com": No address associated with hostname
at java.net.Inet6AddressImpl.lookupHostByName(Inet6AddressImpl.java:156)
at java.net.Inet6AddressImpl.lookupAllHostAddr(Inet6AddressImpl.java:103)
at java.net.InetAddress.getAllByName(InetAddress.java:1152)
at com.android.okhttp.Dns$1.lookup(Dns.java:41)
at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:178)
at com.android.okhttp.internal.http.RouteSelector.nextProxy(RouteSelector.java:144)
at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:86)
at com.android.okhttp.internal.http.StreamAllocation.findConnection(StreamAllocation.java:176)
at com.android.okhttp.internal.http.StreamAllocation.findHealthyConnection(StreamAllocation.java:128)
at com.android.okhttp.internal.http.StreamAllocation.newStream(StreamAllocation.java:97)
at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:289)
at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:232)
W/System.err: at com.android.okhttp.internal.huc.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:465)
at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:411)
at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:248)
at com.android.okhttp.internal.huc.DelegatingHttpsURLConnection.getInputStream(DelegatingHttpsURLConnection.java:211)
at com.android.okhttp.internal.huc.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:30)
at mypackage.utils.CommonUtils._makeSimpleHttpRequest(CommonUtils.java:251)
at mypackage.utils.CommonUtils._makeSimpleHttpRequest(CommonUtils.java:293)
at mypackage.utils.CommonUtils.lambda$isNetworkAvailable$0(CommonUtils.java:77)
at mypackage.utils.-$$Lambda$CommonUtils$I9O8EFeqOM7bNsVQ5uILro0gOxg.call(Unknown Source:4)
at com.google.android.gms.tasks.zzy.run(com.google.android.gms:play-services-tasks##17.2.0:2)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:929)
Caused by: android.system.GaiException: android_getaddrinfo failed: EAI_NODATA (No address associated with hostname)
at libcore.io.Linux.android_getaddrinfo(Native Method)
at libcore.io.ForwardingOs.android_getaddrinfo(ForwardingOs.java:74)
at libcore.io.BlockGuardOs.android_getaddrinfo(BlockGuardOs.java:200)
at libcore.io.ForwardingOs.android_getaddrinfo(ForwardingOs.java:74)
at java.net.Inet6AddressImpl.lookupHostByName(Inet6AddressImpl.java:135)
... 24 more
I changed DNS resolver to a self implemented DNS resolver. On the android device bot.whatismyipaddress.com can not be resolved. However whatismyipaddress.com is resolved correctly to a ipv4 address. With windows commandline i get the same result:
nslookup whatismyipaddress.com
Server: fritz.box
Address: 192.168.178.1
Nicht autorisierende Antwort:
Name: whatismyipaddress.com
Addresses: 2606:4700::6810:9b24
2606:4700::6810:9a24
104.16.154.36
104.16.155.36
>>
>>
nslookup bot.whatismyipaddress.com
Server: fritz.box
Address: 192.168.178.1
Name: bot.whatismyipaddress.com
(----- no Addresses! ----)
>>
>>
Previously it worked in the browser (both on phone and on PC). However after a few tries the browser got blocked aswell. The browser went through while the android native and nslookups failed already.
I changed the URL to another cloudflare server checkip.dyndns.org which resulted in the same result. The android native HTTP-GET calls failed during DNS lookup instantly. The browser failed after a while.
I changed to a non-cloudflare server ipinfo.io/ip which went through correctly.
I guess cloudflare webserver doesn't like the native android DNS resolver (or nslookup)... Maybe some kind of DDOS protection? Does anyone have an idea how to make a simple HTTP-GET to a cloudflare webserver from android without beeing blocked? I already tried alternating SSL Unsafe and the ip of the topdomain. However i think the problem is already in the DNS-Resolver step before performing any http calls... Thank you for a hint!
Device Huawei P30 pro VOG-L29 Android 10.1.0 Build 10.1.0.161(c431e23r2p5), problem exists both on WIFI and on mobile Data

I think you may be extrapolating too much that this is an issue with Cloudflare or being blocked. A quick search of your first service results in a notice that they have shut it down (probably due to high usage) -
As of November 10, 2021 we are no longer providing this API due to massive abuse.
https://whatismyipaddress.com/api
Your other services could be experiencing similar issues with reliability. Server security wouldn't really cause DNS lookup to fail. Luckily there are many, many, alternatives you can try. For example -
https://www.ipify.org/
Or Cloudflare even has an (undocumented) endpoint that could be used -
https://www.cloudflare.com/cdn-cgi/trace
At the end of the day though, if you want something reliable / guaranteed, you'll probably have to pay for it. Otherwise be prepared to shift to a new service every so often. Luckily the data returned should be easy to integrate (an IP address).

Server java app not working on a local connection

hi have at home a rasperry pi running a server java app, connected to de router with the dynamic DNS configured and the in/out communication ports openned.
When i run the android apication client througt 4g everithing is working sucessfull. But when i run the same app connected to the wifi on my local net, where the server are running, the server application looks like death.
Any ideas?
Thanks.
router config

I think the problem is related to your DNS. If you are connected using your wifi, you have to return a local IP-Address. Do you have any chance of configuring your router to return the raspberries local IP-Address for wifi-clients?
Take a look here: link

A simple solution, even if it is not very elegant, is adding the following conditions to your code:
If there is an error connecting to the Dyn DNS, try to connect to the local IP address. (In case you are in the Wifi LAN)
If the local IP address fails, try again your Dyn DNS (in case the user is a real user with real communication problems)
(repeat until the connection is successful)
You can also identify your testing devices (using Settings.Secure.ANDROID_ID, or the IMEI) and use the local IP only for them. Another option is making the URL configurable (with a hidden option for example).

Because of my app can run local, only needs to connect to server for updates. I have block the connection on the server app if the ip from client and server are equals.
At the moment is the best solution to keep the server app running properly.
URL whatismyip = new URL("http://checkip.amazonaws.com");
BufferedReader in = new BufferedReader(new
InputStreamReader(whatismyip.openStream()));
String ip = in.readLine();
try {
SSLServerSocketFactory sslFactory = (SSLServerSocketFactory)SSLServerSocketFactory.getDefault();
SSLServerSocket ss = (SSLServerSocket) sslFactory.createServerSocket(PORT);
int idSession = 0;
while (true) {
SSLSocket socket = (SSLSocket)ss.accept();
if(socket.getInetAddress().getHostAddress().equals(ip)){
if (socket != null && !socket.isClosed()) {
socket.close();
}
}
((ServidorThread) new ServidorThread(socket, idSession)).start();
idSession++;
}
} catch (IOException ex) {
ex.printStackTrace(System.out);
Logger.getLogger(Servidor.class.getName()).log(Level.SEVERE, null, ex);
}
}

How to Check whether an IP is reachable or not, in codename one

We have sockets here to get the host / IP of the device.
How to check whether the URL host is reachable or not?
Just as we do in Java or android with Inet Address.

InetAddress.getByName(ip).isReachable(timeout);

To check connection to an http server you can use something like:
ConnectionRequest r = new ConnectionRequest();
r.setUrl(serverUrl);
r.setTimeout(5000);
r.setFailSilently(true);
NetworkManager.getInstance().addToQueueAndWait(r);
if(r.getResponseCode() != 200) {
// no connection...
}

Can't connect through WiFi, but possible through Mobile Data

I've a php file named test.php stored in my Openshift server (http://phpgear-shifz.rhcloud.com/v1/test.php) with the below code.
<?php
echo "Hello";
Task
I am trying to download the text from an Android application.
Problem
I am getting a java.net.UnknownHostException: Unable to resolve host "phpgear-shifz.rhcloud.com": No address associated with hostname while connecting through a WiFi network, but everything is fine with Mobile Data.
Android Activity Code
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test);
final TextView tvTest = (TextView) findViewById(R.id.tvTest);
new AsyncTask<Void, Void, String>() {
#Override
protected String doInBackground(Void... params) {
try {
final URL url = new URL("http://phpgear-shifz.rhcloud.com/v1/test.php");
final BufferedReader br = new BufferedReader(new InputStreamReader(url.openStream()));
final StringBuilder sb = new StringBuilder();
String line;
while((line = br.readLine())!=null){
sb.append(line).append("\n");
}
br.close();
return sb.toString();
} catch (IOException e) {
e.printStackTrace();
return "Error: " + e.getMessage();
}
}
#Override
protected void onPostExecute(String result) {
tvTest.setText(result);
}
}.execute();
}
RESPONSES
on WiFi
on Mobile Data
Question
1) Why I can't connect through the WiFi network where Mobile Data is perfectly fine ?
2) How to solve this problem ?
NOTE: Sometime it's getting connected, sometime won't.

Your DNS doesn't know the IP address of the requested site.
You are experiencing problems, because the DNS of your Wifi connection cannot convert a hostname to an IP address.
And your data carrier is using different DNS which has associated IP address to hostname.
Try to change your DNS server address on your Wifi router or use direct IP address of the website if available.
Here are some google DNS server addresses
8.8.8.8
8.8.4.4

You may have an IPv4 vs IPv6 problem. Many mobile data plans use IPv6, while most WiFi installations currently use IPv4, so you may be switching more than just the network layer; you may actually be switching layer 3 protocols.
The DNS entry for phpgear-shifz.rhcloud.com points to an IPv4 address (only), so it should work on WiFi. But maybe your mobile device uses an IPv6 DNS server and can't resolve the name via IPv4?
Another possibility: your mobile device may have a more general problem in the IPv4 stack. Your mobile data may be using one of the 6-to-4 transition technologies and thus bypass your local IPv4 problem.
I noticed another problem with the DNS name phpgear-shifz.rhcloud.com although I doubt it is related.
That DNS entry is actually a CNAME entry that points to another CNAME entry, which in turn points to an A record on Amazon. Double indirections of CNAMEs are a violation of the DNS RFCs, although most resolver should handle it anyway. Also, if this was the problem, it should affect both WiFi and mobile data equally.

Android connection to localhost

I'm trying to connect my android application to a local host url thanks to wamp server but it doesn't work. My goal here, is to fetch json data and parse these data. For my test, i'm using a device not the emulator and i use permission in AndroidManifest.xml :
<uses-permission android:name="android.permission.INTERNET" />
My url looks like this :
String url = "http://10.0.2.2:8080/tests/PhpProject1/connectionBDD.php";
i tried :
http://localhost/
http://10.0.2.2:8080/
http://10.0.2.2/
But it never worked so far :
java.net.ConnectException: failed to connect to localhost/127.0.0.1 (port 80): connect failed: ECONNREFUSED (Connection refused)
failed to connect to /10.0.2.2 (port 8080): connect failed: ETIMEDOUT (Connection timed out)
java.net.ConnectException: failed to connect to /10.0.2.2 (port 80): connect failed: ETIMEDOUT (Connection timed out)
Then i tried with a json url test found on the internet : http://headers.jsontest.com/
It worked really good and i got json data at this address. So i guess my code is good and the issue here is my localhost url, i don't know what should be its exact form..
I read many threads about it but i didn't find a solution.
Here my code :
Main activity :
public class MainActivity extends Activity {
private String url = "http://10.0.2.2:8080/tests/PhpProject1/connectionBDD.php";
private ListView lv = null;
private Button bGetData;
#Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final JsonDownloaderTask task = new JsonDownloaderTask(this);
lv = (ListView) findViewById(R.id.list);
bGetData = (Button)findViewById(R.id.getdata);
bGetData.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
task.execute(url);
}
});
}
public void jsonTaskComplete(JSONArray data){
//todo
}
}
AsyncTask :
public class JsonDownloaderTask extends AsyncTask<String, String, JSONArray> {
MainActivity ma;
public JsonDownloaderTask(MainActivity main){
ma = main;
}
#Override
protected JSONArray doInBackground(String... url) {
JSONParser jParser = new JSONParser();
// Getting JSON from URL
JSONArray jsonArray = null;
try {
jsonArray = jParser.getJSONFromUrl(url[0]);
} catch (IOException e) {
e.printStackTrace();
}
return jsonArray;
}
protected void onPostExecute(JSONArray data){
ma.jsonTaskComplete(data);
}
}
JSONParser :
public class JSONParser {
String data = "";
JSONArray jsonArray = null;
InputStream is = null;
public JSONParser(){}
// Method to download json data from url
public JSONArray getJSONFromUrl(String strUrl) throws IOException{
try{
URL url = new URL(strUrl);
// Creating an http connection to communicate with url
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
is = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
StringBuffer sb = new StringBuffer();
String line = "";
while( ( line = br.readLine()) != null){
sb.append(line);
}
is.close();
data = sb.toString();
//br.close();
jsonArray = new JSONArray(data);
}catch(Exception e){
Log.d("Exception while downloading url", e.toString());
}finally{
is.close();
}
return jsonArray;
}
}

IP-address 10.0.2.2 is used to fetch data from the emulator.
Localhost will always point to the emulator/android device running the application.
To let your device fetch data from your pc, it should be in the same network (connected by WiFi to your router) and you should use the local IP-address of your pc (normally a 192.168.1.x-number).

If you try to connect to "localhost", it will resolve to the Android device, not to your own localhost (unless you are running within the emulator). What I recommend for development is to add an overflow menu in the action bar that has an entry named "Settings" that provides a Settings activity for specifying application settings, and to have a "Developer options" entry in "Settings" that lets you specify a custom server address to use. During development, you can use this option to enter a custom server address for your app. (You will need a real server address that is actually reachable over the Internet rather than using localhost for this).

First you have to bind the IP address of the machine where your server is running in the eclipse settings.
You can do this like this.
Right click on the PHP project in the eclipse then Run Configuration then In the Web Application where you will find the Argument tab. Now here give the port and LAN IP address of your machine on which your server is running.
Something like this --port=8888 --address=192.168.1.6 then update the URL to http://192.168.1.6:8080/tests/PhpProject1/connectionBDD.php
Here in my case this is my LAN IP address 192.168.1.6, there you will have to find it using the network command like ipconfig , ifconfig and use that IP address.

if you are using your phone instead of emulator and running services on localhost then in url instead of '10.0.2.2' use IP address of your PC.

I solved it by:
1. Adding another android permission in the manifest: "android.permission.ACCESS_NETWORK_STATE"
2. As I'm using xampp, I've shared the xampp folder of the desktop in the network.
3. The xampp is running in a desktop whose ip is 192.168.x.x so the webservice's url instead of beign "http://localhost/myapi..." is "http://192.168.x.x/myapi..."
I tested the app using the emulator and also in a device. Both cases works out.

One simple way i know is keep mobile data on and share wifi . Connect your laptop or computer to this wifi . Now see ip of ur laptop or desktop. Call service from ur phone . Since your phone and your computer are in same network now.

I assume you are trying to access web service available on your PC from either an android simulator or a real device.
For an android emulator, you must NOT just use "localhost", because "localhost" means android emulator itself, NOT the host PC.
you need modify the /etc/hosts file or the simulator or real device. add a line like "192.168.0.100 service.local".

I tried "10.0.2.2:80/mysitename/page.php"
Miracle happened, it's working now.
I am on Mac and using XAMPP for server.
You can change port no. to 80 and try.
port 8080 was not working for me!
Cheers.

Just Install the "conveyor by Keyoti" the extension in Visual studio and it will generate a url according to your ip address automatically. here's the link:
conveyor
so far so good....!