The connection was reset

[greagain]

I always get this error when try to connect the server:
The connection to the server was reset while the page was loading.

The site could be temporarily unavailable or too busy. Try again in a few moments.
If you are unable to load any pages, check your computer’s network connection.
If your computer or network is protected by a firewall or proxy, make sure that Firefox is permitted to access the web.

[mpulukkinen]

If you are using docker-compose up, the docker-compose.yml is not correctly configured, this worked for me (bolded the most important part):
version: '3'

services:
opus-mt:
build: .
volumes:
- somepathtomodels:/usr/src/app/models
ports:
- 8125:80
command: venv/bin/python3 server.py -c services.json -p 80
I used different port, because I had some weird issues with ports being reserved