code: public static int getNextAvailablePort(int fromPort, int toPort) {
          if (fromPort < MIN_PORT_NUMBER || toPort > MAX_PORT_NUMBER || fromPort > toPort) {
              throw new IllegalArgumentException(format("Invalid port range: %d ~ %d", fromPort, toPort));
          }
  
          int nextPort = fromPort;
          //noinspection StatementWithEmptyBody
          while (!isPortAvailable(nextPort++)) { /* Empty */ }
          return nextPort;
      }
docs: Returns a currently available port number in the specified range.
  @param fromPort the lower port limit
  @param toPort the upper port limit
  @throws IllegalArgumentException if port range is not between {@link #MIN_PORT_NUMBER}
  and {@link #MAX_PORT_NUMBER} or <code>fromPort</code> if greater than <code>toPort</code>.
  @return an available port