Ace

Ace server for managing TCP endpoints and connections.

I tackled this project as an interesting Elixir exercise and to learn about TCP. The code is designed to be accessible and is thoroughly commented.

For more details look at Ace 0.1.

If you are looking for a production webserver I would recommend one of:

Introduction

TCP endpoints are started with a pool of acceptors. Servers are started on demand for each client connection.

Many servers one client, NOT many clients one server.

Ace is responsible for managing server processes. Server modules describe the communication patterns with clients.

Documentation for Ace is available on hexdoc

Installation

Available on Hex, the package can be installed as:

  1. Add ace to your list of dependencies in mix.exs:

    def deps do
      [{:ace, "~> 0.6.3"}]
    end

Usage

Ace manages TCP connections by refering to a user defined server behaviour. An Ace server must implement 4 callbacks:

  • init(connection, configuration) for establishing a new connection.
  • handle_packet(packet, state) to handle incomming TCP packets.
  • handle_info(message, state) to handle application messages sent to the server.
  • terminate to do any cleanup when the connection is closed.

Server

Example server.

defmodule MyServer do
  def init(_connection, state = {:greeting, greeting}) do
    {:send, greeting, state}
  end

  def handle_packet(inbound, state) do
    {:send, "ECHO: #{String.strip(inbound)}\r\n", state}
  end

  def handle_info({:notify, notification}, state) do
    {:send, "#{notification}\r\n", state}
  end

  def terminate(_reason, _state) do
    IO.puts("Socket connection closed")
  end
end

Defining MyServer above we can use it to start an Ace endpoint.

Quick start

From the console, start mix.

iex -S mix

In the iex console, start a TCP endpoint.

app = {MyServer, {:greeting, "WELCOME"}}
{:ok, pid} = Ace.TCP.start_link(app, port: 8080)

Embedded endpoints

It is not a good idea to start unsupervised processes. For this reason an Ace endpoint can be added to you application supervision tree.

children = [
  worker(Ace.TCP, [{MyServer, {:greeting, "WELCOME"}}, [port: 8080]])
]
Supervisor.start_link(children, opts)

See “01 Quote of the Day” for an example setup.

Connect

Use telnet to communicate with the server.

telnet localhost 8080

Wihin the telnet terminal.

# once connected
WELCOME
hi
ECHO: hi

In the iex session.

send(server, {:notify, "BOO!"})

back in telnet terminal.

BOO!

The plan

  1. To take this obviously deficient TCP echo server that I wrote as a beginner elixir developer and create a fully fledged HTTP server.
  2. Keep reasonable notes of progress so others can learn about how to build a web server in elixir.
  3. See what progress I have made in a year as an elixir developer.

Ace 0.1 (TCP echo)

The simplest TCP echo server that works. Checkout the source of version 0.1.0. The change log documents all enhancements to this prototype server.

Using Vagrant

Vagrant manages virtual machine provisioning. Using Vagrant allows you to quickly get started with Ace without needing to install Elixir/erlang on you machine.

If you do not know vagrant, or have it on your machine, I would suggest just installing Elixir on your machine and ignoring this section.

vagrant up

vagrant ssh

cd /vagrant

From this directory instructions will be that same as users running Elixir on their machine.

Contributing

Before opening a pull request, please open an issue first.

Once we’ve decided how to move forward with a pull request:

$ git clone git@github.com:CrowdHailer/Ace.git
$ cd Ace
$ mix deps.get
$ mix test
$ mix dialyzer.plt
$ mix dialyzer

Once you’ve made your additions, mix test passes and mix dialyzer reports no warnings, go ahead and open a PR!

Resources I used to get this far