Docker container cannot connect to host machine: No route to host

Question

I've been trying to setup a docker environment using docker compose. One issue that has me stumped is that my docker containers cannot reach my host machine.

I setup a container using the following compose file:

version: '3'
services:
  webapp:
    image: ...
    ports:
      - "8080:8080"

When I enter the container, I am able to ping my host machine:

ping ${dockerHostIP}

However when I try and retrieve the home page using curl inside the container:

curl http://${dockerHostIP}:8080

I get:

curl: (7) Failed connect to ${dockerHostIP}:8080; No route to host

I cannot figure out what should be done to resolve this No route to host error. Unfortunately I need to be able to do this as the web application makes requests using its hostname internally.

Traceroute Results:

traceroute ${dockerHostIP}
traceroute to ${dockerHostIP} (${dockerHostIP}), 30 hops max, 60 byte packets
 1  ${dockerHostName} (${dockerHostIP})  0.039 ms !X  0.012 ms !X  0.007 ms !X

Solution

To my surprise, it was actually a firewall issue in my case.

Update/Enable the tcp port [2375] on the docker host machine fixes the issue.

sudo firewall-cmd --zone=public --add-port=2375/tcp --permanent

sudo firewall-cmd --reload 

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