How to connect two docker containers through localhost?

Question

I have two services running in separate containers, one is grunt(application) and runs off port 9000 and the other is sails.js (server) which runs off port 1337. What I want to try to do is have the client app connect with the server through localhost:1337. Is this feasible? Thanks.

Answer 1

HOST

You won't be able to connect to the other container with localhost (as localhost is the current container) but you can connect via the container host (the host that is running your container). In your case you need boot2docker VM IP (echo $(boot2docker ip)). For this to work, you need to expose your port at the host level (which you are doing with -p 1337:1337).

LINK

Another solution that is most common and that I prefer when possible, is to link the containers.

You need to add the --name flag to the server docker run command: --name sails_server

You need to add the --link flag to the application docker run command: --link sails_server:sails_server

And inside your application, you will be able to access the server at sail_server:1337 You could also use environment variables to get the server IP. See documentation: https://docs.docker.com/userguide/dockerlinks/

BONUS: DOCKER-COMPOSE

Your run commands may start to be a bit long... in this case I like to use docker-compose that allows me to define my containers and their relationships (volumes, names, link, commands...) in one file.