Run the projects in this order:
8761 - Eureka Server
8080 - Eureka Client
8081 - Eureka Feign
on Ubuntu you can open ports (This is more relevant if you are running on Docker) by running the following command:
$ ufw allow <Port>
For this example to work, you will need to know the Eureka IP address and port.
If you are running everything on localhost (without docker), all you need to do is run the Main classes on your favorite IDE) because localhost is set as the IP.
If you are running the images with docker, you will need to specify the IP address of the Eureka server in the application.properties file of the eureka-client and the eureka-server.
The property you should change in both projects is eureka.client.serviceUrl.defaultZone
If you run the images with docker and leave localhost as the Eureka IP address, it will look for the localhost of the docker image and therefore will not find the Eureka server.
To test, go to postman and do a get on http://localhost:8081/query Assuming that things are not running on Docker.