We Keep Coding

How to encapsulate a SCTP packet in UDP and send it over UDP channel in java

I have to transfer a file using SCTP protocol. I have written the code in java but the code is not working when I am using 4G hotspot network. So I came across this RFC which talks about UDP encapsulation of SCTP. I want to know if there is an implementation which I can use to encapsulate SCTP packet in UDP and send it over UDP channel so that it can traverse heavily NATted network. My current code for sending the data packet is as follows:
import java.io.*;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.util.*;
import com.sun.nio.sctp.MessageInfo;
import com.sun.nio.sctp.SctpChannel;
import com.sun.nio.sctp.SctpServerChannel;
public class Main {
SctpChannel connectionChannelPrimary;
SctpChannel connectionChannelSecondary;
InetSocketAddress serverSocketAddressPrimary;
InetSocketAddress serverSocketAddressSecondary;
String directoryPath;
public Main() {
serverSocketAddressPrimary = new InetSocketAddress(6002);
serverSocketAddressSecondary = new InetSocketAddress(6003);
}
public void setDirectoryPath(String directoryPath) {
this.directoryPath = directoryPath;
}
public String getDirectoryPath() {
return directoryPath;
}
public void establishConnection(int connId) throws IOException {
SctpServerChannel sctpServerChannel = SctpServerChannel.open();
if (connId == 0) {
sctpServerChannel.bind(serverSocketAddressPrimary);
connectionChannelPrimary = sctpServerChannel.accept();
System.out.println("connection established for primary");
} else {
sctpServerChannel.bind(serverSocketAddressSecondary);
connectionChannelSecondary = sctpServerChannel.accept();
System.out.println("connection established for helper");
}
}
ArrayList<String> getAllFiles() {
File directory = new File(this.directoryPath);
ArrayList<String> fileNames = new ArrayList<>();
for (File fileEntry : Objects.requireNonNull(directory.listFiles())) {
if (fileEntry.isFile()) {
fileNames.add(fileEntry.getName());
}
}
Collections.sort(fileNames);
return fileNames;
}
public byte[] readFile(String filename) throws IOException {
String extraString = "\n\n\n\nNRL\n\n\n";
File file = new File(filename);
FileInputStream fl = new FileInputStream(file);
ByteBuffer finalBuffer = ByteBuffer.allocate((int) (file.length() + extraString.length()));
byte[] arr = new byte[(int) file.length()];
int res = fl.read(arr);
if (res < 0) {
System.out.println("Error in reading file");
fl.close();
return null;
}
fl.close();
finalBuffer.put(arr);
finalBuffer.put(extraString.getBytes());
byte[] tmp = new byte[extraString.length()];
finalBuffer.position((int) (file.length() - 1));
finalBuffer.get(tmp, 0, tmp.length);
return finalBuffer.array();
}
public void sendBytes(String filename, int connId) throws IOException {
byte[] message = readFile(filename);
assert message != null;
System.out.println(message.length);
int tmp = 0;
int cntIndex = 60000;
int prevIndex = 0;
boolean isBreak = false;
while (!isBreak) {
byte[] slice;
if (prevIndex + 60000 >= message.length) {
slice = Arrays.copyOfRange(message, prevIndex, message.length);
isBreak = true;
} else {
slice = Arrays.copyOfRange(message, prevIndex, cntIndex);
prevIndex = cntIndex;
cntIndex = cntIndex + 60000;
}
final ByteBuffer byteBuffer = ByteBuffer.allocate(64000);
final MessageInfo messageInfo = MessageInfo.createOutgoing(null, 0);
byteBuffer.put(slice);
byteBuffer.flip();
tmp += slice.length;
try {
if (connId == 0) connectionChannelPrimary.send(byteBuffer, messageInfo);
else connectionChannelSecondary.send(byteBuffer, messageInfo);
} catch (Exception e) {
e.printStackTrace();
}
}
System.out.println(tmp);
}
public static void main(String[] args) throws IOException {
String bgFilePath = "/home/iiitd/Desktop/background/";
String fgFilePath = "/home/iiitd/Desktop/foreground/";
Main myObj = new Main();
myObj.setDirectoryPath("/home/iiitd/Desktop/tmp/");
myObj.establishConnection(1);
myObj.establishConnection(0);
ArrayList<String> files = myObj.getAllFiles();
for (String tmpFile : files) {
String cntFilePath = myObj.getDirectoryPath() + tmpFile;
myObj.sendBytes(cntFilePath,0);
}
}
}
RFC Link: https://datatracker.ietf.org/doc/html/draft-ietf-tsvwg-sctp-udp-encaps-09

In C, I think that usrsctp is a popular implementation of SCTP over UDP. If I understand correctly, it was used by Google Chrome at some point (though I see they mentioned moving to "dcsctp" at some point). Also I have seen it in a mirror of the Firefox sources in 2016, not sure what's the state today.
So one solution would be to wrap usrsctp with JNI. And it appears that this is exactly what jitsi-sctp is doing. I haven't used it, but I would have a look.

Code works fine on JAVA But Fails to Create Decrypted File on Android

I was trying to make a file File Locker App for Android. For encryption & Decryption I used some code which I previously tested on JAVA. It works fine on JAVA, But Fails to Create The Decrypted File on Android platform.
My Code is something like bellow,
public class Cryptographer {
private static final String ALGORITHM = "AES";
private final static String ALGO_RANDOM_NUM_GENERATOR = "SHA1PRNG";
public static int encrypt(String key, File inputFile, File outputFile)
throws CryptographyException {
if(!outputFile.getParentFile().exists())outputFile.getParentFile().mkdir();
return StartCryptography(Cipher.ENCRYPT_MODE, key, inputFile, outputFile);
}
public static int decrypt(String key, File inputFile, File outputFile)
throws CryptographyException {
if(!outputFile.getParentFile().exists())outputFile.getParentFile().mkdir();
return StartCryptography(Cipher.DECRYPT_MODE, key, inputFile, outputFile);
}
private static int StartCryptography(int cipherMode, String key, File inputFile,
File outputFile) throws CryptographyException {
int performance = -1;
try {
SecureRandom random = SecureRandom.getInstance(ALGO_RANDOM_NUM_GENERATOR);
random.setSeed(key.getBytes());
KeyGenerator generator = KeyGenerator.getInstance(ALGORITHM);
generator.init(random);
SecretKey key1 = generator.generateKey();
Cipher cipher = Cipher.getInstance(ALGORITHM);
cipher.init(cipherMode, key1);
FileInputStream inputStream = new FileInputStream(inputFile);
byte[] inputBytes = new byte[(int) inputFile.length()];
inputStream.read(inputBytes);
byte[] outputBytes = cipher.doFinal(inputBytes);
FileOutputStream outputStream = new FileOutputStream(outputFile);
outputStream.write(outputBytes);
inputStream.close();
outputStream.close();
performance = 1;
} catch (NoSuchPaddingException | NoSuchAlgorithmException
| InvalidKeyException | BadPaddingException
| IllegalBlockSizeException | IOException ex) {
throw new CryptographyException("Error encrypting/decrypting file", ex);
} finally {
return performance;
}
}
}
I am using a button which when pressed All Files From a declared Array Should First be encrypted, and then the encrypted file will be decrypted to another location. But no Decrypted file is created.
My onClick Method of the button looks like bellow,
public void onKeyDown1(View view) throws CryptographyException {
File outfile = new File(ExternalStorageDirectoryPath, "Encrypted");
File outfileDec = new File(ExternalStorageDirectoryPath, "Decrypted");
for (MyFiles f : files) {
if (f.getCheckstate()) {
File EncFile=new File(outfile,f.getName());
//File DecFile=new File(outfileDec,f.getName());
Cryptographer.encrypt(key, f, EncFile);
Cryptographer.decrypt(key, EncFile, DecFile);
}
}
}
Someone please help me..!!
The ExternalStorageDirectoryPathis a String retrieved by Calling Environment.getExternalStorageDirectory().getAbsolutePath(); .
And MyFiles Class is
public class MyFiles extends File {
boolean Checkstate=false;
public MyFiles(File dir, String name) {
super(dir, name);
}
public MyFiles(String path) {
super(path);
}
public MyFiles(String dirPath, String name) {
super(dirPath, name);
}
public MyFiles(URI uri) {
super(uri);
}
public void setCheckstate(boolean checkstate) {
Checkstate = checkstate;
}
public boolean getCheckstate(){
return Checkstate;
}
public MyFiles[] listFiles(FileFilter filter) {
MyFiles[] files = listFiles();
if (filter == null || files == null) {
return files;
}
List<MyFiles> result = new ArrayList<MyFiles>(files.length);
for (MyFiles file : files) {
if (filter.accept(file)) {
result.add(file);
}
}
return result.toArray(new MyFiles[result.size()]);
}
public MyFiles[] listFiles() {
return filenamesToFiles(list());
}
private MyFiles[] filenamesToFiles(String[] filenames) {
if (filenames == null) {
return null;
}
int count = filenames.length;
MyFiles[] result = new MyFiles[count];
for (int i = 0; i < count; ++i) {
result[i] = new MyFiles(this, filenames[i]);
}
return result;
}
}

I suppose it might be lack of permissions in Manifest file of your android app. Check: http://developer.android.com/guide/topics/manifest/manifest-intro.html
Or you are trying to write in a location your app is not allowed

Changing normal application to thread in java [closed]

Closed. This question needs to be more focused. It is not currently accepting answers.
Want to improve this question? Update the question so it focuses on one problem only by editing this post.
Closed 8 years ago.
Improve this question
I have to change my basic application into threads
my application behaviour
read the files from a folder
Get extensions from the file
through if else condition checks whether it belongs to (doc,ppt,pptx) & does the operation
After processing it will starts from step 1.
can you tell me how to proceed since i'm new to threads
I dont need entire code i need just steps to follow
(like in which area i can use thread)
thanks in advance

I did something like this long before. Sorting jpeg,pdf, png, mp3 files to different folders using threads. I used the magic number of files for identifying rather than using the extension.
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStreamReader;
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
/**
*
* #author Zac
*/
public class Sorting extends Thread{
private static final int MAGIC_PNG[] = new int[] { 0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a };
private static final int MAGIC_JPG[] = new int[] { 0xFF, 0xD8, 0xFF };
private static final int MAGIC_PDF[] = new int[] { 0x25, 0x50, 0x44, 0x46 };
private static final int MAGIC_MP3[] = new int[] { 0x49, 0x44, 0x33 };
private String stagingDirectory,targetDirectory,preferenceFileDir;
private File thePrefs;
public Sorting(){
preferenceFileDir = System.getProperty( "user.home" );
thePrefs = new File(preferenceFileDir+"/Staging/prefs.txt");
}
private static boolean isPng(File filename) throws Exception {
FileInputStream ins = new FileInputStream(filename);
try {
for(int i = 0; i < MAGIC_PNG.length; ++i) {
if(ins.read() != MAGIC_PNG[i]) {
return false;
}
}
return true;
} finally {
ins.close();
}
}
private static boolean isJpg(File filename) throws Exception {
FileInputStream ins = new FileInputStream(filename);
try {
for(int i = 0; i < MAGIC_JPG.length; ++i) {
if(ins.read() != MAGIC_JPG[i]) {
return false;
}
}
return true;
} finally {
ins.close();
}
}
private static boolean isMp3(File filename) throws Exception {
FileInputStream ins = new FileInputStream(filename);
try {
for(int i = 0; i < MAGIC_MP3.length; ++i) {
if(ins.read() != MAGIC_MP3[i]) {
return false;
}
}
return true;
} finally {
ins.close();
}
}
private static boolean isPdf(File filename) throws Exception {
FileInputStream ins = new FileInputStream(filename);
try {
for(int i = 0; i < MAGIC_PDF.length; ++i) {
if(ins.read() != MAGIC_PDF[i]) {
return false;
}
}
return true;
} finally {
ins.close();
}
}
private void getPreference(){
FileInputStream fis = null;
try{
fis = new FileInputStream(thePrefs);
BufferedReader br = new BufferedReader(new InputStreamReader(fis));
stagingDirectory= br.readLine();
targetDirectory = br.readLine();
}
catch(Exception e){
}
}
public void run() {
//System.out.print("in run \n");
int len;
getPreference();
File stDir = new File(stagingDirectory);
File[] listOfFiles = stDir.listFiles();
//System.out.print(listOfFiles);
if(listOfFiles == null)
len =0;
else
len = listOfFiles.length;
try{
while(true){
System.out.println(len);
for(int i = 0;i<len;i++){
if(isJpg(listOfFiles[i])){
System.out.println(listOfFiles[i].getName()+ " is jpeg");
listOfFiles[i].renameTo(new File(targetDirectory+"/jpeg/"+listOfFiles[i].getName()+".jpeg"));
}
else if(isPdf(listOfFiles[i])){
System.out.println(listOfFiles[i].getName()+ " is pdf");
listOfFiles[i].renameTo(new File(targetDirectory+"/pdf/"+listOfFiles[i].getName()+".pdf"));
}
else if(isMp3(listOfFiles[i])){
System.out.println(listOfFiles[i].getName()+ " is mp3");
listOfFiles[i].renameTo(new File(targetDirectory+"/mp3/"+listOfFiles[i].getName()+".mp3"));
}
else if(isPng(listOfFiles[i])){
System.out.println(listOfFiles[i].getName()+ " is png");
listOfFiles[i].renameTo(new File(targetDirectory+"/png/"+listOfFiles[i].getName()+".png"));
}
}
listOfFiles = stDir.listFiles();
len = listOfFiles.length;
Thread.sleep(3000);//sleeps for 3 seconds
}
}catch(Exception e){
System.out.println("interrupted"+e);
}
}
}
In my public static void main(String[] args)
obj= new Sorting();
obj.start(); //calls the run method
here's the github link for the project.
Sorting out files using java
Hope it helps. Project was done in netbeans / java 1.7

Java: accessing a List of Strings as an InputStream

Is there any way InputStream wrapping a list of UTF-8 String? I'd like to do something like:
InputStream in = new XyzInputStream( List<String> lines )

You can read from a ByteArrayOutputStream and you can create your source byte[] array using a ByteArrayInputStream.
So create the array as follows:
List<String> source = new ArrayList<String>();
source.add("one");
source.add("two");
source.add("three");
ByteArrayOutputStream baos = new ByteArrayOutputStream();
for (String line : source) {
baos.write(line.getBytes());
}
byte[] bytes = baos.toByteArray();
And reading from it is as simple as:
InputStream in = new ByteArrayInputStream(bytes);
Alternatively, depending on what you're trying to do, a StringReader might be better.

You can concatenate all the lines together to create a String then convert it to a byte array using String#getBytes and pass it into ByteArrayInputStream. However this is not the most efficient way of doing it.

In short, no, there is no way of doing this using existing JDK classes. You could, however, implement your own InputStream that read from a List of Strings.
EDIT: Dave Web has an answer above, which I think is the way to go. If you need a reusable class, then something like this might do:
public class StringsInputStream<T extends Iterable<String>> extends InputStream {
private ByteArrayInputStream bais = null;
public StringsInputStream(final T strings) throws IOException {
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
for (String line : strings) {
outputStream.write(line.getBytes());
}
bais = new ByteArrayInputStream(outputStream.toByteArray());
}
#Override
public int read() throws IOException {
return bais.read();
}
#Override
public int read(byte[] b) throws IOException {
return bais.read(b);
}
#Override
public int read(byte[] b, int off, int len) throws IOException {
return bais.read(b, off, len);
}
#Override
public long skip(long n) throws IOException {
return bais.skip(n);
}
#Override
public int available() throws IOException {
return bais.available();
}
#Override
public void close() throws IOException {
bais.close();
}
#Override
public synchronized void mark(int readlimit) {
bais.mark(readlimit);
}
#Override
public synchronized void reset() throws IOException {
bais.reset();
}
#Override
public boolean markSupported() {
return bais.markSupported();
}
public static void main(String[] args) throws Exception {
List source = new ArrayList();
source.add("foo ");
source.add("bar ");
source.add("baz");
StringsInputStream<List<String>> in = new StringsInputStream<List<String>>(source);
int read = in.read();
while (read != -1) {
System.out.print((char) read);
read = in.read();
}
}
}
This basically an adapter for ByteArrayInputStream.

You can create some kind of IterableInputStream
public class IterableInputStream<T> extends InputStream {
public static final int EOF = -1;
private static final InputStream EOF_IS = new InputStream() {
#Override public int read() throws IOException {
return EOF;
}
};
private final Iterator<T> iterator;
private final Function<T, byte[]> mapper;
private InputStream current;
public IterableInputStream(Iterable<T> iterable, Function<T, byte[]> mapper) {
this.iterator = iterable.iterator();
this.mapper = mapper;
next();
}
#Override
public int read() throws IOException {
int n = current.read();
while (n == EOF && current != EOF_IS) {
next();
n = current.read();
}
return n;
}
private void next() {
current = iterator.hasNext()
? new ByteArrayInputStream(mapper.apply(iterator.next()))
: EOF_IS;
}
}
To use it
public static void main(String[] args) throws IOException {
Iterable<String> strings = Arrays.asList("1", "22", "333", "4444");
try (InputStream is = new IterableInputStream<String>(strings, String::getBytes)) {
for (int b = is.read(); b != -1; b = is.read()) {
System.out.print((char) b);
}
}
}

In my case I had to convert a list of string in the equivalent file (with a line feed for each line).
This was my solution:
List<String> inputList = Arrays.asList("line1", "line2", "line3");
byte[] bytes = inputList.stream().collect(Collectors.joining("\n", "", "\n")).getBytes();
InputStream inputStream = new ByteArrayInputStream(bytes);

You can do something similar to this:
https://commons.apache.org/sandbox/flatfile/xref/org/apache/commons/flatfile/util/ConcatenatedInputStream.html
It just implements the read() method of InputStream and has a list of InputStreams it is concatenating. Once it reads an EOF it starts reading from the next InputStream. Just convert the Strings to ByteArrayInputStreams.

you can also do this way create a Serializable List
List<String> quarks = Arrays.asList(
"up", "down", "strange", "charm", "top", "bottom"
);
//serialize the List
//note the use of abstract base class references
try{
//use buffering
OutputStream file = new FileOutputStream( "quarks.ser" );
OutputStream buffer = new BufferedOutputStream( file );
ObjectOutput output = new ObjectOutputStream( buffer );
try{
output.writeObject(quarks);
}
finally{
output.close();
}
}
catch(IOException ex){
fLogger.log(Level.SEVERE, "Cannot perform output.", ex);
}
//deserialize the quarks.ser file
//note the use of abstract base class references
try{
//use buffering
InputStream file = new FileInputStream( "quarks.ser" );
InputStream buffer = new BufferedInputStream( file );
ObjectInput input = new ObjectInputStream ( buffer );
try{
//deserialize the List
List<String> recoveredQuarks = (List<String>)input.readObject();
//display its data
for(String quark: recoveredQuarks){
System.out.println("Recovered Quark: " + quark);
}
}
finally{
input.close();
}
}
catch(ClassNotFoundException ex){
fLogger.log(Level.SEVERE, "Cannot perform input. Class not found.", ex);
}
catch(IOException ex){
fLogger.log(Level.SEVERE, "Cannot perform input.", ex);
}

I'd like to propose my simple solution:
public class StringListInputStream extends InputStream {
private final List<String> strings;
private int pos = 0;
private byte[] bytes = null;
private int i = 0;
public StringListInputStream(List<String> strings) {
this.strings = strings;
this.bytes = strings.get(0).getBytes();
}
#Override
public int read() throws IOException {
if (pos >= bytes.length) {
if (!next()) return -1;
else return read();
}
return bytes[pos++];
}
private boolean next() {
if (i + 1 >= strings.size()) return false;
pos = 0;
bytes = strings.get(++i).getBytes();
return true;
}
}

Java Large file to be saved in database - Object design

I am trying to figure out object design to implement large file(~600 MB) respository in the Database using hibernate.
Please suggest a correct approach/design?
class ModelClass{
String name; //meta data
...
Option 1.
byte[] file; // dont want to load the content of the entire file
// in memory by using this but hibernate recognizes
// this datatype
Option 2.
InputStream inputStream;
OutputStream outputStream;
// I can have the methods to provide the input or output stream
// but i dont think its a clean approach. I am not sure how
// I will be able to work with hibernate with streams
Option 3.
File fileHandle;
}
Any other options??
I would like to call save(Object) method of hibernateTemplate to save the object in Database. Dont know if I should have just the meta-data in the class and handle the file save and retreive seperately.
Thanks in advance.
Another workable solution is to use "Work" Interface. The purpose was to avoid loading the file content into memory.
session.doWork(new Work(){
#Override
public void execute(Connection conn) {
//direct sql queries go here
}
});

I have written a SerializableFile class that keeps data in a file. When the object is read, it creates a temporary file.
Here it is:
public class SerializableFile implements Serializable {
private static final File TEMP_DIR = getTempDir();
private transient boolean temporary;
private transient String name;
private transient File file;
public SerializableFile() {
}
public SerializableFile(File file) {
this.file = file;
this.name = file.getName();
this.temporary = false;
}
#Override
protected void finalize() throws Throwable {
dispose();
super.finalize();
}
public void dispose() {
if (temporary && file != null) {
file.delete();
file = null;
}
}
public File keep(String name) throws IOException {
if (temporary) {
temporary = false;
} else {
File newFile = new File(TEMP_DIR, name);
keepAs(newFile);
file = newFile;
}
return file;
}
public void keepAs(File outFile) throws IOException {
if ((temporary || file.equals(outFile)) && file.renameTo(outFile)) {
temporary = false;
file = outFile;
} else {
InputStream in = new FileInputStream(file);
try {
OutputStream out = new FileOutputStream(outFile);
try {
byte buf[] = new byte[4096];
for (int n = in.read(buf); n > 0; n = in.read(buf)) {
out.write(buf, 0, n);
}
} finally {
out.close();
}
} finally {
in.close();
}
outFile.setLastModified(file.lastModified());
}
}
public String getName() {
return name;
}
public File getFile() {
return file;
}
public long lastModified() {
return file.lastModified();
}
private void writeObject(ObjectOutputStream out) throws IOException {
int size = (int)file.length();
long date = file.lastModified();
out.writeUTF(name);
out.writeInt(size);
out.writeLong(date);
InputStream in = new FileInputStream(file);
try {
byte buf[] = new byte[4096];
while (size > 0) {
int n = in.read(buf);
if (n <= 0 || n > size) {
throw new IOException("Unexpected file size");
}
out.write(buf, 0, n);
size -= n;
}
} finally {
in.close();
}
}
private void readObject(ObjectInputStream in) throws IOException {
name = in.readUTF();
int size = in.readInt();
long date = in.readLong();
file = File.createTempFile("tmp", ".tmp", TEMP_DIR);
OutputStream out = new FileOutputStream(file);
try {
byte buf[] = new byte[4096];
while (size > 0) {
int n = in.read(buf, 0, size <= buf.length ? size : buf.length);
if (n <= 0 || n > size) {
throw new IOException("Unexpected file size");
}
out.write(buf, 0, n);
size -= n;
}
} finally {
out.close();
}
file.setLastModified(date);
temporary = true;
}
private static File getTempDir() {
File dir;
String temp = System.getProperty("com.lagalerie.live.temp-dir");
if (temp != null) {
dir = new File(temp);
} else {
String home = System.getProperty("user.home");
dir = new File(home, "temp");
}
if (!dir.isDirectory() && !dir.mkdirs()) {
throw new RuntimeException("Could not create temp dir " + dir);
}
return dir;
}
}

Open JPA supports a #Persistent annotation with some databases:
MySQL
Oracle
PostgreSQL
SQL Server
DB2

Even if you are still using an RDBMS as a data store, you should consider storing this binary data into a file system, and saving the directory / location of the path into the database, instead of storing this as a BLOB or CLOB into the database.