I perform some large downloads. I start a download being connected to 3G, all is fine. Then, I switch to WiFi connection, but the request returns a timeout exception. I have used HttpClient library. I have implemented a retry mechanism, so, when the request returns an exception, it sleeps for 0.5 seconds and tries to execute again and again. I would expect that, after connecting to a WiFi, the Http request could execute. But it seems that the Http execute method returns a null response, all the time after that. Very strange, if I commute again to 3G, the execute method returns again a good response. Can anyone help me please :) ?
First, it seems that it may be more convenient to use DownloadManager for large files - it handles retry and everything.
As for HttpClient - it's known to have some issues, but i'm not sure if you bumped into one of them or just overlooked something. It's been deprecated as of Gingerbread, you may want to try HttpUrlConnection instead, it's said to have less problems than HttpClient.
Also, when switching between WIFI and cell connections, HttpClient may need to be reinitialized completely, there's http range header to tell server which byte you want to continue downloading from. But again, I suggest you give DownloadManager a try, it may save you a lot of time.
This might be a routing problem:
when switching between different network types usually the local ip address and, more important, the local routing table changes, due to a different gateway being used. This means that packages that traveled fine between client and server wont reach any destination after a network change, if they are send the same route. Most likely your client implementation has to be notified of the change or even restartet completely, so that the routing strategy is reinitilized.
If the documentation of the implementation components you use dont reveal anything you could try to track this down using a package sniffer like wireshark. Typically packages running into nirwhana show up easily there.
Related
In my Android app, I do poll a device (Wallbox) every 5 seconds using the Volley library. For one customer, I get
java.net.NoRouteToHostException: Address not available
after several hours. Usually, using the exactly same type of device and at my place, this polling works for days, but not at (at least) this customer.
The device address is on the local LAN.
I have not found any description about "address not available" that might apply to my case, or at least I did not see the point.
The call is always the same:
http://192.168.160.152/api/status
As this is live data, I set ".setShouldCache(false)" for the request.
Meanwhile, other HTTP requests (in this case, a query to a WWW address, also polled continuously), even using Volley, continue to work:
https://backend.powerfox.energy/api/2.0/my/***********/current
The connection works again after rebooting the device (and at the same original IP address), so I guess it has nothing to do with the wallbox or the router.
And if the wallbox would be not available, I assue I would get "unreachable" error or such.
Is there someone who can help me, what could cause that exception ("address not available"), and what can I do about it?
i am trying to develop a cordova(3.5.0) project in android platform and in that i have to check network connection availability before each API call. for that i am using 'navigator.connection.type',and some times it return 0. why this is happening? plz help me for solving this trouble
Without some more details I can only guess.. There are some conditions which may cause this.
navigator.connection.type = 0 -> connection type unknown.
So you may have a connection, you may not it simply hasn't been determined yet, or because of privileges the device isn't saying.
Are you calling this check too early? ie before deviceready
In our app we do not check the connection each time but we handle it this way:
by making the API request anyway, knowing that its possible to fail, we set a timeout and error handling. If it fails by error or timeout we check connection type and then ping the server with a simple "hello" "acknowledge" request. Its a super small request that we figure will work or if it timeouts again the connection must be so poor it might as well be disconnected.
This is because there are really two types of connection you need to check. Many miss this!
And also because its navigator totally lies some times... :/
Just because wifi is on and connected and navigator tells you this, it doesn't mean you will have a connection to the outside world. You need to check the network hardware (which is all navigator will tell you) but you must also check network connectivity, if this is something you are sensitive about.
I am using the class HttpUrlConnection for requesting JSON responses
I realized that no matter if I set or not
System.setProperty("http.keepAlive", "false");
The first response is always going to take longer, while the next responses are very quick, with and without keepAlive. I am not even using SSL.
Notice that, my app doesn't need to perform any authentication with the server, so there isn't any startup call to the webservices. The first request I make to the webservices is actually the very first.
I am also verifying server-side with "netstat", that by setting keepAlive false on the Android client the connections disappear straight away, while without specifying keepAlive false they keep staying as "ESTABLISHED".
How can you explain that subsequent responses are quicker even if the connection doesn't persist?
ANDROID CODE:
line 1) URL url = new URL(stringUrl);
line 2) HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
line 3) InputStream instream = new BufferedInputStream(urlConnection.getInputStream());
Until line 2 everything always gets executed very quickly, either with keepAlive or not. Line 3 in the first request takes around 3 seconds, while in all subsequent always less than 1 second. Each request is about 0.5KB gzipped.
SYSTEM:
I am testing using a Nexus 5, connected via 3G
My webservices are written in Go, running on a CentOS 6.4 linux server
I am using standard tcp v4
UPDATE:
For the moment I have decided to use a trick: when the fragment is resuming, I make a HTTP HEAD request to the server. In this way all subsequent calls in the next 10 seconds are very quick. If the user waits more than 10 seconds then the first one will be slow, and the next ones will be quick again. This is all happening without using KeepAlive.
It's a really big mistery now. It looks like there is some kind of "awake" period which lasts for about 10 seconds. I don't think there is anything strange on my code which can result on that. Also because everything seems to happen during the line 3 I reported above.
SOLVED! thanks to Mark Allison!
Here is a very clear explanation:
http://developer.android.com/training/efficient-downloads/efficient-network-access.html
Also, everything can easily be monitored using Android DDMS's Network Statistics. If you wait some seconds (let's say 20) from last request, you can see that it takes 2 seconds to transmit a new request.
I suspect that the lag that you are seeing is simply down to the cellular radio transitioning from either low power or idle state to full power (which can take over 2 seconds).
Check out Reto Meier's excellent DevBytes series on Efficient Data Transfer for an in-depth explanation of what's going on.
The first request cannot leverage a keep-alive obviously, because thankfully Android doesn't keep the connections alive for minutes or hours. Only subsequent requests can reuse keep-alive connections and only after a short period of time.
It's natural that you have to wait in line 3. Before something like conn.getResponseCode() or conn.getInputStream() the HttpURLConnection is in CREATED state. There is no network activity until it's getting in CONNECTED state. Buffered* shouldn't make any difference here.
I've observed long delays when using SSL and there was a time-shift between server and device. This happens very often when using an emulator which is not cold-booted. For that I've a small script running before test. It's important that PC and emulator are in the same time-zone, otherwise it's very contra-productive: (see below, because it's hard to show the command inline).
I can imagine that Android saves battery in putting 3G into sleep mode when there is no activity. This is just speculation, but you could make a test by creating some other network activity with other apps (browser, twitter, ...) and then see whether your app needs the same long "think time" until first connection.
There are other good options for losing time: DNS resolution, Server-side "sleep" (e.g. a virtual machine loading "memory" from disk).
The command to set time of Android emulator:
adb -e shell date -s `date +"%Y%m%d.%H%M%S"`
Edit
To further analyze the problem, you could run tcpdump on your server. Here is tutorial in case you don't know it well. Store the dumps to files (pcap) and then you can view them with wireshark. Depending on the traffic on your CentOS server you have to set some filters so you only record the traffic from your Android device. I hope that this gives some insight to the problem.
To exclude your server from being the bad guy, you could create a small script with curl commands doing the equivalent as your app.
You could create a super-tiny service without database or other i/o dependencies and measure the performance. I don't know "Go", but the best thing would be a static JSON file delivered by Apache or nginx. If you only have Go, then take something like /ping -> { echo "pong" }. Please tell us your measurements and observations.
Instead of using so many classes I suggest you use this library
you can have a look at here
http://loopj.com/android-async-http/
your code will become very very less , instead of declaring so many classes writing bulk of code , you can just use 4 lines of code
AsyncHttpClient client = new AsyncHttpClient();
client.get("http://www.google.com", new AsyncHttpResponseHandler() {
#Override
public void onSuccess(String response) {
System.out.println(response);
}
});
It is very efficient in geting the response very quickly(1 or 2 secs including parsing).
I hope this will help you out. :)
I am building an android app that exchanges data with our server through http api calls. In many cases users are complaining that the app is slow or doesn't work at all.
The most common cause of that is bad network connectivity (low 3g/wifi signal or congested public wifi).
What is the best way to detect bad connections? Once i can detect bad connectivity an icon or toast message can be used to inform the user about the situation.
I am using HttpUrlConnection for the api calls.
I think you can make use of ConnectivityManager. Call getActiveNetworkInfo() and then call getDetailedState() on the NetworkInfo object received. You can check the state of the connection and whether it is VERIFYING_POOR_LINK, though I don't know in which conditions this state is active.
Also you might want to listen to network changes as described in Detect Connection Changes.
I'd probably use latency. Save the time when you get the request, and when the request finishes. If you're seeing numbers that are too high, pop up the warning. If you're downloading large files, you may wish to switch to throughput (how many kbps you're transfering).
as far as i remember http is "connectionless"..
you should try concentrating on minimizing the size of your traffic.. (compress, divide.. etc)
if you really want to test connectivity i guess you should do pings.. every x seconds.. then if the ping is bad you could warn the user..
My app needs to contact the same device it is working on, via http://127.0.0.1/... (a localhost url).
For some reason, about 50% of the times (and maybe exactly 50%) when I reach a website there with JSON content, I get the exception:
java.net.SocketException: recvfrom failed: ECONNRESET (Connection reset by peer)
For the other 50%, I get perfectly good results. I've tried to do polls (and even large delay between polls), but I keep getting the same weird results.
I've searched the internet and also here, and I'm not sure why it occurs. Does the peer mean that the client has caused it? Why does it happen, and how should i handle it?
Some websites say that it's a common thing, but I didn't find what's the best thing to do in such cases.
Ok, the answer was that it's the server's fault - it had to close the connection after each request.
It might be that Android keeps a pool of connections and use the old one or something like that.
Anyway , now it works.
EDIT: according to the API of HttpURLConnection, this can be solved on the client side too:
The input and output streams returned by this class are not buffered.
Most callers should wrap the returned streams with BufferedInputStream
or BufferedOutputStream. Callers that do only bulk reads or writes may
omit buffering. When transferring large amounts of data to or from a
server, use streams to limit how much data is in memory at once.
Unless you need the entire body to be in memory at once, process it as
a stream (rather than storing the complete body as a single byte array
or string).
To reduce latency, this class may reuse the same underlying Socket for
multiple request/response pairs. As a result, HTTP connections may be
held open longer than necessary. Calls to disconnect() may return the
socket to a pool of connected sockets. This behavior can be disabled
by setting the http.keepAlive system property to false before issuing
any HTTP requests. The http.maxConnections property may be used to
control how many idle connections to each server will be held.
Taken from:
developer.android.com/reference/java/net/HttpURLConnection.html
Try to set this property for your HttpURLConnection before connecting:
conn.setRequestProperty("connection", "close");
This will disable "keep-alive" property which is on by default.
This is an old thread i know. But this might help someone.
In my case this error was caused by the .NET WCF (soap) service. One of the objects in the returning result had a DataMember with get{} property but no set{} property.
For serialization to occur every DataMember should have both get{} & set{} available. I implemented an empty set{} (empty due to my business rules), and problem was solved.
My scenerio is a specific bad server implementation, but maybe it'll help someone saving time when troubleshooting.
I was having a lot of these Connection reset by peer when I was visiting certain web pages or downloading files (from my app or the Android browser).
Turned out it was my 3G carrier that blocked the connections (e.g. downloading an .exe file was forbidden).
Do you have the same problem on Wifi ?
in my situation the problem has been solved by cleaning the proxy address and port from APN which was produced by the operator.
as I have tested, using IP address of remote server instead of domain name also can solve the problem.
In our case the issue is in the Server side (Application Pool configuration in IIS). I resolved it by setting Maximum Worker Processes to 1. Setting it with value more than 1 will enable Web Garden which seems to be the issue.