diff --git a/server/lib/server/application.ex b/server/lib/server/application.ex
index 89b5bd5..6e1b1f5 100644
--- a/server/lib/server/application.ex
+++ b/server/lib/server/application.ex
@@ -24,7 +24,9 @@ defmodule Server.Application do
     # See https://hexdocs.pm/elixir/Supervisor.html
     # for other strategies and supported options
     opts = [strategy: :one_for_one, name: Server.Supervisor]
-    Supervisor.start_link(children, opts)
+    result = Supervisor.start_link(children, opts)
+    with {:ok, _} <- result, do: Server.Hosts.mark_all_offline()
+    result
   end
 
   # Tell Phoenix to update the endpoint configuration
diff --git a/server/lib/server_web/channels/agent_socket.ex b/server/lib/server_web/channels/agent_socket.ex
new file mode 100644
index 0000000..c068a87
--- /dev/null
+++ b/server/lib/server_web/channels/agent_socket.ex
@@ -0,0 +1,12 @@
+defmodule ServerWeb.AgentSocket do
+  @moduledoc "Entry socket for agents. Actual authentication happens in HostChannel.join/3."
+  use Phoenix.Socket
+
+  channel "host:*", ServerWeb.HostChannel
+
+  @impl true
+  def connect(_params, socket, _connect_info), do: {:ok, socket}
+
+  @impl true
+  def id(_socket), do: nil
+end
diff --git a/server/lib/server_web/endpoint.ex b/server/lib/server_web/endpoint.ex
index c4aa06f..d42b3b9 100644
--- a/server/lib/server_web/endpoint.ex
+++ b/server/lib/server_web/endpoint.ex
@@ -15,6 +15,10 @@ defmodule ServerWeb.Endpoint do
     websocket: [connect_info: [session: @session_options]],
     longpoll: [connect_info: [session: @session_options]]
 
+  socket "/socket", ServerWeb.AgentSocket,
+    websocket: [timeout: 45_000],
+    longpoll: false
+
   # Serve at "/" the static files from "priv/static" directory.
   #
   # You should set gzip to true if you are running phx.digest