docs: public final void addServer(final String server, final int port, int weight) throws IOException {
      if (weight <= 0) {
        throw new IllegalArgumentException("weight<=0");
      }
      this.checkServerPort(server, port);
      this.connect(new InetSocketAddressWrapper(this.newSocketAddress(server, port),
          this.serverOrderCount.incrementAndGet(), weight, null));
    }