Java sockets, everything written stays in memory

Question

I am sending images through sockets using ByteArrayOutputStreams like this.

ImageIO.write(image, "gif", byteArrayO);
       byte [] byteArray = byteArrayO.toByteArray();
       Connection.pw.println("" + byteArray.length);
       int old = Connection.client.getSendBufferSize();
       Connection.client.setSendBufferSize(byteArray.length);
       Connection.client.getOutputStream().write(byteArray, 0, byteArray.length);

Everything works OK, the image is like 130kb in the end, and I receive it like this

int nbrToRead = Integer.parseInt(slave.input.readLine().trim());
            int old = slave.socket.getReceiveBufferSize();
            slave.socket.setReceiveBufferSize(nbrToRead);
            byte[] byteArray = new byte[nbrToRead];
            int nbrRd = 0;
            int nbrLeftToRead = nbrToRead;
            while (nbrLeftToRead > 0) {
                int rd = slave.socket.getInputStream().read(byteArray, nbrRd, nbrLeftToRead);
                if (rd < 0)
                    break;
                nbrRd += rd; 
                nbrLeftToRead -= rd;
            }

            ByteArrayInputStream byteArrayI = new ByteArrayInputStream(byteArray);

            BufferedImage img = ImageIO.read(byteArrayI);

It works well, but every image sent the memory heap of java increases like 50 mb. I have tried setting the receivebuffersize, but it still stays up. It goes to maximum in heap, then stays for a while then stops.

How can I clear the buffer so when it has received the bytes it will dispose of them?

Answer 1

A couple of things spring to mind:

• You may be holding on to a reference to an object and it's not cleaned up by garbage collection. If the class that is doing the work is a singleton, this is a very common problem.
• Make sure you call close() on any IO classes that you are using (like the BufferedInputSteam).