What are the differences between the regular expression engines such as emacs and posix-egrep?

The command find uses Emacs Regular Expressions by default. This can be changed to options such as posix-egrep. What are the differences in each engine in addition to syntaxes? For example, do each differ in performance, simplicity? Should a particular engine be used for specific scenarios (above and beyond personal preferences)?

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Can’t connect to nginx server from public IP address

Hi I have a nginx server running on a linux machine. I can connect it to from localhost using curl -v http://localhost:8080 fine. But can’t connect it to using curl -v http://<machine-ip>:8080, or from browser in some other machine. The config file is server { listen 8080; listen [::]:8080; root /var/www/html; index index.html index.htm index.nginx-debian.html;…

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