Add support for receiving DTMF tones

.github/workflows/ci.yml

@@ -14,74 +14,85 @@ jobs:
     name: CI on OTP ${{matrix.otp}} / Elixir ${{matrix.elixir}}
     strategy:
       matrix:
-        otp: ['27']
-        elixir: ['1.17']
+        otp: ["27"]
+        elixir: ["1.17"]
     steps:
-    - name: Set up Elixir
-      uses: erlef/setup-beam@v1
-      with:
-        otp-version: ${{matrix.otp}}
-        elixir-version: ${{matrix.elixir}}
-
-    - name: Checkout the code
-      uses: actions/checkout@v4
-
-    - name: Cache dependencies
-      uses: actions/cache@v4
-      with:
-        path: deps
-        key: ${{ runner.os }}-mix-deps-${{ hashFiles('**/mix.lock') }}
-        restore-keys: |
-          ${{ runner.os }}-mix-deps-
-
-    - name: Cache compiled build
-      uses: actions/cache@v4
-      with:
-        path: _build
-        key: ${{ runner.os }}-mix-build-${{ hashFiles('**/mix.lock') }}
-        restore-keys: |
-          ${{ runner.os }}-mix-build-
-          ${{ runner.os }}-mix-
-
-    - name: Cache dialyzer artifacts
-      uses: actions/cache@v4
-      with:
-        path: _dialyzer
-        key: ${{ runner.os }}-dialyzer-${{ hashFiles('**/mix.lock') }}
-        restore-keys: |
-          ${{ runner.os }}-dialyzer-
-
-    - name: Install dependencies
-      run: mix deps.get
-
-    - name: Compile without warnings
-      id: compile
-      run: mix compile --warnings-as-errors
-
-    - name: Check formatting
-      if: ${{ !cancelled() && steps.compile.outcome == 'success' }}
-      run: mix format --check-formatted
-
-    - name: Check with credo
-      if: ${{ !cancelled() && steps.compile.outcome == 'success' }}
-      run: mix credo
-
-    - name: Check with dialyzer
-      if: ${{ !cancelled() && steps.compile.outcome == 'success' }}
-      run: mix dialyzer
-
-    - name: Check docs
-      if: ${{ !cancelled() && steps.compile.outcome == 'success' }}
-      run: mix docs 2>&1 | (! grep -q "warning:")
-
-    - name: Run tests and check test coverage
-      if: ${{ !cancelled() && steps.compile.outcome == 'success' }}
-      id: test
-      run: mix coveralls.json
-
-    - name: Upload test coverage results to Codecov
-      if: ${{ !cancelled() && steps.test.outcome == 'success' }}
-      uses: codecov/codecov-action@v4
-      with:
-        fail_ci_if_error: true,
-        token: ${{ secrets.CODECOV_TOKEN }}
+      - name: "Interfaces"
+        run: |
+          echo "Listing Network Interfaces:"
+          ip link show
+
+      - name: Check if Docker is installed and running on Linux
+        run: |
+          echo "Checking Docker..."
+          docker -v
+          systemctl status docker.service --no-pager
+
+      - name: Set up Elixir
+        uses: erlef/setup-beam@v1
+        with:
+          otp-version: ${{matrix.otp}}
+          elixir-version: ${{matrix.elixir}}
+
+      - name: Checkout the code
+        uses: actions/checkout@v4
+
+      - name: Cache dependencies
+        uses: actions/cache@v4
+        with:
+          path: deps
+          key: ${{ runner.os }}-mix-deps-${{ hashFiles('**/mix.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-mix-deps-
+
+      - name: Cache compiled build
+        uses: actions/cache@v4
+        with:
+          path: _build
+          key: ${{ runner.os }}-mix-build-${{ hashFiles('**/mix.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-mix-build-
+            ${{ runner.os }}-mix-
+
+      - name: Cache dialyzer artifacts
+        uses: actions/cache@v4
+        with:
+          path: _dialyzer
+          key: ${{ runner.os }}-dialyzer-${{ hashFiles('**/mix.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-dialyzer-
+
+      - name: Install dependencies
+        run: mix deps.get
+
+      - name: Compile without warnings
+        id: compile
+        run: mix compile --warnings-as-errors
+
+      - name: Check formatting
+        if: ${{ !cancelled() && steps.compile.outcome == 'success' }}
+        run: mix format --check-formatted
+
+      - name: Check with credo
+        if: ${{ !cancelled() && steps.compile.outcome == 'success' }}
+        run: mix credo
+
+      - name: Check with dialyzer
+        if: ${{ !cancelled() && steps.compile.outcome == 'success' }}
+        run: mix dialyzer
+
+      - name: Check docs
+        if: ${{ !cancelled() && steps.compile.outcome == 'success' }}
+        run: mix docs 2>&1 | (! grep -q "warning:")
+
+      - name: Run tests and check test coverage
+        if: ${{ !cancelled() && steps.compile.outcome == 'success' }}
+        id: test
+        run: mix coveralls.json
+
+      - name: Upload test coverage results to Codecov
+        if: ${{ !cancelled() && steps.test.outcome == 'success' }}
+        uses: codecov/codecov-action@v4
+        with:
+          fail_ci_if_error: true,
+          token: ${{ secrets.CODECOV_TOKEN }}

examples/dtmf/.formatter.exs

@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

examples/dtmf/.gitignore

@@ -0,0 +1,23 @@
+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+dtmf-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/

examples/dtmf/README.md

@@ -0,0 +1,21 @@
+# Dtmf
+
+**TODO: Add description**
+
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed
+by adding `dtmf` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:dtmf, "~> 0.1.0"}
+  ]
+end
+```
+
+Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
+and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
+be found at <https://hexdocs.pm/dtmf>.
+

examples/dtmf/config/config.exs

@@ -0,0 +1,8 @@
+import Config
+
+config :logger, level: :info
+
+# normally you take these from env variables in `config/runtime.exs`
+config :dtmf,
+  ip: {127, 0, 0, 1},
+  port: 8829

examples/dtmf/lib/dtmf.ex

@@ -0,0 +1,15 @@
+defmodule Dtmf do
+  use Application
+
+  @ip Application.compile_env!(:dtmf, :ip)
+  @port Application.compile_env!(:dtmf, :port)
+
+  @impl true
+  def start(_type, _args) do
+    children = [
+      {Bandit, plug: __MODULE__.Router, ip: @ip, port: @port}
+    ]
+
+    Supervisor.start_link(children, strategy: :one_for_one)
+  end
+end

examples/dtmf/lib/dtmf/peer_handler.ex

@@ -0,0 +1,136 @@
+defmodule Dtmf.PeerHandler do
+  require Logger
+
+  alias ExWebRTC.{
+    ICECandidate,
+    MediaStreamTrack,
+    PeerConnection,
+    RTPCodecParameters,
+    SessionDescription
+  }
+
+  @behaviour WebSock
+
+  @ice_servers [
+    %{urls: "stun:stun.l.google.com:19302"}
+  ]
+
+  @audio_codecs [
+    %RTPCodecParameters{
+      payload_type: 111,
+      mime_type: "audio/opus",
+      clock_rate: 48_000,
+      channels: 2
+    },
+    %RTPCodecParameters{
+      payload_type: 112,
+      mime_type: "audio/telephone-event",
+      clock_rate: 8000,
+      channels: 1
+    }
+  ]
+
+  @impl true
+  def init(_) do
+    {:ok, pc} =
+      PeerConnection.start_link(
+        ice_servers: @ice_servers,
+        video_codecs: [],
+        audio_codecs: @audio_codecs
+      )
+
+    state = %{
+      peer_connection: pc,
+      in_audio_track_id: nil
+    }
+
+    {:ok, state}
+  end
+
+  @impl true
+  def handle_in({msg, [opcode: :text]}, state) do
+    msg
+    |> Jason.decode!()
+    |> handle_ws_msg(state)
+  end
+
+  @impl true
+  def handle_info({:ex_webrtc, _from, msg}, state) do
+    handle_webrtc_msg(msg, state)
+  end
+
+  @impl true
+  def handle_info({:EXIT, pc, reason}, %{peer_connection: pc} = state) do
+    # Bandit traps exits under the hood so our PeerConnection.start_link
+    # won't automatically bring this process down.
+    Logger.info("Peer connection process exited, reason: #{inspect(reason)}")
+    {:stop, {:shutdown, :pc_closed}, state}
+  end
+
+  @impl true
+  def terminate(reason, _state) do
+    Logger.info("WebSocket connection was terminated, reason: #{inspect(reason)}")
+  end
+
+  defp handle_ws_msg(%{"type" => "offer", "data" => data}, state) do
+    Logger.info("Received SDP offer:\n#{data["sdp"]}")
+
+    offer = SessionDescription.from_json(data)
+    :ok = PeerConnection.set_remote_description(state.peer_connection, offer)
+
+    {:ok, answer} = PeerConnection.create_answer(state.peer_connection)
+    :ok = PeerConnection.set_local_description(state.peer_connection, answer)
+
+    answer_json = SessionDescription.to_json(answer)
+
+    msg =
+      %{"type" => "answer", "data" => answer_json}
+      |> Jason.encode!()
+
+    Logger.info("Sent SDP answer:\n#{answer_json["sdp"]}")
+
+    {:push, {:text, msg}, state}
+  end
+
+  defp handle_ws_msg(%{"type" => "ice", "data" => data}, state) do
+    Logger.info("Received ICE candidate: #{data["candidate"]}")
+
+    candidate = ICECandidate.from_json(data)
+    :ok = PeerConnection.add_ice_candidate(state.peer_connection, candidate)
+    {:ok, state}
+  end
+
+  defp handle_webrtc_msg({:connection_state_change, conn_state}, state) do
+    Logger.info("Connection state changed: #{conn_state}")
+
+    if conn_state == :failed do
+      {:stop, {:shutdown, :pc_failed}, state}
+    else
+      {:ok, state}
+    end
+  end
+
+  defp handle_webrtc_msg({:ice_candidate, candidate}, state) do
+    candidate_json = ICECandidate.to_json(candidate)
+
+    msg =
+      %{"type" => "ice", "data" => candidate_json}
+      |> Jason.encode!()
+
+    Logger.info("Sent ICE candidate: #{candidate_json["candidate"]}")
+
+    {:push, {:text, msg}, state}
+  end
+
+  defp handle_webrtc_msg({:track, %MediaStreamTrack{kind: :audio, id: id}}, state) do
+    state = %{state | in_audio_track_id: id}
+    {:ok, state}
+  end
+
+  defp handle_webrtc_msg({:rtp, id, nil, packet}, %{in_audio_track_id: id} = state) do
+    dbg(packet)
+    {:ok, state}
+  end
+
+  defp handle_webrtc_msg(_msg, state), do: {:ok, state}
+end

examples/dtmf/lib/dtmf/router.ex

@@ -0,0 +1,15 @@
+defmodule Dtmf.Router do
+  use Plug.Router
+
+  plug(Plug.Static, at: "/", from: :dtmf)
+  plug(:match)
+  plug(:dispatch)
+
+  get "/ws" do
+    WebSockAdapter.upgrade(conn, Dtmf.PeerHandler, %{}, [])
+  end
+
+  match _ do
+    send_resp(conn, 404, "not found")
+  end
+end