Nginx configuration with proxy pass...

default.conf

server {
    listen       80;
    server_name  localhost;

    error_page 404 = @fallback;
    error_page 400 = @fallback;

    proxy_intercept_errors on;

    location / {
        proxy_pass http://localhost:8080;
    }

    location @fallback {
        proxy_pass http://localhost:8000;
    }
}