Why is this ObjectInputStream constructor blocking?

The ObjectInputStream constructor is blocking even though I have already instantiated the corresponding ObjectOutputStream and called flush() to write the header.

Anyone have any idea why?

socket =new Socket(ipAddr, port);

socket.setSoTimeout(TIMEOUT);// timeout after 1 minute

output =new ObjectOutputStream(socket.getOutputStream());

output.flush();

input =new ObjectInputStream(socket.getInputStream());

[583 byte] By [dfasdfsdafsadfasdfa] at [2007-11-27 6:17:23]