kubernetes – Connect to gRPC service from k8s

I have a grpc service written in java deployed on kubernetes.

> kubectl get svc -n data                                         
NAME                      TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)             AGE
rds-grpc     ClusterIP   10.90.8.137    <none>        8088/TCP,6543/TCP   285d

I have port forwarded to this service to access it locally

> kubectl port-forward svc/rds-grpc -n data 6543:6543             
Forwarding from 127.0.0.1:6543 -> 6543
Forwarding from [::1]:6543 -> 6543

However when I try to call these gRPC APIs from Postman.
It gives me back this error

Status code: 1 CANCELLED

If I try bloomRPC then it gives me back

{
  "error": "2 UNKNOWN: Stream removed"
}

How can I correctly port forward and call the gRPC Api ?