diff --git a/homeassistant/components/wiffi/config_flow.py b/homeassistant/components/wiffi/config_flow.py
index f9456f25df2..79f26d82585 100644
--- a/homeassistant/components/wiffi/config_flow.py
+++ b/homeassistant/components/wiffi/config_flow.py
@@ -38,6 +38,8 @@ class WiffiFlowHandler(config_entries.ConfigFlow, domain=DOMAIN):
             return self._async_show_form()
 
         # received input from form or configuration.yaml
+        await self.async_set_unique_id(user_input[CONF_PORT])
+        self._abort_if_unique_id_configured()
 
         try:
             # try to start server to check whether port is in use
diff --git a/homeassistant/components/wiffi/strings.json b/homeassistant/components/wiffi/strings.json
index d4dc66972c7..ebc5dd67a20 100644
--- a/homeassistant/components/wiffi/strings.json
+++ b/homeassistant/components/wiffi/strings.json
@@ -10,6 +10,7 @@
     },
     "abort": {
       "addr_in_use": "Server port already in use.",
+      "already_configured": "Server port is already configured.",
       "start_server_failed": "Start server failed."
     }
   },
diff --git a/homeassistant/components/wiffi/translations/en.json b/homeassistant/components/wiffi/translations/en.json
index 046f37de2c7..6732e5102da 100644
--- a/homeassistant/components/wiffi/translations/en.json
+++ b/homeassistant/components/wiffi/translations/en.json
@@ -2,6 +2,7 @@
     "config": {
         "abort": {
             "addr_in_use": "Server port already in use.",
+            "already_configured": "Server port is already configured.",
             "start_server_failed": "Start server failed."
         },
         "step": {