Issue with Websockex and json encoding

Questions / Help
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1

I’m trying to send a message using websockex but I’m getting an error when I try to send out my json string (I used Jason), what could I possibly be missing?

"{\"action\":\"subscribe\",\"options\":{\"accounts\":[\"nano_1qzfp3op48im348qdybmrheu9dogtopj1jyioguq9pyo5i7mkqgo4jaswp4a\"],\"all_local_accounts\":true},\"topic\":\"confirmation\"}"
** (ArgumentError) argument error
    :erlang.send(MitoNode.Client, {:"$websockex_cast", "{\"action\":\"subscribe\",\"options\":{\"accounts\":[\"nano_1qzfp3op48im348qdybmrheu9dogtopj1jyioguq9pyo5i7mkqgo4jaswp4a\"],\"all_local_accounts\":true},\"topic\":\"confirmation\"}"})
    (websockex) lib/websockex/utils.ex:57: WebSockex.Utils.send/2
    (websockex) lib/websockex.ex:398: WebSockex.cast/2
2

:erlang.send/2 only fails when the first argument is an atom and this atom is not registered to a process name.

So you need to make sure, that there is actually a process with the name MitoNode.Client.

Or pass a pid that actually does exist.

But all of this is just guessing, as you have not even provided code, but just an error.

3

Sorry, my bad

Heres the construction of the message.

  def sub() do

    {:ok, message} = %{
    "action" => "subscribe",
    "topic" => "confirmation",
    "options" => %{
      "all_local_accounts" => true,
      "accounts" => [
        "nano_1qzfp3op48im348qdybmrheu9dogtopj1jyioguq9pyo5i7mkqgo4jaswp4a"
      ]
    }
  } |> Jason.encode

    IO.inspect(message)

    WebSockex.cast(__MODULE__, message)
  end

in my supervision tree I just have the child {MitoNode.Client, ["random WebSockex message"]} as per the example but I will try a pid too

4

That just delegates the start of the client to its start_link/1, IIRC.

But in that, do you actually name the started process?

1 Like
5

Man you’re the best. Forgot the opts field in start_link, which of course had a name: field, tried subbing with the atom name I gave it and it works fine now. Thanks for the quick advice!

6

You can also use the pid of the WebSockex process and WebSockex.send_frame/2 to send the data. e.g.

{:ok, pid} = MyWebSockexWrapper.start_link()


msg = Jason.encode!(%{
    "action" => "subscribe",
    "topic" => "confirmation",
    "options" => %{
      "all_local_accounts" => true,
      "accounts" => [
        "nano_1qzfp3op48im348qdybmrheu9dogtopj1jyioguq9pyo5i7mkqgo4jaswp4a"
      ]
    })

WebSockex.send_frame(pid, {:text, msg})