Everything works well with my digitalocean droplet and I can access it with the ip and with ssh. But it doesn't work when I am connecting through a university captive portal.
It's likely that your university's network is blocking certain ports. I would recommend reaching out to your university's IT department as they will be better able to help you troubleshoot. It's not uncommon for a network to restrict traffic to ports 80 and 443 (http and https) and restrict either entirely or to some locations, access on other ports. If this proves to be the case you can set these services to run on any port you like by updating their configuration and restarting them.
Thank you for your message. I used a port redirection from 80 to 5984 (I host a couch database) and it seems to work so far.