broker tests: Test address with no port, hostname address.

Former as per suggestion
Yakifo#72 (comment)

Latter because I'm not sure how the `asyncio.create_server` and similar
libraries react to being given a host name.  (Maybe it does a reverse
DNS look-up, maybe not… do users really want to trust that reverse DNS
gets the right IP?)

tests/test_broker.py

@@ -20,6 +20,7 @@
     EVENT_BROKER_MESSAGE_RECEIVED,
     ListenerType,
     ListenerConfig,
+    BrokerException,
 )
 from amqtt.client import MQTTClient, ConnectException
 from amqtt.mqtt import (
@@ -103,6 +104,28 @@ def test_lc_decode_v6_addr():
     assert lc.port == 1883
 
 
+def test_lc_decode_no_port():
+    """
+    Test an address without a port raises an error
+    """
+    try:
+        ListenerConfig(ListenerType.TCP, bind="[::]")
+        assert False, "Should not have been accepted"
+    except BrokerException as e:
+        assert str(e) == "Invalid address given in bind value: '[::]'"
+
+
+def test_lc_decode_hostname():
+    """
+    Test a hostname (not IP) raises an error
+    """
+    try:
+        ListenerConfig(ListenerType.TCP, bind="localhost:1883")
+        assert False, "Should not have been accepted"
+    except BrokerException as e:
+        assert str(e) == "Invalid address given in bind value: 'localhost:1883'"
+
+
 @pytest.mark.asyncio
 async def test_start_stop(broker, mock_plugin_manager):
     mock_plugin_manager.assert_has_calls(