Docker curl to other container in same host - docker

Question

I have 2 containers, first one running on port 80 and the other is running on port 8022, I try to make a curl request from the container that`s is running on port 8022 to the container on port 80 and i get a empty response.
For the container on port 8022 i run this command:
docker run -d -it --privileged -p 0.0.0.0:8022:80 -v ~/path/to/my/app:/var/www/app --network=bridge --memory 1073741824 my/app:latest
If a make a curl request to other host form example google, I get the response correctly.
Thanks for help
UPDATED
Ok I can solve this, creating a network and using this network in both containers, then I add to host file of the 8022 container the IP of the port 80 container.
Thanks for #zero298 for help!!

Answer 1

This is a very simple example of how to do inter-container communication over a user-defined, bridged network. Here are the 3 files that I have defined to make this possible:
~/Desktop/code/bootstrap.sh
This will kick off the demo by first creating a user defined, isolated network that your containers can talk over named example_nw. It then creates a new container, named "servertest", that will hold the server we will curl to. I'm using a node container because I'm just more familiar with it.
It will also create a volume that binds to your machines ~/Desktop/code/ directory which should contain all the code that we are using, including the node server.js script. The server listens on port 3000 and responds with: "Hello World`".
After creating the server, it kicks off another container, named "curler" that will install curl (debian doesn't come with it installed). After that, it curls to servertest:3000 and gets the correct reply because they are both connected to the same docker, user-defined, network: example_nw.
After completing, it cleans up by killing the server container and removing the example_nw network.
#!/usr/bin/env bash
# Create user-defined network
docker network create example_nw
# Create server to listen to pings on our network
docker run \
--rm \
-d \
-v ~/Desktop/code:/my/stuff \
--name servertest \
--expose 3000 \
--network example_nw \
node node /my/stuff/server
# Create a curler
docker run \
-it \
--rm \
-v ~/Desktop/code:/my/stuff \
--name pingtest \
--network example_nw debian \
/my/stuff/curler.sh
# Clean up
docker container stop servertest
docker network rm example_nw
~/Desktop/code/server.js
This is a really simple node.js script that will create a server that listens on port 3000.
/*jslint node:true, esversion:6*/
"use strict";
const http = require("http"),
port = 3000;
// Make a server
const server = http.createServer((req, res) => {
console.log("Got request");
res.end("Hello World!\n");
});
// Have the server listen
server.listen(port, (err) => {
if (err) {
return console.error(err);
}
console.log(`Listening on port: ${port}`);
});
~/Desktop/code/curler.sh
This just installs curl in the container and then curls to servertest:3000.
#!/usr/bin/env bash
apt update
apt install -y curl
curl servertest:3000
Running ~/Desktop/code/bootstrap.sh will demonstrate the communication.
I would recommend reading the Docker documentation: Work with network commands because it gives a lot of good examples and use cases.

Answer 2

This is an example to use the user-generated network
docker network create mynetwork
docker run --network=mynetwork -d -p 127.0.0.1:8022:80 --name mynginx nginx
docker run -it --network=mynetwork appropriate/curl http://mynginx
Otherwise you can use the older --link option
docker run -d -p 127.0.0.1:8022:80 --name mynginx nginx
docker run -it --link=nginx appropriate/curl http://mynginx

Answer 3

Your container is not listening on port 8022, you've pushed the port 8022 to forward to the container's port 80. From container to container, you connect to the container port, not the published port on the host. So remove 8022 from your curl command to go to the default port 80.
For container to container networking, you need the containers to be on a common docker network. And for docker's internal DNS, you need to be on a docker network other than the default bridge network named "bridge" (that "bridge" network has some historical properties that does not have DNS enabled). You can docker network create $network_name and then run your containers with the --net $network_name option to implement this.
You do not need to modify the host files or use the deprecated "link" functionality for container to container networking.