Fell into infinite loop while receiving file using datainputstream and bufferedinputstream

Question

I am trying to build a server program that receives file from client using DataInputStream and BufferedInputStream.

Here's my code and it falls into infinite loop, I think it's because of not using available() but I am not really sure.

DataInputStream din = new DataInputStream(new BufferedInputStream(s.getInputStream()));
//s is socket that connects fine
fos = new FileOutputStream(directory+"/"+filename);

byte b[] = new byte[512]; 
int readByte = din.read(b);
while(readByte != 1){
    fos.write(b);
    readByte = din.read(b);
    //System.out.println("infinite loop...");
}

Can anyone tell me why it falls into infinite loop? if it is because of not using available , would you please tell me how to use it? I actually googled, but I was confused with the usage. Thank you very much

Answer 1

I think you want to do while(readByte != -1). See the documentation (-1 means there is nothing more to read).

Response to Comment

This works for me:

FileInputStream in = new FileInputStream(new File("C:\\Users\\Rachel\\Desktop\\Test.txt"));
DataInputStream din = new DataInputStream(new BufferedInputStream(in));
FileOutputStream fos = new FileOutputStream("C:\\Users\\Rachel\\Desktop\\MyOtherFile.txt");

byte b[] = new byte[512]; 
while(din.read(b) != -1){
    fos.write(b);
}

System.out.println("Got out");

Answer 2

As Rachel pointed out, the read method on DataInputStream returns the number of bytes successfully read in, or -1 if the end has been reached. The idiomatic way to loop until the end has been reached is while(readByte != -1) whereas you had 1 by mistake. If it is never the case that exactly 1 byte is read then this will be an infinite loop (readByte will never change from -1 once the end of the stream has been reached). If by chance there is an iteration where exactly 1 byte is read, this would have actually terminated early instead of going into an infinite loop.

Answer 3

Your question has already been answered but this code has another problem which is corrected below. The canonical stream copy loop looks like this:

while ((count = in.read(buffer)) > 0)
{
  out.write(buffer, 0, count);
}