Solution for multiple Docker containers not having the same port number

version: '2'
networks:
 nn:
  driver: bridge
services:
 service-1:
  container_name: service-1
  image: foo
  networks:
   -nn
  volumes:
   - ./logs/1:/apps/aaa/bbb-logs
   - ./common:/apps/aaa/bbb
   - ./xxx/1.xml:/ccc/targets.xml
  entrypoint: foo.sh
  command: start app=foo port=6000
  
 service-2:
  container_name: service-2
  image: foo
  networks:
   -nn
  volumes:
   - ./logs/2:/apps/aaa/bbb-logs
   - ./common:/apps/aaa/bbb
   - ./xxx/2.xml:/ccc/targets.xml
  entrypoint: foo.sh
  command: start app=foo port=6000
 
 service-3:
  container_name: service-3
  image: foo
  networks:
   -nn
  volumes:
   - ./logs/3:/apps/aaa/bbb-logs
   - ./common:/apps/aaa/bbb
   - ./xxx/3.xml:/ccc/targets.xml
  entrypoint: foo.sh
  command: start app=foo port=6000
 
 service-4:
  container_name: service-4
  image: foo
  networks:
   -nn
  volumes:
   - ./logs/4:/apps/aaa/bbb-logs
   - ./common:/apps/aaa/bbb
   - ./xxx/4.xml:/ccc/targets.xml
  entrypoint: foo.sh
  command: start app=foo port=6000  
 
 nginx:
  container_name: nginx
  image: nginx:1.15-alpine
  ports:
   - 6001:6001
  networks:
   -nn
  volumes:
   - ./nginx/nginx.conf:/etc/nginx/nginx.conf
   - ./logs/nginx:/var/log/nginx

worker_processes 8;
worker_rlimit_nofile 65535; 
events {
    use epoll;
    worker_connections 65535;
 }
 
http {
    include mime.types;
    default_type aplication/octet-stream;
    sendfile on;
    log_format main '[$time_local]$remote_addr-$upstream_addr "$request" $status $body_bytes_sent';
 
    upstream service1.local {
      server service-1:6000;
    }
    upstream service2.local {
     server service-2:6000;
    }
    upstream service3.local {
      server service-3:6000;
    }
    upstream service4.local {
      server service-4:6000;
    }
 
    server {
      listen 6001;
      client_max_body_size 100M;
      proxy_set_header Host $host:$server_port;
      proxy_set_header X-Real-IP $remote_addr;
      proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
 
      location /service1/ {
        proxy_pass http://service1.local/;
      }
      location /service2/ {
        proxy_pass http://service2.local/;
      }
      location /service3/ {
        proxy_pass http://service3.local/;
      }
      location /service4/ {
        proxy_pass http://service4.local/;
      }
      location /nginx_status {
        stub_status on;
        access_log off;
      }
    }
}