public TestClient(String user) {
	try {
	    addr = InetAddress.getByName("localhost");
	} catch(java.net.UnknownHostException e) {
	    throw(new RuntimeException("localhost not known"));
	}
	this.user = user;
	this.cookie = new byte[64];
	tg = new ThreadGroup(HackThread.tg(), "Test client") {
		public void uncaughtException(Thread t, Throwable e) {
		    synchronized(errsync) {
			System.err.println("Exception in test client: " + TestClient.this.user);
			e.printStackTrace(System.err);
		    }
		    TestClient.this.stop();
		}
	    };
    }