connect() failed (111: Connection refused) while connecting to upstream in kubernet service - nginx

Question

enter code hereIn web browser get error "502 Bad Gateway Nginx".
And client get error [connect() failed (111: Connection refused) while connecting to upstream, client: 206.189.90.189, server: abc.xxx.xyz, request: "POST / HTTP/1.1", upstream: "http://10.245.21.96:244/", host: "188.166.204.10"].
enter code hereCan you tell me how to solve it. I spend 1 months but can't not fix it. :(((
enter code here1/my nginx config:
server {
listen 80 ;
listen [::]:80 ;
server_name abc.xxx.xyz;
sendfile off;
# Add stdout logging
error_log /dev/stdout info;
access_log /dev/stdout;
error_page 404 /404.html;
location / {
proxy_pass http://abc-service.default:244/;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header Host $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_read_timeout 300s;
proxy_connect_timeout 75s;
proxy_buffer_size 128k;
proxy_buffers 4 256k;
proxy_busy_buffers_size 256k;
}
}
2/My config abc-service:
Name: abc-service
Namespace: default
Labels: io.kompose.service=abc
Annotations:
Selector: io.kompose.service=abc
Type: ClusterIP
IP Family Policy: SingleStack
IP Families: IPv4
IP: 10.245.21.96
IPs: 10.245.21.96
Port: 244-tcp 244/TCP
TargetPort: 244/TCP
Endpoints: 10.244.0.211:244
Port: 18081-tcp 18081/TCP
TargetPort: 18081/TCP
Endpoints: 10.244.0.211:18081
Session Affinity: None