dubbo直接代码下使用multicast组播注册中心报错:No provider available for the service

服务端代码:

public class DubboMulticastServer {
    public static void main(String[] args) throws IOException {
        //应用配置
        ApplicationConfig applicationConfig = new ApplicationConfig();
        applicationConfig.setName("user-server");
 
        //配置中心
        RegistryConfig registryConfig = new RegistryConfig();
        registryConfig.setProtocol("multicast");
        registryConfig.setAddress("224.5.6.7:1234");
        //端口
        ProtocolConfig protocolConfig = new ProtocolConfig();
        protocolConfig.setName("dubbo");
        protocolConfig.setPort(-1);
 
        ServiceConfig serviceConfig = new ServiceConfig();
        serviceConfig.setApplication(applicationConfig);
        serviceConfig.setRegistry(registryConfig);
        serviceConfig.setProtocol(protocolConfig);
        serviceConfig.setInterface(UserService.class);
        //serviceConfig.setInterface("com.test.client.Us