WebSockex - An Elixir WebSocket client

The thing that I don’t know about is checking to see if iodata is valid UTF8 for text frames. Currently I’m using String.valid?/1. If I remember correctly it doesn’t work with iodata. If it does, then I am totally wrong and there is no problem at all.

Oh, I haven’t thought about it. Is this check required by the spec?

If it is, something like cowlib/src/cow_ws.erl at master · ninenines/cowlib · GitHub can be adapted to work with iodata.

The validation in cowboy though happens only on the receiving end, it seems.

Honestly, it probably is easier to use IO.iodata_length. Feel free to open an issue or PR.

The thing that I don’t know about is checking to see if iodata is valid UTF8 for text frames. Currently I’m using String.valid?/1. If I remember correctly it doesn’t work with iodata. If it does, then I am totally wrong and there is no problem at all.

It seems like websockex doesn’t support iodata in send_frame?

** (exit) exited in: WebSockex.call(Some.Client, {:text, ["{\"cmd\":", [34, [], "keepalive", 34], ",\"session_id\":", [34, [], 34], ",\"transaction\":", [34, [], "y653PDXvxmGaW+0y4Nab", 34], 125]})
    ** (EXIT) an exception was raised:
        ** (ArgumentError) argument error
            :erlang.byte_size(["{\"cmd\":", [34, [], "keepalive", 34], ",\"session_id\":", [34, [], 34], ",\"transaction\":", [34, [], "y653PDXvxmGaW+0y4Nab", 34], 125])
            (websockex) lib/websockex/frame.ex:296: WebSockex.Frame.get_payload_length_bin/1
            (websockex) lib/websockex/frame.ex:257: WebSockex.Frame.encode_frame/1
            (websockex) lib/websockex.ex:723: WebSockex.sync_send/5
            (stdlib) proc_lib.erl:247: :proc_lib.init_p_do_apply/3
    (websockex) lib/websockex.ex:349: WebSockex.send_frame/2

Wouldn’t it be easier to use IO.iodata_length instead of :erlang.byte_size? Since it works both on binaries and iolists.

iex(8)> data = API.Keepalive.new() |> Jason.encode_to_iodata!() |> IO.iodata_length()
74
iex(9)> data = API.Keepalive.new() |> Jason.encode!() |> IO.iodata_length()
74

Hi @Azolo!

I wonder if it’s possible to use WebSockex with subprotocols? I can’t seem to find any mention of it neither in the docs nor in code …

EDIT:

WebSockex.start_link(url, __MODULE__, state, [
  name: __MODULE__, extra_headers: [{"Sec-WebSocket-Protocol", "my-protocol"}]
])

seems to work fine.

How were you able to connect to the socket.io client? Do you have any sample code?

Ulimit does only increase the softlimit which can never be higher than the hard limit. The hardlimit needs to be increased first, on most systems you can do so via sysctl AFAIR.

Im in mobile so it’s hard to do a proper check right now.

@Azolo thank you for the prompt response… I increased the number of “open files” to 200K but still no luck.
I changed the code to display a specific error in
websockex/websockex/conn.ex

 91   @spec socket_send(__MODULE__.t, binary) :: :ok | {:error, reason :: term}
 92   def socket_send(conn, message) do
 93     case conn.conn_mod.send(conn.socket, message) do
 94       :ok -> :ok
 95       {:error, error} -> {:error, %WebSockex.ConnError{original: "ERR_A"}}
 96     end
 97   end

so it looks like this is triggered in a “SEND”.
How would you recommend to debug the

“conn.conn_mod.send(conn.socket, message)” call?

===== Fragment of code which you can test

  5   def start(server, users) do
  6     all_users = 1..users
  7
  8     Logger.info("Simulator: registering #{users} users...")
  9     all_users
 10     |> Enum.map(fn i ->
 11       Task.async(fn ->
 12         {:ok, client} = WebSockex.start_link("ws://0.0.0.0:4000/socket/websocket", [])

 15       end)
 16     end)
 17     |> Enum.each(&Task.await/1)

I would guess that is probably an OS file descriptor limit, but other than that I don’t know.

Mt best guess would be to try increasing the maximum file descriptors on the server and client using ulimit -n.

@Azolo Is there a OS configuration necessary to be able to create 1K websockets connecting to the same Phoenix instance. I am getting this error

(MatchError) no match of right hand side value:

{:error, %WebSockex.ConnError{original: :closed}}

after about 200 processes created with this code

opts = [

  {:debug, [:trace]},
  {:socket_connect_timeout, Keyword.get(
    opts, :socket_connect_timeout, @socket_connect_timeout)},
  {:socket_recv_timeout, Keyword.get(
      opts, :socket_recv_timeout, @socket_recv_timeout)},
]

    WebSockex.start_link(conn_info, __MODULE__, state, [ {:debug, [:trace]} | opts] )

Hopefully anytime that the process is going to exit for whatever reason.

If there is a time that terminate isn’t called then it is considered a bug.