I opened a socket between an Android app and a python server. The combination is that the Server listens, and android connects to the Server.
Here is the server code. The problematic part takes place in the definition of handle :
import SocketServer
from time import sleep
import sys
HOST = '192.168.56.1'
PORT = 2000
class SingleTCPHandler(SocketServer.StreamRequestHandler):
def handle(self):
try:
while(1):
sleep(0.03)
data = self.rfile.readline().strip()
print data
except KeyboardInterrupt:
sys.exit(0)
class SimpleServer(SocketServer.ThreadingMixIn, SocketServer.TCPServer):
allow_reuse_address = True
def __init__(self, server_address, RequestHandlerClass):
SocketServer.TCPServer.__init__(self, server_address, RequestHandlerClass)
server = SimpleServer((HOST, PORT), SingleTCPHandler)
try:
server.serve_forever()
except KeyboardInterrupt:
sys.exit(0)
The connection is established normally, and the Android app sends the following data to the socket:
'0:0'
But the data is received on the Server as:
'\x000\x00:\x000\x00'
The variable that receives the data is:
data = self.rfile.readline().strip()
and printing gives the regular format:
In [2]: print data
0:0
I didn't manage to step into the print function with pdb to see what it does.
I'm looking for a way to convert the '\x000\x00:\x000\x00' to '0:0'.
Please advise on a way to convert the variable. You are welcome to comment/criticize the whole implementation. This is my first project in dealing with sockets so i don't know the pitfalls.
Update
This was the original Android code:
String podaci = "0:0";
public void Socketic() throws IOException {
Socket mojSocket = new Socket(urlServer, port);
DataOutputStream izlazdata = new DataOutputStream(
mojSocket.getOutputStream());
while (podaci != "end") {
try {
Thread.sleep(60);
} catch (InterruptedException e) {
e.printStackTrace();
}
izlazdata.writeChars(podaci);
izlazdata.flush();
}
izlazdata.close();
mojSocket.close();
};
And the problem was, as you suspected in:
izlazdata.writeChars(podaci);
writeChars uses the method writeChar. The API documentation for writeChar states:
Writes a char to the underlying output stream as a 2-byte value, high byte first...
The two bytes represent the 16bits which UTF-16 uses for encoding.
When we changed it to everything started working:
izlazdata.writeBytes(podaci);
Update
Based on the answers given, here is how the unwanted string is to be interpreted in terms of characters.
This solves my concrete problem, however, if someone would give a more generic solution to what happend here so that a larger lesson can be learned.
If not, i will accept Esailijas answer in a few days.
You need to show the code happening Android but it strongly seems like it's sending data in UTF-16BE. You should specify the encoding on the Android end. The characters are not hexadecimal literally, but because the NUL character is unprintable, python shows \x00 instead.
Another option is to decode it:
self.rfile.readline().decode("utf_16_be").strip()
note that the result of this is an unicode string.
Related
I'm building an app with the Entity Framework on Xamarin that lets me compare some data. But when I start my "fetchdata" function, I receive the Error:
System.Data.SqlClient.SqlException (0x80131904): Snix_Connect (provider: SNI_PN7, error: 35 - SNI_ERROR_35)Snix_Connect (provider: SNI_PN7, error: 35 - SNI_ERROR_35)
I see many posts about Xamarin / Android & that it is not possible to get a connection to a SQL Server. Is there any way to fetch data from a SQL Server with .NET Core on Xamarin?
This is the string I put into SQL_Class folder with Sql_Common.cs
Fill up the brace brackets with actual parameters (removing the brace brakets too).
public static string SQL_connection_string = #"data source={server_address};initial catalog={database_name};user id={user_id};password={password};Connect Timeout={seconds}";
Then I access whenever I need it from any xamarin code just like we use in our asp.net c#
This works for me on my app without any issues.
using (SqlConnection Sql_Connection = new SqlConnection(Sql_Common.saralEHR_connection_string))
But as #Jason mentioned in his first reply, I too would get once again check the security part. I fexperienced before publishing Package to Google Play, they encrypt the App files with Hash Key Code and then only it gets upload to server
Yes it is possible (HuurrAYY!):
Im new in .net core, c# and so on and for me it was a hell of a work to get it working..
So here for the other noobs who are seeking for Help:
Guide´s i used:
Building Android Apps with Entity Framework
https://medium.com/#yostane/data-persistence-in-xamarin-using-entity-framework-core-e3a58bdee9d1
https://blog.xamarin.com/building-android-apps-entity-framework/
Scaffolding
https://cmatskas.com/scaffolding-dbcontext-and-models-with-entityframework-core-2-0-and-the-cli/
How i did it:
Build your normal Xamarin app.
create new .net solution like in the tutorials (DONT WRITE YOUR Entity Framework CLASSES)
create a third solution what has to be a .net core console application
Scaffold your DB in your CONSOLE application move all created classes & folders in your "xamarin .net" solution & change the namespaces
Ready to Go!
Side Node: NuGets you need in every solution:
Microsoft.EntityFrameworkCore
Microsoft.EntityFrameworkCore.SqlServer
[EDIT: NuGets you need in every solution]
I am doing this way (working snippet):
string connectionString = #"data source={server};initial catalog={database};user id={user};password={password};Connect Timeout=10";
string databaseTable = "{table name}";
string selectQuery = String.Format("SELECT count(*) as Orders FROM {0}", databaseTable);
try
{
using (SqlConnection connection = new SqlConnection(connectionString))
{
//open connection
connection.Open();
SqlCommand command = new SqlCommand(selectQuery, connection);
command.Connection = connection;
command.CommandText = selectQuery;
var result = command.ExecuteScalar().ToString();
//check if there is result
if(result != null)
{
OrdersLabel.Text = result;
}
}
}
catch (Exception ex)
{
OrdersLabel.Text = ex.Message;
}
It is working fine, but API call more elegant.
I hope it helps.
I am facing a strange issue, and I am not able to debug it out. I have implemented a logic for uploading stream of data and am using Volley for the same, I have customized a logic little bit in HurlStack, addBodyIfExists api,so that body of type "application/octet-stream" can be handled.
My logic is to post progress to user, so that UI can be updated indicating user progress in upload, below my logic for same.
int toRead = length; // File length
byte[] data = new byte[4096];
connection.setDoOutput(true);
if(length != -1) {
connection.setFixedLengthStreamingMode(length);
} else {
connection.setChunkedStreamingMode(4096);
}
OutputStream os;
int i;
int count;
os = connection.getOutputStream();
int progress= 0;
try {
for(i = 0; (count= is.read(data)) > 0; ++i) { // is, is not null and contains a valid input stream
os.write(data, 0, count); // at this line am getting unexpected end of stream
progress+= count;
if(i % 20 == 0) {
rs.deliverProgress(progress, 0L);
progress= 0;
}
}
os.flush();
} finally {
if(is != null) {
is.close();
}
if(os != null) {
os.close();
}
}
on executing above code am getting this, although I have verified, output stream is not null, neither do input stream, it fails in first iteration of read loop itself, am seeing it has read 4096 bytes and then trying to write the same.
java.net.ProtocolException: unexpected end of stream
at com.android.okhttp.internal.http.HttpConnection$FixedLengthSink.close(HttpConnection.java:326)
at com.android.okio.RealBufferedSink.close(RealBufferedSink.java:174)
at com.android.okio.RealBufferedSink$1.close(RealBufferedSink.java:142)
any help in debugging above will he highly appreciated.
This may help you :
That exception is thrown by FixedLengthInputStream when the expected number of bytes (usually set in the content-length header of the response) is larger than the actual data in the response.
Check that the content-length header is correct. (If you're supplying your own value for the content length, make sure it is correct.)
It would help to see your code that sets up the input stream.
Already Fixed it, please add "Accept-Encoding", "identity" in header, then the server-side will get command that it will not modify the response, then send back to Clients.
If you have checked everywhere in your code and tried every solution in stackoverflow and github but the issue still occurs, and you have only tested your code on emulator, then, you should try to run your code on your real device instead. Maybe it will work, or maybe it won't, but if you feel desperate, just have a try, seriously. I was astonished when I happened to find that my code ran with bugs on emulator everytime but successfully on my mobile phone. Besides, the code also ran sucessfully on others' android emulators. So I guess there is something wrong in my android studio configuration that I can't find out. I have no idea why this happen, just like we don't know why "Clean Project/Invalidate caches" sometimes works better than any solution.
It is a little strange that your data length might be unknown.
Is it a media file? Or a live stream?
Anyway, I tried to upload my live stream data. And it happened in the same error.
I added this setting to the Connection and solved my problem.
Transfer-Encoding : chunked
("setChunkedStreamingMode" didn't work. I still don't know why.)
This happens for me on android emulator and doesn't happen on my physical android device.
I was doing GET request to flask server running on 0.0.0.0 on my laptop from the android app.
To fix it on the emulator, add the servers ip address in the emulators proxy.
see How to set up Android emulator proxy settings
The exact problem i had was unexpected end of stream retrofit
I am programming an authentication service in Android and this one includes a server part written in java.
I do the same operations in both parts executing these two pieces of codes in Android and Server:
ANDROID:
String genChallengeResponse(String challenge, String message) {
String Hmac_ALG = "HmacSHA256";
SecretKey key = new SecretKeySpec(challenge.getBytes(), Hmac_ALG);
Mac m = Mac.getInstance(Hmac_ALG);
m.init(key);
m.update(password.getBytes());
byte[] mac = m.doFinal();
return new String(Base64.encode(mac, Base64.DEFAULT));
}
SERVER:
String genChallengeResponse(String challenge, String message) {
String Hmac_ALG = "HmacSHA256";
SecretKey key = new SecretKeySpec(challenge.getBytes(), Hmac_ALG);
Mac m = Mac.getInstance(Hmac_ALG);
m.init(key);
m.update(password.getBytes());
byte[] mac = m.doFinal();
return new String(Base64.encodeBase64(mac));
}
Starting from the same challenge and message these are the results:
Android: n2EaLpQr0uKgkZKhCQzwuIFeeLjzZKerZcETVNcfla4=
Server: n2EaLpQr0uKgkZKhCQzwuD9eeLjzZKerZcETVNcfla4=
^^
These are different just for TWO CHARACTERS.
The problem is that this strange behaviour does not appear in every pair of String passed to the functions...
I tried to use the UTF-8 in each system, but nothing changes...
Do someone knows what is the problem? If this is a known problem...
(is important to say that the problem is the same using Android 2.2 or also 4.0, then the problem is not the operating system, I think).
Can't comment yet therefore as answer:
I found out a few weeks ago that Android's Base64 uses different settings for the Linefeeds (check here: http://developer.android.com/reference/android/util/Base64.html )
I think in my case it was NO_WRAP missing.Perhaps one of the other options (NO_PADDING or URL-Safe, does the tested password contain + or - ?) could change your results...
I'm using JDOM with my Android project, and every time I get a certain set of characters in my server response, I end up with these error messages:
05-04 10:08:46.277: E/PARSE: org.jdom.input.JDOMParseException: Error on line 95 of document UTF-8: At line 95, column 5263: unclosed token
05-04 10:08:46.277: E/Error Handler: Handler failed: org.jdom.input.JDOMParseException: Error on line 1: At line 1, column 0: syntax error
When I make the same query through google chrome, I can see that all of the XML came through fine, and that there are in fact no areas where a token is not closed. I have run into this problem several times throughout the development of the application, and the solution has always been to remove odd ascii characters (copyright logos, or trademark characters, etc. that got copied/pasted into those data fields). How can I get it to either a remove those characters, or b strip them and continue the function. Here's an example of one of my parse functions.
public static boolean parseUserData(BufferedReader br) {
SAXBuilder builder = new SAXBuilder();
Document document = null;
try {
document = builder.build(br);
/* XML Output to Logcat */
if (document != null) {
XMLOutputter outputter = new XMLOutputter(
Format.getPrettyFormat());
String xmlString = outputter.outputString(document);
Log.e("XML", xmlString);
}
Element rootNode = document.getRootElement();
if (!rootNode.getChildren().isEmpty()) {
// Do stuff
return true;
}
} catch (Exception e) {
GlobalsUtil.errorUtil
.setErrorMessage("Error Parsing XML: User Data");
Log.e(DEBUG_TAG, e.toString());
return false;
}
}
It distinctly sounds like a character encoding issue. I think duffymo is correct in his assessment. I have two comments though ....
If you are getting your data through a URL you should be using the URLConnection.getContentType() to get the charset (if it is set and the charset is not null) to set up the InputStreamReader on the URL's InputStream...
Have you tried JDOM 2.0.1? It is the first JDOM version that is fully tested on Android... (and the only 'supported' JDOM version on Android). JDOM 2.0.1 also has a number of performance tweaks, and memory optimizations that should make your processing faster. It also fixes a number of bugs.... though from what I see you should not run in to any bug problems.....
Check out https://github.com/hunterhacker/jdom/wiki/JDOM2-Migration-Issues and https://github.com/hunterhacker/jdom/wiki/JDOM2-and-Android
Is the BufferedReader constructed to take the encoding argument? Perhaps you need to tell the Reader or InputStream that you pass to use UTF-8.
I've been trying all day to make this thing works but it's still not right yet. I've checked so many posts around here and tested so many different implementations that I'dont know where to look now...
Here is my situation, I have a small php test file (gz.php) on my server wich looks like this :
header("Content-Encoding: gzip");
print("\x1f\x8b\x08\x00\x00\x00\x00\x00");
$contents = gzcompress("Is it working?", 9);
print($contents);
This is the simplest I could do and it works fine with any web browser.
Now I have an Android activity using Jsoup that has this code :
URL url = new URL("http://myServerAdress.com/gz.php");
doc = Jsoup.parse(url, 1000);
Which cause an empty EOFException on the "Jsoup.parse" line.
I've read everywhere that Jsoup is supposed to parse gzipped content without having to do anything special, but obviously, there's something missing.
I've tried many other ways like using Jsoup.connect().get() or InpuStream, GZipInputStream and DataInpuStream. I did try the gzDeflate() and gzencode() methods from PHP as well but no luck either. I even tried not to declare the header-encoding in PHP and try to deflate the content later...but it was as clever as effective...
It has to be something "stupid" I'm missing but I just can't tell what... anybody has an idea?
(ps : I'm using Jsoup 1.7.0, so the latest one as of now)
The asker indicated in a comment that gzcompress was writing a CRC that was both incorrect and incomplete, according to information from here, the operative code being:
// Display the header of the gzip file
// Thanks ck#medienkombinat.de!
// Only display this once
echo "\x1f\x8b\x08\x00\x00\x00\x00\x00";
// Figure out the size and CRC of the original for later
$Size = strlen($contents);
$Crc = crc32($contents);
// Compress the data
$contents = gzcompress($contents, 9);
// We can't just output it here, since the CRC is messed up.
// If I try to "echo $contents" at this point, the compressed
// data is sent, but not completely. There are four bytes at
// the end that are a CRC. Three are sent. The last one is
// left in limbo. Also, if we "echo $contents", then the next
// byte we echo will not be sent to the client. I am not sure
// if this is a bug in 4.0.2 or not, but the best way to avoid
// this is to put the correct CRC at the end of the compressed
// data. (The one generated by gzcompress looks WAY wrong.)
// This will stop Opera from crashing, gunzip will work, and
// other browsers won't keep loading indefinately.
//
// Strip off the old CRC (it's there, but it won't be displayed
// all the way -- very odd)
$contents = substr($contents, 0, strlen($contents) - 4);
// Show only the compressed data
echo $contents;
// Output the CRC, then the size of the original
gzip_PrintFourChars($Crc);
gzip_PrintFourChars($Size);
Jonathan Hedley commented, "jsoup just uses a normal Java GZIPInputStream to parse the gzip, so you'd hit that issue with any Java program." The EOFException is presumably due to the incomplete CRC.