Since the top search results where outdated and generally a bit unsatisfactory to me, here is my example based on the official Ranch guide for Erlang.
Add Ranch to the list of dependencies in your mix.exs:
defp deps do
[
{:ranch, "~> 2.1"}
]
endIn accordance with the official guide, I created a simple echo server, which just responds with the message one sends to it:
defmodule ElixirRanch.Protocols.Echo do
@behaviour :ranch_protocol
@timeout 5000
def start_link(ref, transport, opts) do
{:ok, spawn_link(__MODULE__, :init, [ref, transport, opts])}
end
def init(ref, transport, _opts) do
{:ok, socket} = :ranch.handshake(ref)
loop(socket, transport)
end
defp loop(socket, transport) do
case transport.recv(socket, 0, @timeout) do
{:ok, data} ->
:ok = transport.send(socket, data)
loop(socket, transport)
_ ->
transport.close(socket)
end
end
endOr, if you like to use GenServer:
defmodule ElixirRanch.Protocols.EchoServer do
use GenServer
@behaviour :ranch_protocol
@timeout 5000
@impl true
def start_link(ref, transport, opts) do
{:ok, :proc_lib.spawn_link(__MODULE__, :init, [{ref, transport, opts}])}
end
@impl true
def init({ref, transport, _opts}) do
{:ok, socket} = :ranch.handshake(ref)
:ok = transport.setopts(socket, active: :once)
:gen_server.enter_loop(__MODULE__, [], {socket, transport}, @timeout)
end
@impl true
def handle_info({:tcp, socket, data}, {socket, transport} = state) do
:ok = transport.send(socket, data)
:ok = transport.setopts(socket, active: :once)
{:noreply, state, @timeout}
end
@impl true
def handle_info(_, {socket, transport} = state) do
transport.close(socket)
{:stop, :shutdown, state}
end
endFor clarity I encapsulated both listeners in a module:
defmodule ElixirRanch.Listeners.Echo do
def child_spec(opts) do
:ranch.child_spec(__MODULE__, :ranch_tcp, opts, ElixirRanch.Protocols.Echo, [])
end
endOr for the GenServer:
defmodule ElixirRanch.Listeners.EchoServer do
def child_spec(opts) do
:ranch.child_spec(__MODULE__, :ranch_tcp, opts, ElixirRanch.Protocols.EchoServer, [])
end
endThen I embedded both listeners into a supervision tree:
defmodule ElixirRanch.ListenerSup do
use Supervisor
def start_link(args) do
Supervisor.start_link(__MODULE__, args)
end
@impl true
def init({}) do
children = [
{ElixirRanch.Listeners.Echo, [{:port, 5555}]},
{ElixirRanch.Listeners.EchoServer, [{:port, 5556}]}
]
Supervisor.init(children, strategy: :one_for_one)
end
endTo put it all together, I added the listener supervisor to an application file...
defmodule ElixirRanch.Application do
use Application
def start(_type, _args) do
children = [
{ElixirRanch.ListenerSup, {}}
]
Supervisor.start_link(children, strategy: :one_for_one)
end
end...and added the application to my mix.exs, so it would start automatically:
def application do
[
mod: {ElixirRanch.Application, []}
]
endClone this repo and get Ranch:
git clone https://github.com/asciibeats/elixir_ranch.git
cd elixir_ranch
mix deps.get
Start the server:
mix run --no-halt
Connect to it:
telnet localhost 5555
Type something, press ENTER and the server should respond with the same message. Wait five seconds for the connection to time out. Change the port to 5556 to try the protocol using GenServer. It should do the same.
I hope you found this little guide helpful!
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