java.net.BindException：从dashboard中的客户端获取度量时，无法分配请求

最近公司准备用Sentinel做限流降级，我本地引入搭建好环境，采用注解@SentinelResource的方式，wiki 中提到的jar 包都引用了，控制台显示正常。

使用压测工具进行压测时，控制台报错如下：

2019-04-12 15:44:08.983 ERROR 2152 --- [pool-2-thread-1] c.a.c.s.dashboard.metric.MetricFetcher : fetch metric http://172.30.4.87:8720/metric?startTime=1555055040000&endTime=1555055046000&refetch=false error

java.net.BindException: Can't assign requested address at sun.nio.ch.Net.connect0(Native Method) ~[na:1.8.0_191] at sun.nio.ch.Net.connect(Net.java:454) ~[na:1.8.0_191] at sun.nio.ch.Net.connect(Net.java:446) ~[na:1.8.0_191] at sun.nio.ch.SocketChannelImpl.connect(SocketChannelImpl.java:648) ~[na:1.8.0_191] at org.apache.http.impl.nio.reactor.DefaultConnectingIOReactor.processSessionRequests(DefaultConnectingIOReactor.java:273) [httpcore-nio-4.4.6.jar:4.4.6] at org.apache.http.impl.nio.reactor.DefaultConnectingIOReactor.processEvents(DefaultConnectingIOReactor.java:139) [httpcore-nio-4.4.6.jar:4.4.6] at org.apache.http.impl.nio.reactor.AbstractMultiworkerIOReactor.execute(AbstractMultiworkerIOReactor.java:348) [httpcore-nio-4.4.6.jar:4.4.6] at org.apache.http.impl.nio.conn.PoolingNHttpClientConnectionManager.execute(PoolingNHttpClientConnectionManager.java:194) [httpasyncclient-4.1.3.jar:4.1.3] at org.apache.http.impl.nio.client.CloseableHttpAsyncClientBase$1.run(CloseableHttpAsyncClientBase.java:64) [httpasyncclient-4.1.3.jar:4.1.3] at java.lang.Thread.run(Thread.java:748) [na:1.8.0_191]

环境： mac os jdk 1.8 使用工具 idea web 项目使用spring boot

请问是什么原因？

原提问者GitHub用户Force-King