Pod in ReplicaSet only 1 is ready

I'm using K3S (debian 10) and I'm super noob for kuber.

Here is the issue:

server:~# kubectl get pod 
NAME                  READY   STATUS    RESTARTS   AGE
vlmcsd-server-q4vfv   1/1     Running   0          15m
vlmcsd-server-b6qmk   0/1     Pending   0          3s
vlmcsd-server-tvsnr   0/1     Pending   0          3s
vlmcsd-server-lg6gw   0/1     Pending   0          3s

Here is the k8file:

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: vlmcsd-server
spec:
  replicas: 4
  selector:
    matchLabels:
      role: server

  template:
    metadata:
      labels:
        role: server
    spec:
      containers:
      - name: vlmcsd-1
        image: mikolatero/vlmcsd
        ports:
          - name: service-vlmcsd
            containerPort: 1688
            hostPort: 1688
            protocol: TCP  

So, Why only one pod is READY? As far as I can guess, port conflict? And is that mean ports name containerPort hostPort is direct port mapping rather SLB or something?

If it's port conflict, Which networking should I use?

server:~# kubectl describe pod/vlmcsd-server-q4vfv
Name:         vlmcsd-server-q4vfv
Namespace:    default
Priority:     0
Node:         tower.rczhiyun.local/10.188.180.251
Start Time:   Fri, 06 Aug 2021 14:50:44 +0800
Labels:       role=server
Annotations:  <none>
Status:       Running
IP:           10.42.0.21
IPs:
  IP:           10.42.0.21
Controlled By:  ReplicaSet/vlmcsd-server
Containers:
  vlmcsd-1:
    Container ID:   containerd://f45628cff396ae95a0678c4c5d8160ef83e068f5fbdf2b76f7528404644e588a
    Image:          mikolatero/vlmcsd
    Image ID:       docker.io/mikolatero/vlmcsd@sha256:d4eb626c762780fa37ecdb4e3efabb666b7dbf8355dfebc874e21ba780e3803c
    Port:           1688/TCP
    Host Port:      1688/TCP
    State:          Running
      Started:      Fri, 06 Aug 2021 14:50:47 +0800
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-n77c5 (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  kube-api-access-n77c5:
    Type:                    Projected (a volume that contains injected data from multiple sources)
    TokenExpirationSeconds:  3607
    ConfigMapName:           kube-root-ca.crt
    ConfigMapOptional:       <nil>
    DownwardAPI:             true
QoS Class:                   BestEffort
Node-Selectors:              <none>
Tolerations:                 node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                             node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
  Type     Reason            Age   From               Message
  ----     ------            ----  ----               -------
  Warning  FailedScheduling  21m   default-scheduler  0/1 nodes are available: 1 node(s) didn't have free ports for the requested pod ports.
  Warning  FailedScheduling  21m   default-scheduler  0/1 nodes are available: 1 node(s) didn't have free ports for the requested pod ports.
  Normal   Scheduled         21m   default-scheduler  Successfully assigned default/vlmcsd-server-q4vfv to tower.rczhiyun.local
  Normal   Pulling           21m   kubelet            Pulling image "mikolatero/vlmcsd"
  Normal   Pulled            21m   kubelet            Successfully pulled image "mikolatero/vlmcsd" in 2.377603969s
  Normal   Created           21m   kubelet            Created container vlmcsd-1
  Normal   Started           21m   kubelet            Started container vlmcsd-1

server:~# kubectl describe pod/vlmcsd-server-b6qmk
Name:           vlmcsd-server-b6qmk
Namespace:      default
Priority:       0
Node:           <none>
Labels:         role=server
Annotations:    <none>
Status:         Pending
IP:             
IPs:            <none>
Controlled By:  ReplicaSet/vlmcsd-server
Containers:
  vlmcsd-1:
    Image:        mikolatero/vlmcsd
    Port:         1688/TCP
    Host Port:    1688/TCP
    Environment:  <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-ztdjn (ro)
Conditions:
  Type           Status
  PodScheduled   False 
Volumes:
  kube-api-access-ztdjn:
    Type:                    Projected (a volume that contains injected data from multiple sources)
    TokenExpirationSeconds:  3607
    ConfigMapName:           kube-root-ca.crt
    ConfigMapOptional:       <nil>
    DownwardAPI:             true
QoS Class:                   BestEffort
Node-Selectors:              <none>
Tolerations:                 node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                             node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
  Type     Reason            Age    From               Message
  ----     ------            ----   ----               -------
  Warning  FailedScheduling  6m22s  default-scheduler  0/1 nodes are available: 1 node(s) didn't have free ports for the requested pod ports.
  Warning  FailedScheduling  6m20s  default-scheduler  0/1 nodes are available: 1 node(s) didn't have free ports for the requested pod ports.