我使用confluent platform 3.3作为kafka连接器，同时使用下面的命令启动连接器，

./bin/connect-standalone ./etc/schema-registry/connect-avro-standalone.properties ./etc/kafka-connect-jdbc/connect-jdbc-source.properties

获取以下错误

ERROR Server died unexpectedly:  (io.confluent.kafka.schemaregistry.rest.SchemaRegistryMain:52)
org.apache.kafka.common.errors.TimeoutException: Timeout expired while fetching topic metadata
[2017-10-30 13:49:56,178] ERROR Failed to send HTTP request to endpoint: http://localhost:8081/subjects/jdbc-source-accounts-value/versions 
(io.confluent.kafka.schemaregistry.client.rest.RestService:156)

zookeeper正在kafka客户机2181端口上运行，我试图通过下面的命令启动schema

./bin/schema-registry-start ./etc/schema-registry/schema-registry.properties &

但是它没有显示任何错误信息，但是端口8081没有打开。请帮我解决这个问题。