I followed a tutorial and created a gen_tcp server. The code is shown below. The server accepts connections, receives data but the function recv_until_closed (at the very bottom) never matches on {:error, :closed}. Consequently, the connections are never closed. Instead I eventually get timeout errors. I’m testing it by echoing a string to nc localhost 5001 as shown in the video (around 17:30)
This is the first video in the Photohackers in Elixir series
Is there some obvious error in my code that I’m failing to see?
defmodule EventListener.Server do
use GenServer
require Logger
def start_link([] = _opts) do
GenServer.start_link(__MODULE__, :no_state)
end
defstruct [:listen_socket]
@impl true
def init(:no_state) do
listen_options = [
ifaddr: {0, 0, 0, 0},
mode: :binary,
active: false,
reuseaddr: true,
exit_on_close: false
]
case :gen_tcp.listen(5001, listen_options) do
{:ok, listen_socket} ->
state = %__MODULE__{listen_socket: listen_socket}
{:ok, state, {:continue, :accept}}
{:error, reason} ->
{:stop, reason}
end
end
@impl true
def handle_continue(:accept, %__MODULE__{} = state) do
case :gen_tcp.accept(state.listen_socket) do
{:ok, socket} ->
handle_connection(socket)
{:noreply, state, {:continue, :accept}}
{:error, reason} ->
{:stop, reason}
end
end
defp handle_connection(socket) do
case recv_until_closed(socket, _buffer = "") do
{:ok, data} ->
:gen_tcp.send(socket, data)
{:error, reason} ->
Logger.error("Failed to receive data: #{inspect(reason)}");
end
:gen_tcp.close(socket)
end
defp recv_until_closed(socket, buffer) do
case :gen_tcp.recv(socket, 0, 10_000) do
{:ok, data} ->
recv_until_closed(socket, [buffer, data])
{:error, :closed} ->
{:ok, buffer}
{:error, reason} -> {:error, reason}
end
end
end
