Server throwing OutOfMemory Exception when reading byte array from TCP connection

Question

I'm still working on my push server! I have successfully implemented encryption using javax.crypto.cipher. This requires I read/write bytes to the socket's stream. I can send and receive just fine. Encryption works. But when there's nothing going over the air, the server throws an OutOfMemoryException. The readBytes function is:

public static byte[] readBytes() throws IOException {
    int len = dis.readInt();
    byte[] data = new byte[len];
    if (len > 0) {
        dis.readFully(data);
    }
    return data;
}

The code that calls this is:

 public String read() {
            byte[] encrypted,decrypted = null;
            try {
                    encrypted = readBytes();
                    if (encrypted.equals(new Byte[] {0})) return "";
                    if (encrypted.equals(null)) return null;
                    cipher.init(Cipher.DECRYPT_MODE, key);
                    decrypted = cipher.doFinal(encrypted);
            } catch (Exception e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
            }
            String afterEncryption = new String(decrypted);
            return afterEncryption;
    }

And read() is called in a while-loop:

while (true&loggedin&((inputLine=read())!=null)) {

And the exception that is thrown is:

Exception in thread "ServerThread" java.lang.OutOfMemoryError: Java heap space
    at ServerThread.readBytes(ServerThread.java:277)
    at ServerThread.read(ServerThread.java:245)
    at ServerThread.run(ServerThread.java:108)

Line 277 being the one that declares the byte array. The function that sends the byte array is:

    public static void sendBytes(byte[] myByteArray, int start, int len) throws IOException {
    if (len < 0)
        throw new IllegalArgumentException("Negative length not allowed");
    if (start < 0 || start >= myByteArray.length)
        throw new IndexOutOfBoundsException("Out of bounds: " + start);
    if (len > 0) {
        dos.writeInt(len);
        dos.write(myByteArray, start, len);
    }
}

sendBytes is only run when read() stops blocking. That's how the loop is designed to work.

If this code looks familiar, its because I found it on stack overflow!

The handshake works flawlessly, but as soon as it stops sending things, I get the exception about five seconds later.

Thank you for any help you can give me.

Answer 1

You are almost certainly getting out of sync in your protocol and reading data as though it was a length word. Trace your length words and byte array lengths as you send them and receive them and match them up.

You should really look into using CipherInputStream and CipherOutputStream for this: they do a lot of this grunt work for you. Or even SSL.