Set<BigInteger> ids = new HashSet<BigInteger>();
for (int i = 0; i < CLIENT_COUNT; i++) {
// create the first session & login
WonderlandSession session = new WonderlandSessionImpl(serverInfo);
session.login(new LoginParameters(username, password.toCharArray()));
logger.info("Login with id " + session.getID());
assert session.getID() != null : "Session ID is null";
assert !ids.contains(session.getID()) : "Duplicate id " + session.getID();