Add function to expose TCP Client connectivity status

lib/tcp/client.ex

@@ -130,6 +130,13 @@ defmodule Modbux.Tcp.Client do
     GenServer.call(pid, :flush)
   end
 
+  @doc """
+  Determine if the Client is connected to a Server.
+  """
+  def connected?(pid) do
+    GenServer.call(pid, :connected?)
+  end
+
   # callbacks
   def init(args) do
     port = args[:tcp_port] || @port
@@ -311,6 +318,11 @@ defmodule Modbux.Tcp.Client do
     {:reply, {:ok, state.pending_msg}, new_state}
   end
 
+  def handle_call(:connected?, _from, state) do
+    connected? = state.socket != nil && state.status == :connected
+    {:reply, connected?, state}
+  end
+
   # only for active mode (active: true)
   def handle_info({:tcp, _port, response}, state) do
     Logger.debug("(#{__MODULE__}, :message_active) response: #{inspect(response)}")

test/tcp/modbus_tcp_client_test.exs

@@ -19,4 +19,15 @@ defmodule ModbuxTcpClientTest do
     assert {:error, :econnrefused} == Client.connect(cpid)
     assert {:error, :closed} == Client.close(cpid)
   end
+
+  test "test Client connectivity status" do
+    {:ok, _spid} = Server.start_link(model: %{}, port: 2000)
+    {:ok, cpid} = Client.start_link(ip: {127, 0, 0, 1}, tcp_port: 2000)
+    assert false == Client.connected?(cpid)
+    assert :ok == Client.connect(cpid)
+    assert true == Client.connected?(cpid)
+    assert :ok == Client.close(cpid)
+    assert false == Client.connected?(cpid)
+    assert :ok == Client.stop(cpid)
+  end
 end