code: public static AltsProtocolNegotiator createServerNegotiator(
        final TsiHandshakerFactory handshakerFactory, final LazyChannel lazyHandshakerChannel) {
      final class ServerAltsProtocolNegotiator extends AltsProtocolNegotiator {
  
        @Override
        public ChannelHandler newHandler(GrpcHttp2ConnectionHandler grpcHandler) {
          TsiHandshaker handshaker = handshakerFactory.newHandshaker(/*authority=*/ null);
          return new BufferUntilAltsNegotiatedHandler(
              grpcHandler,
              new TsiHandshakeHandler(new NettyTsiHandshaker(handshaker)),
              new TsiFrameHandler());
        }
  
        @Override
        public void close() {
          logger.finest("ALTS Server ProtocolNegotiator Closed");
          lazyHandshakerChannel.close();
        }
      }
  
      return new ServerAltsProtocolNegotiator();
    }
docs: Creates a negotiator used for ALTS server.