expose local webserver behind dynamic IP - c

Question

I've a simple webserver bound on 0.0.0.0:3000 on my machine which works as intended on local networks. By local network I mean to say, if my mobile or any other device is on the same network, it can access local webserver by going to the IP assigned to my machine and adding port 3000 to it. Eg 192.168.1.4:3000.
Now I've to expose it to the internet but not through some sort of 3rd party application like ngrok, localtunnel or browserSync. I know that these applications work perfectly, but since I've my own pet project of controlling home appliances, I don't want to rely on availability of 3rd party services. So the current state is, I cannot control it through the internet. Keeping in mind I don't have a static IP otherwise this would've been easier.
I already have a vps and a domain name assigned to it. I can send my currently allocated ip address (since it is dynamic), by using getifaddrs, to my server and keep track of it. But how do I expose my local server to the internet through it? Those 3rd party applications assign some sort of subdomains to each exposed server, and I'll be able to assign subdomains too, but I'm still not getting any way to expose the local webserver. Any help would be appreciated, thankyou :)

Answer 1

Step one, you need to expose your webserver at your internet access router.
Typically this requires you to configure port forwarding for (in your case) port 3000.
With this done, any client could access your service via (current external dynamic ip):3000
Step two, you need to dynamically map a fixed DNS name to your current dynamic ip. There are of course third party services (such as DynDNS) that would help you map yourfavoritename.dyndns.org to that ever-changing ip address.
If you want to do the latter without 3rd party, you need to have some static (web) server somewhere and could proceed as follows:
Clients visit http://www.yourstaticserver.example/ and that server redirects them to (current dynamic ip):3000.
Of course, for this to happen, your static server needs to know the dynamic ip and needs no find out about changes to it.
To this end, you could have your internal server contact the static server on a regular interval (such as once a minute), say, have it access http://www.yourstaticserver.example/some-secret-special-page and the static server always stores the REMOTE_ADDR of such a request (preferably with some authorization!) for its future redirections.
Actually, there is a step zero before step one: Be aware that exposing your server to the Internet means that you expose your server to the Internet. So I hope you have invested enough thought into security.