Nginx is a network tool with web server capabilities. It can also do pretty much everything you want as long as it's ipv4 or ipv6 over TCP, UDP or HTTP as it, and specifically the openresty distribution are highly scriptable. For example, a recent use case I solved with it was using it as a DNS (53 and DoT) proxy which also provided DoH and filtering.

For more use cases look at Kong, which is almost completely built on openresty.