怎么让域名后面不加端口号

server {
    listen 80;
    server_name example.com;

    location / {
        proxy_pass http://localhost:3000;
    }
}

server {
    listen 443 ssl;
    server_name example.com;

    ssl_certificate /path/to/certificate.crt;
    ssl_certificate_key /path/to/private.key;

    location / {
        proxy_pass http://localhost:3000;
    }
}

server {
    listen 80;
    server_name example.com;

    location / {
        proxy_pass http://localhost:3000;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }
}

netstat -tuln | grep 80

sudo ufw allow 80/tcp
sudo ufs allow 443/tcp

ssl_certificate /path/to/certificate.crt;
ssl_certificate_key /path/to/private.key;