diff --git a/infrastructure-centred/owlps-listener/owlps-listenerd.c b/infrastructure-centred/owlps-listener/owlps-listenerd.c
index b9c2d67..3d3dd39 100644
--- a/infrastructure-centred/owlps-listener/owlps-listenerd.c
+++ b/infrastructure-centred/owlps-listener/owlps-listenerd.c
@@ -397,6 +397,38 @@ void check_configuration()
                 " the aggregation IP as the destination of"
                 " autocalibration requests.\n") ;
     }
+
+  // Port numbers //
+  if (GET_AGGREGATION_PORT() < 1 || GET_AGGREGATION_PORT() > 65535)
+    {
+      if (GET_VERBOSE())
+        fprintf(stderr, "Warning! Bad aggregation_port:"
+                " failing back to the default value.\n") ;
+      SET_AGGREGATION_PORT(AGGREGATE_DEFAULT_PORT) ;
+    }
+  if (GET_LISTENING_PORT() < 1 || GET_LISTENING_PORT() > 65535)
+    {
+      if (GET_VERBOSE())
+        fprintf(stderr, "Warning! Bad listening_port:"
+                " failing back to the default value.\n") ;
+      SET_LISTENING_PORT(LOC_REQUEST_DEFAULT_PORT) ;
+    }
+  if (GET_AUTOCALIBRATION_REQUEST_PORT() < 1 ||
+      GET_AUTOCALIBRATION_REQUEST_PORT() > 65535)
+    {
+      if (GET_VERBOSE())
+        fprintf(stderr, "Warning! Bad autocalibration_request_port:"
+                " failing back to the default value.\n") ;
+      SET_AUTOCALIBRATION_REQUEST_PORT(DEFAULT_AUTOCALIBRATION_REQUEST_PORT) ;
+    }
+  if (GET_AUTOCALIBRATION_PORT() < 1 ||
+      GET_AUTOCALIBRATION_PORT() > 65535)
+    {
+      if (GET_VERBOSE())
+        fprintf(stderr, "Warning! Bad autocalibration_port:"
+                " failing back to the default value.\n") ;
+      SET_AUTOCALIBRATION_PORT(DEFAULT_AUTOCALIBRATION_PORT) ;
+    }
 }