Cannot connect to the Docker daemon at tcp://docker.example.com:2376. Is the docker daemon running?

[kariae]

I run the image through docker-compose everything from the logs looks fine but when I try to connect to the Docker daemon from my local computer I have this error, I checked the port with nmap and it's open

I have swarm and traefik running on the server, so I tried to deploy the image on swarm and expose the port using traefik, I had the same issue

Any idea where I can debug this, please?

[kekru]

You could try if you can connect with curl. Maybe then you find the problem.
For me this works:

# Checkout this git repo
$ docker-compose up -d
$ curl -v --cacert certs/client/ca.pem --cert certs/client/cert.pem --key certs/client/key.pem https://abc.127.0.0.1.nip.io:8443/containers/json

* Uses proxy env variable no_proxy == '192.168.99.100'
*   Trying 127.0.0.1:8443...
* Connected to abc.127.0.0.1.nip.io (127.0.0.1) port 8443 (#0)
* ALPN, offering h2
* ALPN, offering http/1.1
* successfully set certificate verify locations:
*   CAfile: certs/client/ca.pem
  CApath: none
* TLSv1.3 (OUT), TLS handshake, Client hello (1):
* TLSv1.3 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS handshake, Certificate (11):
* TLSv1.2 (IN), TLS handshake, Server key exchange (12):
* TLSv1.2 (IN), TLS handshake, Request CERT (13):
* TLSv1.2 (IN), TLS handshake, Server finished (14):
* TLSv1.2 (OUT), TLS handshake, Certificate (11):
* TLSv1.2 (OUT), TLS handshake, Client key exchange (16):
* TLSv1.2 (OUT), TLS handshake, CERT verify (15):
* TLSv1.2 (OUT), TLS change cipher, Change cipher spec (1):
* TLSv1.2 (OUT), TLS handshake, Finished (20):
* TLSv1.2 (IN), TLS handshake, Finished (20):
* SSL connection using TLSv1.2 / ECDHE-RSA-AES256-GCM-SHA384
* ALPN, server did not agree to a protocol
* Server certificate:
*  subject: CN=abc.127.0.0.1.nip.io
*  start date: Oct 10 22:14:39 2020 GMT
*  expire date: Oct 10 22:14:39 2021 GMT
*  subjectAltName: host "abc.127.0.0.1.nip.io" matched cert's "abc.127.0.0.1.nip.io"
*  issuer: C=GB; ST=London; L=London; O=ExampleCompany; OU=IT; CN=example.com; emailAddress=test@example.com
*  SSL certificate verify ok.
> GET /containers/json HTTP/1.1
> Host: abc.127.0.0.1.nip.io:8443
> User-Agent: curl/7.71.1
> Accept: */*
>
* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< Api-Version: 1.40
< Content-Type: application/json
< Date: Mon, 26 Oct 2020 19:02:42 GMT
< Docker-Experimental: false
< Ostype: linux
< Server: Docker/19.03.13 (linux)
< Transfer-Encoding: chunked
<
[{"Id":"3c465cf46f5d6f9575befe1cb515deaded55fed366f1d8e7df12da2cc2218313","Names":["/docker-remote-api-tls_remote-api_1"],"Image":"docker-remote-api-tls_remote-api","ImageID":"sha256:bc402743710f62d52a4f8ed69cb2f60aea76c3463c71cd9355be1ea7f773f733","Command":"/docker-entrypoint.sh nginx -g 'daemon off;'","Created":1602600275,"Ports":[{"IP":"0.0.0.0","PrivatePort":443,"PublicPort":8443,"Type":"tcp"},
...
* Connection #0 to host abc.127.0.0.1.nip.io left intact