How to enable outbound connections for a Docker container?

Question

I have an ASP.NET Core application that is hosted in the Docker cloud (cloud provider is Azure). The application uses Hangfire to run recurring jobs in the background, and one of the jobs needs to request data from an external REST API. I noticed that any attempt at outbound communication fails, and I would like to know, how I can enable it.

The deployment consists of some other containers, whereby linked containers (services) can communicate with no problem. There is no special network configuration; the default "bridge" mode is used. Do I need to configure something in the container´s image, or do I need to make changes to the network settings... I have no clue.

Answer 1

There is no special network configuration; the default "bridge" mode is used.

According to your description, it seems you are using a VM and run docker on it. If you want to access this docker from Internet, we should map docker port to local port, for example:

docker run -d -p 80:80 my_image service nginx start

After we map port 80 to this VM, we should add inbound rules to Azure network security group(NSG), we can follow this article to add it.

Also we should add port 80 to OS filewall inbound rules.

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Update:

Sorry for misunderstand.

Here is my test, I install docker on Azure VM(Ubuntu 16), then create a centos docker, like this:

root@jasonvms:~# docker run -i -t centos bash
Unable to find image 'centos:latest' locally
latest: Pulling from library/centos
d9aaf4d82f24: Pull complete 
Digest: sha256:4565fe2dd7f4770e825d4bd9c761a81b26e49cc9e3c9631c58cfc3188be9505a
Status: Downloaded newer image for centos:latest
[root@75f92bf5b499 /]# ping www.google.com
PING www.google.com (172.217.3.100) 56(84) bytes of data.
64 bytes from lga34s18-in-f4.1e100.net (172.217.3.100): icmp_seq=1 ttl=47 time=7.93 ms
64 bytes from lga34s18-in-f4.1e100.net (172.217.3.100): icmp_seq=2 ttl=47 time=8.13 ms
64 bytes from lga34s18-in-f4.1e100.net (172.217.3.100): icmp_seq=3 ttl=47 time=8.15 ms
^C
--- www.google.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2001ms
rtt min/avg/max/mdev = 7.939/8.076/8.153/0.121 ms
[root@75f92bf5b499 /]# ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=51 time=1.88 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=51 time=1.89 ms
64 bytes from 8.8.8.8: icmp_seq=3 ttl=51 time=1.86 ms
c64 bytes from 8.8.8.8: icmp_seq=4 ttl=51 time=1.87 ms
64 bytes from 8.8.8.8: icmp_seq=5 ttl=51 time=1.78 ms
64 bytes from 8.8.8.8: icmp_seq=6 ttl=51 time=1.87 ms
^C
--- 8.8.8.8 ping statistics ---
6 packets transmitted, 6 received, 0% packet loss, time 5009ms
rtt min/avg/max/mdev = 1.783/1.861/1.894/0.061 ms
[root@75f92bf5b499 /]# 

I find it can community with the internet, could you please show me more information about your issue?