使用Jjsonrpc4j连接OVSDB报错

使用jsonrpc4j远程调用ovsdb，报错

                JsonRpcHttpClient jsonRpcHttpClient = new JsonRpcHttpClient(new URL("http://192.168.1.177:6632"));
        Map<String, String> headers = new HashMap<>();
        headers.put("Accept", "application/json");
        headers.put("Content-Type", "application/json");
        jsonRpcHttpClient.setHeaders(headers);
        String result = jsonRpcHttpClient.invoke("list_dbs", null, String.class);
        System.out.println(result);

求大神帮助解决，谢谢！

https://blog.csdn.net/hjcenry/article/details/52440925