Filipe Gonçalves Filipe Gonçalves - 1 year ago 102
Android Question

Sending multiple files - end of each file in the byte[] buffer

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 = != -1){
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;
System.out.println("send thread - already sent this ammount : "+total);


Answer Source

You are reading the socket until read() returns -1. This is the end-of-stream condition (EOS). EOS happens when the peer closes the connection. Not when it finishes writing one file.

You need to send the file size ahead of each file. You're already doing a similar thing with the file count. Then make sure you read exactly that many bytes for that file:

And This Is Sample Code

String filename = dis.readUTF();
long fileSize = dis.readLong();
FileOutputStream fos = new FileOutputStream(filename);
while (fileSize > 0 && (n =, 0, (int)Math.min(buf.length, fileSize)) != -1)
  fileSize -= n;

You can enclose all this in a loop that terminates when readUTF() throws EOFException. Conversely of course you have to call writeUTF(filename) and writeLong(filesize) at the sender, before sending the data.

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