I understand your points.
Sure not a bad thing for the community to have a wrapper of emqtt.
Still I’d rather use emqtt directly before pulling in a dependency.
The code I posted is just the first step, but it will surely be way less than 500loc.
It’s not directly used in :gen_udp.connect options (see: emqtt_sock.erl) but you can try to override the default configuration:
(never done this)
The next step will be to try to get this working in Github CI. This is going to be a bit useless if it breaks all my CI tests 
On the topic of IPv6, looks like I need to set:
tcp_opts: [
:inet6
],
Which is one of the opts supported by emqtt. It annoys me that this isn’t the default in erlang - it should be the default to try IPv6 then IPv4 - but I guess we are stuck with legacy code and the need to provide a stable API.
I might as well describe my TLS solution. I need to set:
ssl_opts: [
server_name_indication: 'hostname.example.org',
verify: :verify_peer,
cacertfile: mqtt_ca_cert_file
],
If I don’t set the server_name_indication to the hostname (must be a charlist!), the hostname verification of the certificate fails. The documentation seems to indicate that this should default to the hostname supplied to the connect call - ssl — OTP 29.0.2 (ssl 11.7.2) - which I thought meant it should be OK if I don’t supply it. But after using the debugger on the code (and only vaguely understanding it) I strongly suspect the supplied hostname is the IP address, which - as per the documentation (and common sense!) won’t work.
Oh there is definitely demand for an elixir MQTT client.
I tried several days to get a solution that connects to AWS IOT.
I tried tortoise and the erlang one.
The problem was always SSL on the beam. Never managed to get it working.
But this was in OTP 20 and there were some problems in SSL/crypto around that release I think.
Any ideas of the build failures? What seems weird is that it starts off compiling files fine. Then it gets to a point where it won’t compile the file even when repeatedly re-tried.
Tried a number of things, all of them failed. Running out of ideas.
Just noticed somebody opened a bug report. Hmmm. Wonder if this was in response to this post…
https://github.com/emqx/quic/issues/46
Will see if I can add details.
Hmmm. Eventually I probably will want to try the latest version. But I don’t see anything like a changelog documenting breaking changes.
Any ideas what changes I will need to make?
LATER: on second thoughts the changes don’t look particularly significant:
I just tried my code with
{:emqtt, github: "emqx/emqtt", tag: "1.4.2"},
and it works. I took no notes (bad) so I don’t know what the problem was.
About your build problems: works for me, so it must work in Github Actions (when you use the same toolchain, check all versions.).
Latest theory is that it might be related to the cmake version version. Downgrading to an earlier cmake seems to fix it.
Seems like the challenges are
mosquitto has multiple servers running at test.mosquitto.org providing these methods:
The server listens on the following ports:
1883 : MQTT, unencrypted, unauthenticated
1884 : MQTT, unencrypted, authenticated
8883 : MQTT, encrypted, unauthenticated
8884 : MQTT, encrypted, client certificate required
8885 : MQTT, encrypted, authenticated
8887 : MQTT, encrypted, server certificate deliberately expired
… snip: MQTT over websockets
I’d like to get them all working with emqtt, for this I installed mosquitto-clients as a reference implementation:
sudo apt-add-repository ppa:mosquitto-dev/mosquitto-ppa
sudo apt-get update
sudo apt-get install mosquitto mosquitto-clients
after downloading the provided cert and generating my own (see https://test.mosquitto.org/) I can successfully test all of them but those that are authenticated, because I’m missing the credentials, anybody know what to use?
mosquitto_sub -h test.mosquitto.org -p 1883 -t "#"
# TODO - whats the password? --- mosquitto_sub --pw ??? -h test.mosquitto.org -p 1884 -t "#"
mosquitto_sub --cafile mosquitto.org.crt -h test.mosquitto.org -p 8883 -t "#"
mosquitto_sub --cafile mosquitto.org.crt --cert client.crt --key client.key -h test.mosquitto.org -p 8884 -t "#"
EDIT:
emqtt-cli looks almost the same as mosquitto-sub
./emqtt sub -h test.mosquitto.org -p 1883 -t "#"
./emqtt sub --enable-ssl --CAfile mosquitto.org.crt -h test.mosquitto.org -p 8883 -t "#"
./emqtt sub --enable-ssl --CAfile mosquitto.org.crt --cert client.crt --key client.key -h test.mosquitto.org -p 8884 -t "#"
I can’t get SSL to work.
I’ve looked at the opts emqtt-cli generates for
./emqtt sub --enable-ssl --CAfile mosquitto.org.crt -h test.mosquitto.org -p 8883 -t "#"
which is
opts = [
host: 'test.mosquitto.org',
ssl: true,
ssl_opts: [cacertfile: "mosquitto.org.crt"]
]
but I just get a crash:
iex> {:ok, pid} = :emqtt.start_link(opts)
{:ok, #PID<0.221.0>}
iex> :emqtt.connect(pid)
{:error, :closed}
** (EXIT from #PID<0.214.0>) shell process exited with reason: :closed
adding server_name_indication and verify_peer yields the same result.
I can reproduce this in docker elixir:1.11.4 and elixir:1.12.2 for emqtt 1.2 and 1.4.
Just mix new test_proj, then add to deps {:emqtt, github: "emqx/emqtt", tag: "v1.2.0"} and run:
sudo docker run --volume $(pwd):/emqtt -w /emqtt -it elixir:1.11.4 bash
$> iex -S mix