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("");	        highlightBuilder.postTags("");	        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);	    }		}