code: public void setHost(String host) throws IllegalStateException {
          if (host == null) {
              throw new IllegalArgumentException("host parameter is null");
          }
          assertNotOpen();
          hostName = host;
      }
docs: Sets the host to connect to.
  
  @param host the host to connect to. Parameter value must be non-null.
  @throws IllegalStateException if the connection is already open