TCP and UDP services

The Kubernetes ingress resource only supports services over HTTP and HTTPS. Using NGINX Ingress Controller, however, you can receive external TCP/UDP traffic from non-HTTP protocols and route them to internal services using TCP/UDP port mappings.

Expose a TCP service

To expose TCP services, set the following parameters in the MKE 4 configuration file.

In the example procedure, a tcp-echo service that is running in the default namespace on port 9000 is exposed using the port 9000, on NodePort 33011.

1. Deploy a sample TCP service listening on port 9000, to echo back any text it receives with the prefix hello:

   cat <<EOF | kubectl apply -f -
   apiVersion: v1
   kind: Service
   metadata:
     name: tcp-echo
     labels:
       app: tcp-echo
       service: tcp-echo
   spec:
     selector:
       app: tcp-echo
     ports:
       - name: tcp
         port: 9000
   
   ---
   
   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: tcp-echo
   spec:
     replicas: 1
     selector:
       matchLabels:
         app: tcp-echo
     template:
       metadata:
         labels:
           app: tcp-echo
       spec:
         containers:
           - name: tcp-echo
             image: docker.io/istio/tcp-echo-server:1.2
             imagePullPolicy: IfNotPresent
             args: [ "9000", "hello" ]
             ports:
               - containerPort: 9000
   EOF

2. Verify that the deployment was created correctly:

   kubectl get deploy tcp-echo

   Example output:

   NAME           READY   UP-TO-DATE   AVAILABLE   AGE
   tcp-echo       1/1     1            1           39s

3. Verify that the service is running:

   kubectl get service tcp-echo

   Example output:

   NAME           TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)    AGE
   tcp-echo       ClusterIP   10.96.172.90   <none>        9000/TCP   46s

4. Configure Ingress Controller to expose the TCP service:

   1. Verify that the enabled parameter for the ingressController option in the MKE configuration file is set to true.

   2. Modify the MKE configuration file to expose the newly created TCP service:

      ingressController:
        enabled: true
        tcpServices:
          "9000": default/tcp-echo:9000
        nodePorts:
          tcp:
            9000: 33011

5. Apply the MKE configuration file:

   mkectl apply  -f mke.yaml

6. Test the TCP service by sending the text hello world:

   echo "world" | netcat <WORKER_NODE_IP> 33011
   hello world

   The service should respond with hello world.

7. Check the tcp-echo logs:

   1. Obtain the Pod name:

      kubectl get pods --selector=app=tcp-echo

      Example output:

      NAME                        READY   STATUS    RESTARTS   AGE
      tcp-echo-544849bd8f-6jscx   1/1     Running   0          45h

   2. Access the log:

      kubectl logs tcp-echo-544849bd8f-6jscx

      Example output:

      listening on [::]:9000, prefix: hello
      request: world
      response: hello world

8. Remove the Kubernetes resources, which are no longer needed:

   kubectl delete service tcp-echo
   kubectl delete deployment tcp-echo

Expose a UDP service

To expose UDP services, set the following parameters in the MKE 4 configuration file.

In the example procedure, a udp-listener service running in the default namespace on port 5005 is exposed using the port 5005, on NodePort 33012.

1. Deploy a sample UDP service listening on port 5005:

   cat <<EOF | kubectl apply -f -
   apiVersion: v1
   kind: ServiceAccount
   metadata:
     name: udp-listener
   
   ---
   
   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: udp-listener
     labels:
       app: udp-listener
   spec:
     replicas: 1
     selector:
       matchLabels:
         app: udp-listener
     template:
       metadata:
         labels:
           app: udp-listener
       spec:
         containers:
           - name: udp-listener
             image: mendhak/udp-listener
             ports:
               - containerPort: 5005
                 protocol: UDP
                 name: udp
   
   ---
   
   apiVersion: v1
   kind: Service
   metadata:
     name: udp-listener
   spec:
     ports:
       - port: 5005
         targetPort: 5005
         protocol: UDP
         name: udp
     selector:
       app: udp-listener
   EOF

2. Verify that the deployment was created correctly:

   kubectl get deploy udp-listener

   Example output:

   NAME           READY   UP-TO-DATE   AVAILABLE   AGE
   udp-listener   1/1     1            1           31s

3. Verify that the service is running:

   kubectl get service udp-listener

   Example output:

   NAME           TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)    AGE
   udp-listener   ClusterIP   10.96.19.229   <none>        5005/UDP   37s

4. Configure Ingress Controller to expose the UDP service:

   1. Verify that the enabled parameter for the ingressController option in the MKE configuration file is set to true.

   2. Modify the MKE configuration file to expose the newly created UDP service:

      ingressController:
        enabled: true
        udpServices:
          "5005": default/udp-listener:5005
        nodePorts:
          udp:
            5005: 33012

5. Apply the MKE configuration file:

   mkectl apply  -f mke.yaml

6. Test the UDP service by sending the UDP Datagram Message:

   echo "UDP Datagram Message" | netcat -v -u <WORKER_NODE_IP> 33012

7. Check the udp-listener logs:

   1. Obtain the Pod name:

      kubectl get pods --selector=app=udp-listener

      Example output:

      NAME                           READY   STATUS    RESTARTS   AGE
      udp-listener-f768d8db4-v69jr   1/1     Running   0          44h

   2. Access the log:

      kubectl logs udp-listener-f768d8db4-v69jr

      Example output:

      Listeningon UDP port 5005
      UDP Datagram Message

8. Remove the Kubernetes resources, which are no longer needed:

   kubectl delete service udp-listener
   kubectl delete deployment udp-listener