I'm setting up a kubernetes cluster, having one master node(a physical miniPC, running ubuntu server 18.04) and one slave-node(a laptop, running ubuntu 16.04).

Docker is the container I'm using in conjunction with kubernetes.

I run a demo application via

kubectl run hello-world --image=gcr.io/google-samples/hello-app:1.0  --port 8080

and expose it via

kubectl expose deployment hello-world --port=8080 --target-port=8080

The application starts on slave-node

alecu@slave-node:~$ sudo docker ps
CONTAINER ID        IMAGE                  COMMAND                  CREATED             STATUS              PORTS               NAMES
91967f160a7c        bc5c421ecd6c           "./hello-app"            About an hour ago   Up About an hour                        k8s_hello-world_hello-world-5bcc568dd9-xktwg_default_875609f4-90d0-11e9-9940-7cd30a0da72f_0

And I can access it from inside the container

alecu@slave-node:~$ sudo nsenter -t 21075 -n curl http://localhost:8080
Hello, world!
Version: 1.0.0
Hostname: hello-world-6899bf7846-t5pb7

But when I try to access it from outside the container I get connection refused:

alecu@slave-node:~$ curl http://localhost:8080
curl: (7) Failed to connect to localhost port 8080: Connection refused

netstat is not showing 8080 port

alecu@slave-node:~$ netstat -tnlp | grep 8080

curl is not working from master-node either

alecu@master-node:~$ kubectl describe service hello-world
Name:              hello-world
Namespace:         default
Labels:            <none>
Annotations:       <none>
Selector:          run=hello-world
Type:              ClusterIP
IP:                10.100.48.99
Port:              <unset>  8080/TCP
TargetPort:        8080/TCP
Endpoints:         192.168.1.18:8080
Session Affinity:  None
Events:            <none>

alecu@master-node:~$ curl -v http://192.168.1.18:8080
* Rebuilt URL to: http://192.168.1.18:8080/
*   Trying 192.168.1.18...
* TCP_NODELAY set
^C
alecu@master-node:~$ curl -v http://10.100.48.99:8080
* Rebuilt URL to: http://10.100.48.99:8080/
*   Trying 10.100.48.99...
* TCP_NODELAY set
^C
alecu@master-node:~$

I 'ctrl+c'ed the curl command as it was endlessly waiting.

I do not get it why on slave-node port 8080 is not opened.

[EDIT] I patched the service to use NodePort

 kubectl patch svc hello-world --type='json' -p '[{"op":"replace","path":"/spec/type","value":"NodePort"}]'

but the curl is not working either on http://nodeIP:nodePort

alecu@master-node:~$ kubectl describe svc hello-world
Name:                     hello-world
Namespace:                default
Labels:                   run=hello-world
Annotations:              <none>
Selector:                 run=hello-world
Type:                     NodePort
IP:                       10.100.171.36
Port:                     <unset>  8080/TCP
TargetPort:               8080/TCP
NodePort:                 <unset>  30988/TCP
Endpoints:                192.168.1.21:8080
Session Affinity:         None
External Traffic Policy:  Cluster
Events:                   <none>
alecu@master-node:~$ curl -v http://10.100.171.36:30988
* Rebuilt URL to: http://10.100.171.36:30988/
*   Trying 10.100.171.36...
* TCP_NODELAY set
^C