Grpc.Core.RpcException: Status(StatusCode=Unavailable, Detail="Connection reset by peer")
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Grpc.Core.Internal.AsyncCall`2.UnaryCall(TRequest msg)
   at Grpc.Core.DefaultCallInvoker.BlockingUnaryCall[TRequest,TResponse](Method`2 method, String host, CallOptions options, TRequest request)
   at Grpc.Core.Interceptors.InterceptingCallInvoker.<BlockingUnaryCall>b__3_0[TRequest,TResponse](TRequest req, ClientInterceptorContext`2 ctx)
   at Grpc.Core.ClientBase.ClientBaseConfiguration.ClientBaseConfigurationInterceptor.BlockingUnaryCall[TRequest,TResponse](TRequest request, ClientInterceptorContext`2 context, BlockingUnaryCallContinuation`2 continuation)

  private readonly Polly.Retry.RetryPolicy RetryPolicy = Policy
           .Handle<RpcException>(t => t.Status.StatusCode == StatusCode.Unavailable)
           .Retry(1);

var server = new Server(new List<ChannelOption>
{
  new ChannelOption("grpc.keepalive_time_ms", 800000), // 發送 keepalive 探測消息的頻度
  new ChannelOption("grpc.keepalive_timeout_ms", 5000), // keepalive 探測應答超時時間
  new ChannelOption("grpc.keepalive_permit_without_calls", 1) // 是否允許在沒有任何調用時發送 keepalive
})
{
  Services = { ServiceA },
  Ports = { new ServerPort(host, port, ServerCredentials.Insecure) },
};

 var channelOptions = new List<ChannelOption>();

 // add max message length option 設最大接收數量
 channelOptions.Add(new ChannelOption(ChannelOptions.MaxReceiveMessageLength, (4 * 1024 * 1024) * 7))