secure_channel: Use counter module for transaction id

lib/tres/example_handler.ex

@@ -10,13 +10,13 @@ defmodule Tres.ExampleHandler do
               conn_ref: nil
   end
 
-  def start_link([datapath, args]) do
+  def start_link(datapath, args) do
     GenServer.start_link(__MODULE__, [datapath, args])
   end
 
   def init([{datapath_id, aux_id}, _args]) do
     info(
-      "[#{__MODULE__}] Switch Ready: " <>
+      "Switch Ready: " <>
         "datapath_id: #{datapath_id} " <> "aux_id: #{aux_id} " <> "on #{inspect(self())}"
     )
 
@@ -36,14 +36,19 @@ defmodule Tres.ExampleHandler do
     {:noreply, state}
   end
 
+  def handle_info({:switch_disconnected, _reason}, state) do
+    :ok = warn("Switch disconnected")
+    {:stop, :normal, state}
+  end
+
   def handle_info({:switch_hang, _datapath_id}, state) do
-    :ok = warn("[#{__MODULE__}] Switch possible hang: datapath_id: #{state.datapath_id}")
+    :ok = warn("Switch possible hang: datapath_id: #{state.datapath_id}")
     {:noreply, state}
   end
 
   # `Catch all` function is required.
   def handle_info(info, state) do
-    :ok = warn("[#{__MODULE__}] unhandled message #{inspect(info)}: #{state.datapath_id}")
+    :ok = warn("unhandled message #{inspect(info)}: #{state.datapath_id}")
     {:noreply, state}
   end
 
@@ -61,7 +66,7 @@ defmodule Tres.ExampleHandler do
 
   defp handle_desc_stats_reply(desc, datapath_id) do
     info(
-      "[#{__MODULE__}] Switch Desc: " <>
+      "Switch Desc: " <>
         "mfr = #{desc.mfr_desc} " <>
         "hw = #{desc.hw_desc} " <> "sw = #{desc.sw_desc} " <> "for #{datapath_id}"
     )
@@ -70,7 +75,7 @@ defmodule Tres.ExampleHandler do
   defp handle_port_desc_stats_reply(port_desc, datapath_id) do
     for port <- port_desc.ports do
       info(
-        "[#{__MODULE__}] Switch has port: " <>
+        "Switch has port: " <>
           "number = #{port.number} " <>
           "hw_addr = #{port.hw_addr} " <>
           "name = #{port.name} " <>