Java StreamCorruptedException at Socket Connection

Question

I want to send some Object with sockets, but this doesn't work always. Sometimes it works, sometimes not. And then I get a StreamCorruptedException. Why do I get it? Here my client:

DataOutputStream os = new DataOutputStream(socket.getOutputStream());
os.writeUTF(output);
os.flush();
ObjectInputStream in = new ObjectInputStream(socket.getInputStream());
Post[] returnArray;
while ((returnArray = (Post[]) in.readObject()) != null) {
       return returnArray;
 }

I get the error here: ObjectInputStream in = new ObjectInputStream(socket.getInputStream());

And at the server I have this:

public void returnObjectPosts(Post[] sendPosts){
    try{
        ObjectOutputStream os = new ObjectOutputStream(client.getOutputStream());
        os.writeObject(sendPosts);
        os.flush();
        os.close();
    }catch(UnknownHostException e){
        e.printStackTrace();
    }catch(IOException e){
        e.printStackTrace();
    }
}