可能的原因：

1、项目引用的ES版本和ES服务的版本不一样；

2、端口不正确，tcp访问端口是9300；

3、cluster.name不正确，可以通过访问http://localhost:9200/查看ES服务下的cluster.name;

4、ES服务没启动；

简单demo：

import java.net.InetAddress;
import java.net.UnknownHostException;
import org.elasticsearch.action.search.SearchRequestBuilder;
import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.client.transport.TransportClient;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.transport.InetSocketTransportAddress;
import org.elasticsearch.index.query.QueryBuilders;
import org.elasticsearch.search.fetch.subphase.highlight.HighlightBuilder;
import org.elasticsearch.transport.client.PreBuiltTransportClient;
 
public class ElasticDemo {
 
     //测试demo
        @SuppressWarnings({ "resource", "unchecked" })
        public static void main(String[] aa) throws UnknownHostException {
            TransportClient client = null;
            Settings esSettings = Settings.builder()
                    .put("cluster.name", "elasticsearch") //设置ES实例的名称
                    .build();
            client = new PreBuiltTransportClient(esSettings)
                    .addTransportAddress(new InetSocketTransportAddress(InetAddress.getByName("127.0.0.1"), 9300));
            System.out.println("ElasticsearchClient 连接成功");
             
//          BulkRequestBuilder bulkRequest = client.prepareBulk();
//          try {
//              bulkRequest.add(client.prepareIndex("ko", "test", "14")
//                      .setSource(jsonBuilder()
//                              .startObject()
//                              .field("tableId", "14")
//                              .field("title", "tetstcccfffffccccccccccc")
//                              .field("content", "ttttttttfffffffttttttttttt")
//                              .endObject()
//                      )
//              );
//          } catch (IOException e) {
//              e.printStackTrace();
//          }
//          BulkResponse bulkResponse = bulkRequest.get();
//          if (bulkResponse.hasFailures()) {
//              System.out.println("失败：" + bulkResponse.toString());
//          }
//          System.out.println("操作成功");
             
            HighlightBuilder highlightBuilder = new HighlightBuilder().field("title").requireFieldMatch(true);
            highlightBuilder.preTags("<span style=\"color:red\">");
            highlightBuilder.postTags("</span>");
            highlightBuilder.boundaryMaxScan(4);
             
            SearchRequestBuilder searchRequestBuilder = client.prepareSearch("ko"); //可以是多个index
            //searchRequestBuilder.setQuery(QueryBuilders.termQuery("title", "ffff"));  //精确查询
            searchRequestBuilder.setQuery(QueryBuilders.wildcardQuery("title", "*文 el*"));  //模糊查询
            searchRequestBuilder.setFrom(0);
            searchRequestBuilder.setSize(2);
            searchRequestBuilder.highlighter(highlightBuilder);
            SearchResponse response = searchRequestBuilder.get();
            System.out.println(response);
        }
         
}