Connecting Docker Containers

Hello Helpful Developers,

I'm having issues connecting docker containers. I have built a subversion docker container and a mongo docker container.

docker run -d -p 3343:3343 -p 4434:4434 -p 18080:18080 --name svn-server mamohr/subversion-edge

docker run -p 27017:27017 --name my-mongo -d mongo

I'm able to hit http://x.x.x.x:18080/ from a browser, but unable to curl from the my-mongo instance. I can talk to each container from my development machine, but unable to talk from container to container.

I see things like --net=bridge, host, ????, but I'm getting confused.

Please help.....

Borrowing this schema from SDN hub, imagine that C1 is your SVN container and C2 is your Mongo container:

Both containers are connected to docker0 bridge and NATed to external 192.168.50.16 network.

To connect from your Mongo container, check the bridge0 IP address of the SVN container:

# docker inspect <svn-container-name>

        "Networks": {
            "bridge0": {
                "IPAddress": "172.17.0.19",
            }

then CURL directly to it's bridge0 IP address:

curl http://172.17.0.19:18080/

docker network connect, When connecting to an existing network using docker network connect , you can use the --alias flag to specify an additional network alias for the container on that � Method 2: Docker Network Connect Containers ( Recommended ) This is a recommended and widely accepted method to connect two containers together, this exactly does the same thing as Docker Link which is connecting the containers to the same network. While Docker Link is doing the task in an abstracted manner Docker Network is doing the same in a

To get you immediately going, you can start your hosts with --net=host and then both containers and host will be able to communicate. Or you can use link( --link ) between from mongo to the other container.

There is lot to explain about docker networking and the docker documentation will be good point to start.

Read the documentation at https://docs.docker.com/engine/userguide/networking/dockernetworks/

Networking with standalone containers, Why connect containers. You should be running a single process per docker container, this means your application code (say nodejs) and your� A container is launched and set. Connecting Containers To connect our container with another container we can set this up using docker-compose, the fun part is we can run multiple containers and decentralized parts of the same application.

I would advice you to take a look at docker compose. I think it's the best way to manage a system, which is composed of many containers.

Here is the official guide: https://docs.docker.com/compose/

Container networking, Connecting to a running Docker container is helpful when you want to see what is happening inside the container. In this tutorial, we will� Docker containers are in a way like lightweight virtual machines. They are completely isolated from each other, and from the host. By default, Docker will create a bridge network. This default network doesn’t allow the containers to connect to the host. So, we’ll need to make some additional configurations.

Docker containers by default start attached to a bridge network called default. You can do docker network ls and see the networks you have available. You can also create networks with different attributes etc...

So in your case, both your containers are being started on the same default network, which means they should be able to communicate with each other just fine. In fact, if you only want your SVN server to be able to talk to Mongo (and don't need to connect to mongo from your host) you don't even need to expose ports on the Mongo container. Containers on the same network as each can communicate with each other just fine without ports being exposed. Exposing ports is to allow host > container connectivity.

So, what hostname / port are you using when you try to curl from the mongo instance to your SVN instance? You should be using svn-server as that will resolve to the SVN container (using Docker's built-in DNS resolution).

Connecting docker containers, Connecting docker containers for decentralized architecture. Tagged with docker, networking, node. You can connect your Docker host to a container with a unique hostname, or directly link two containers. Using Docker Compose can simplify this process even further by allowing you to declare connections in the docker-compose.yml file so that they are automatically established when the containers are brought up.

Direct container to container networking via container name can be achieved with a user defined network.

docker network create mynet
docker run -d --net=mynet --name svn-server mamohr/subversion-edge
docker run -d --net=mynet --name my-mongo mongo

docker exec <svn-id> ping my-mongo
docker exec <mongo-id> ping svn-server

You should always be able to connect to mapped ports though, even in your current setup. The hosts runs a process that listens on that port so any host IP should do.

$ docker run -d -p 8080:80 --net=mynet --name sleep busybox nc -lp 80 -e echo here!
63115ef88664f1186ea012e41138747725790383c741c12ca8675c3058383e68
$ ss -lntp | grep 8080
LISTEN     0      128                      :::8080                    :::*      users:(("exe",pid=6287,fd=4))
$ docker run busybox nc <any_host_ip> 8080
here!

How to Connect to a Docker Container, Using --link was the only way of connecting containers before the advent of docker networks. These provide a "cleaner" solution to the problem� Connecting docker containers. Twice recently I have seen people ask on twitter about how to link docker containers. In both instances they were given overly-complex answers that are out of date with the current state of docker. So today I will show you how to do it correctly for docker v1.10.0+ Why connect containers

Docker Basics- How to connect containers using docker networks , In this docker container linking tutorial you will learn how to link docker containers, the Duration: 9:17 Posted: Mar 1, 2019 Managing SQL Server Docker containers in macOS; Connecting to a SQL Server Docker Container Running in macOS; In the second part of this article series, you learned about the container’s nature (ephemeral) and a few details about its life cycle.

Connecting two docker containers, There is a docker exec command that can be used to connect to a container that is already running. Use docker ps to get the name of the existing container; Use� Using --link was the only way of connecting containers before the advent of docker networks. These provide a "cleaner" solution to the problem of inter-container communication and at the same time solves 2 of the major limits of links: restart of linked container breaks the link; links are not supported between containers running on different hosts

How to Link Docker Containers, Virtual network attach for Docker containers in Azure: The plug-in can be used in cases where you don’t want to create a Kubernetes cluster, and would like to create Docker containers with virtual network attach, in virtual machines. For detailed instructions, see Deploy the plug-in for Docker. Next steps

Comments
  • The container names can be used to resolve the IP if you use a user defined bridge rather than docker0.
  • --net=host should be used with caution, and is not the right answer here.
  • Yes, On production --net=host is not ideal. But on a development machine, where there can be dependent services which are not dockerized and may need direct access for running the app, IMO its okay. ex: running local instance of a DB
  • I'm trying to curl dockerHost:18080 from the mongo container which is getting a not able to connect to host. So should I just to curl svn-server:18080