In my app, i'm sending a file from a client, using sockets. On the other side, another client receive the file using InputStream and then bufferedOutputStream save the file in the system.
I don´t know why, the file isn´t utterly transmited. I think this is because of network overload, anyway, i don´t know how to solve it.
Transmiter is:
Log.d(TAG,"Reading...");
bufferedInputStream.read(byteArrayFile, 0, byteArrayFile.length);
Log.d(TAG, "Sending...");
bufferedOutputStream.write(byteArrayFile,0,byteArrayFile.length);
bufferedOutputStream.flush();
Receiver is:
bufferedOutputStream=new BufferedOutputStream(new FileOutputStream(file));
byteArray=new byte[fileSize];
int currentOffset = 0;
bytesReaded = bufferedInputStream.read(byteArray,0,byteArray.length);
currentOffset=bytesReaded;
do {
bytesReaded = bufferedInputStream.read(byteArray, currentOffset, (byteArray.length-currentOffset));
if(bytesReaded >= 0){ currentOffset += bytesLeidos;
}
} while(bytesReaded > -1 && currentOffset!=fileSize);
bufferedOutputStream.write(byteArray,0,currentOffset);
You don't state where filesize came from, but there are numerous problems with this code. Too many to mention. Throw it all away and use DataInputStream.readFully(). Or use the following copy loop, which doesn't require a buffer the size of the file, a technique which does not scale, assumes that the file size fits into an int, and adds latency:
byte[] buffer = new byte[8192];
int count;
while ((count = in.read(buffer)) > 0)
{
out.write(buffer, 0, count);
}
Use this at both ends. If you're sending multiple files via the same connection it gets more complex, but you haven't stated that.
Related
I am sending files between 2 devices, so I established a socket communication. Right now, I am just trying to send one file, but in the future I want to send multiple files (selected by the user from a gridview).
The problem is that when I send one file, on the server side (that receives the file) the socket.getInputStream().read(buffer) does not detect the end of the file. It just waits for "more" data to be sent.
After searching a bit on this issue, I reached some topics that kind of gave me some options, but I am still not satisfied with it because I dont know if those options would be efficient to send multiple files. This is an example : How to identify end of InputStream in java
I could close the socket or the stream objects after sending a file, but if I want to send a lot of files, it wouldn't be efficient to be always closing and opening the sockets.
Code on the receiver :
File apkReceived = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS) + "/testeReceiveServerComm.apk");
byte[] buffer = new byte [8192];
FileOutputStream fos=new FileOutputStream(apkReceived);
int count=0;
int total=0;//so apra ir vendo quanto recebi.
while((count = in.read(buffer)) != -1){
fos.write(buffer,0,count);
total+=count;
System.out.println("Server Comm receive thread - already received this ammount : "+total);
}
Code on the client (sender) :
File apkToSend=new File(filePath);
byte[] buffer = new byte [8192];
BufferedInputStream bis=new BufferedInputStream(new FileInputStream(apkToSend));
int count;
int total=0;
while((count=bis.read(buffer))!=-1){
out.write(buffer,0,count);
total+=count;
out.reset();
System.out.println("send thread - already sent this ammount : "+total);
}
out.flush();
bis.close();
I am building an android app, we build a socket to transfer file from this end to another end.
The file is sent through computer (when we test it on the computer), it works very well.
But when we build app to android, and send file from this android to another android through the socket that we put on a computer (used as server) so the received file is missing (file size is not enough). Sometime it is enough, but sometime is not enough, but almost time it is NOT enough.
It totally works very well on PC when testing.
Hope you guys have some ideas to help me.
This is my code:
1/ Code at Java server application - send file:
int countBufferReceive = 0;
byte[] buffer = new byte[1024 * 1024];
int numByte = 0;
while ((numByte = this.receiveStream.read(buffer, 0, buffer.length)) > 0) {
client.sendStream.write(buffer, 0, numByte);
client.sendStream.flush();
countBufferReceive += numByte;
if (countBufferReceive == fileLength)
break;
}
2/ Code at Android app - receive file:
int countBufferReceive = 0;
byte[] buffer = new byte[1024 * 1024];
int numByte = 0;
while ((numByte = ConnectServer.receiveStream.read(buffer, 0, buffer.length)) > 0) {
fos.write(buffer, 0, numByte);
fos.flush();
countBufferReceive += numByte;
if (countBufferReceive == fileLength)
break;
}
fos.close();
Thank you,
I've implemented a custom BackupAgent and part of my data are images which are about 1 MB large. When creating the backup, every image is written as a separate entity. On restoring the images, I wanted to read the data in 4K (BUFFER_SIZE) chunks like this and write it to a file like this:
FileOutputStream out = new FileOutputStream(file);
byte[] buffer = new byte[BUFFER_SIZE];
int offset = 0;
int n = 0;
// readEntityData returns 0 when all data of entity is read
while (0 != (n = data.readEntityData(buffer, offset, BUFFER_SIZE))) {
out.write(buffer, 0, n);
offset += n;
}
However, this only reads the first 4K chunk correctly, on the second call of readEntityData an IOException with error code 0xffffffff is thrown.
When I make the buffer as large as the entity's data size and read all the data at once, it works perfectly, but I think it would be safer to use a smaller buffer.
Has anybody experienced something like that? All examples I found read the data at once and not in multiple chunks.
Since my problem is close to this one, I haven been looing at feedbacks from this possible solution : Reading on a NetworkStream = 100% CPU usage but I fail to find the solution I need.
Much like in this other question, I want to use something else than an infinite while loop.
More precisely, I am using Xamarin to build Android application in Visual Studio. Since I need a Bluetooth service I am using a Stream to read and send data.
Reading data from Stream.InputStrem is where I have a problem : is there some sort of a blocking call to wait for data to be available without using a while (true) loop ?
I tried :
Begin/End Read
Task.Run and await
Here is a code sample:
public byte[] RetrieveDataFromStream()
{
List<byte> packet = new List<byte>();
int readBytes = 0;
while (_inputStream.CanRead && _inputStream.IsDataAvailable() && readBytes < 1024 && _state == STATE_CONNECTED)
{
try
{
byte[] buffer = new byte[1];
readBytes = _inputStream.Read(buffer, 0, buffer.Length);
packet.Add(buffer[0]);
}
catch (Java.IO.IOException e)
{
return null;
}
}
return packet.ToArray();
}
I call this method from a while loop.
This loop will check until this method returns something else than NULL in which case I will process the data accordingly.
As soon as there is data to be processed, the CPU usage gets low, way lower than if there was no data to process.
I know why my CPU usage is high : the loop will check as often as possible if there is something to read. On the plus side, there is close to no delay when recieving data, but no, that's not a viable solution.
Any ideas to change this ?
# UPDATE 1
As per Marc Gravell's idea, here is what I would like to understand and try :
byte buffer = new byte[4096];
while (_inputStream.CanRead
&& (readBytes = _inputStream.Read(buffer, 0, buffer.Length)) > 0
&& _state == STATE_CONNECTED)
{
for(int i = 0 ; i < readBytes; i++)
packet.Add(buffer[i]);
// or better: some kind of packet.AddRange(buffer, 0, readBytes)
}
How do you call this code snippet ?
Two questions :
If there is nothing to read, then the while condition will be
dismissed : what to do next ?
Once you're done reading, what do you do next ? What do you do to catch any new incoming packets ?
Here are some explanations that should help :
The android device is connected, via bluetooth, to another device that sends data. It will always send a pre-designed packet with a specified size (1024)
That device can stream the data continuously for some time but can also stop at any time for a long period too. How to deal with such behavior ?
An immediate fix would be:
don't read one byte at a time
don't create a new buffer per-byte
don't sit in a hot loop when there is no data available
For example:
byte buffer = new byte[4096];
while (_inputStream.CanRead
&& (readBytes = _inputStream.Read(buffer, 0, buffer.Length)) > 0
&& _state == STATE_CONNECTED)
{
for(int i = 0 ; i < readBytes; i++)
packet.Add(buffer[i]);
// or better: some kind of packet.AddRange(buffer, 0, readBytes)
}
Note that the use of readBytes in the original while check looked somewhat... confused; I've replaced it with a "while we don't get an EOF" check; feel free to add your own logic.
Is there any way to execute Binary file in an android application. without JNI wrapper approach.
plz give me sample codes.
try this
public void pump(InputStream in, OutputStream out, int size) {
byte[] buffer = new byte[4096]; // Or whatever constant you feel like using
int done = 0;
while (done < size) {
int read = in.read(buffer);
if (read == -1) {
throw new IOException("Something went horribly wrong");
}
out.write(buffer, 0, read);
done += read;
}
// Maybe put cleanup code in here if you like, e.g. in.close, out.flush, out.close
}
from this link Reading and writing binary file in Java (seeing half of the file being corrupted)