The stream has a reference graph, so an object which is sent twice will not give two objects on the other end, you will only get one. And sending the same object twice separately will give you the same instance twice (each with the same data – which is what you’re seeing). See the reset() … Read more
This problem can happen if you construct a new ObjectInputStream or ObjectOutputStream over the same socket instead of using the same ones for the life of the socket; use another kind of stream over the same socket as well; or, use the object streams to read or write something that isn’t an object and you … Read more
Here’s the trick: subclass ObjectOutputStream and override the writeStreamHeader method: public class AppendingObjectOutputStream extends ObjectOutputStream { public AppendingObjectOutputStream(OutputStream out) throws IOException { super(out); } @Override protected void writeStreamHeader() throws IOException { // do not write a header, but reset: // this line added after another question // showed a problem with the original reset(); } … Read more