code: public static int findAvailablePortFrom(int minPort) {
  		for (int port = minPort; port < PORT_RANGE_MAX; port++) {
  			if (isPortAvailable(port)) {
  				return port;
  			}
  		}
  
  		throw new IllegalStateException(
  				String.format("Could not find an available tcp port in the range [%d, %d]", minPort, PORT_RANGE_MAX));
  	}
docs: 从某个端口开始，递增直到65535，找一个空闲端口.
  
  @throws IllegalStateException 范围内如无空闲端口，抛出此异常