diff --git a/infrastructure-centred/owlps-aggregator/owlps-aggregator.h b/infrastructure-centred/owlps-aggregator/owlps-aggregator.h
index 0bcf13c..2d9b688 100644
--- a/infrastructure-centred/owlps-aggregator/owlps-aggregator.h
+++ b/infrastructure-centred/owlps-aggregator/owlps-aggregator.h
@@ -30,6 +30,7 @@
 #define ERR_CREATING_SOCKET 2 // Erreur when creating listening socket
 #define ERR_BAD_USAGE 3 // Bad program call
 #define ERR_PARSING_CONFIG_FILE 4 // Error reading the configuration file
+#define ERR_SENDING_INFO 5 // Error sending a message on a socket
 
 
 /* Linked list storing data of couples MAC / sequence number */
diff --git a/infrastructure-centred/owlps-aggregator/owlps-aggregatord.c b/infrastructure-centred/owlps-aggregator/owlps-aggregatord.c
index fefee22..f7cf130 100644
--- a/infrastructure-centred/owlps-aggregator/owlps-aggregatord.c
+++ b/infrastructure-centred/owlps-aggregator/owlps-aggregatord.c
@@ -692,9 +692,9 @@ void listen_for_aps(void)
             fprintf(stderr, "No message received from aggregator!\n") ;
           continue ;
         }
+
 #ifdef DEBUG
-      else
-        fprintf(stderr, "Got a Hello message.\n") ;
+      fprintf(stderr, "Got a Hello message.\n") ;
 #endif // DEBUG
 
       update_ap(message.ap_mac_addr_bytes, message.ap_ip_addr) ;
@@ -870,14 +870,26 @@ void order_send(ap_list *ap)
   struct sockaddr_in serv;
   struct sockaddr_in client ;
   socklen_t serv_len = sizeof(serv);
-  int sockfd =
+  int sockfd ;
+  ssize_t nsent ;
+
+#ifdef DEBUG
+  fprintf(stderr, "Sending an order to %s...\n", ap->ip_addr) ;
+#endif // DEBUG
+
+  sockfd =
     create_udp_sending_socket(ap->ip_addr,
                               cfg_getint(cfg, "autocalibration_port"),
                               &serv, &client) ;
 
   message.order = AUTOCALIBRATION_ORDER_SEND ;
-  sendto(sockfd, (void *)&message, sizeof(message), 0,
-         (struct sockaddr *)&serv, serv_len) ;
+  nsent = sendto(sockfd, (void *)&message, sizeof(message), 0,
+                 (struct sockaddr *)&serv, serv_len) ;
+  if (nsent != (ssize_t) sizeof(message))
+    {
+      perror("Error sending order to the listener") ;
+      exit(ERR_SENDING_INFO) ;
+    }
 
   (void) close(sockfd) ;
 }
@@ -1011,7 +1023,8 @@ void print_usage()
          "\t%s [-f config_file] [-l listening_port] [-i positionner_ip]"
          " [-p positioner_port] [-t aggregate_timeout] [-k keep_timeout]"
          " [-c check_interval] [-o output_file] [-A]"
-         " [-a autocalibration_port]\n"
+         " [-a autocalibration_port] [-K ap_keep_timeout]"
+         " [-C ap_check_interval]\n"
 
          "Main options:\n"
          "\t-h\t\tPrint this help.\n"
@@ -1031,7 +1044,7 @@ void print_usage()
          " 'aggregate_timeout' milliseconds before to be grouped"
          " (default:  %d ms).\n"
          "\t-k keep_timeout\t\tAggregated requests are kept during"
-         " 'keep_timeout' milliseconds (default: %d milliseconds).\n"
+         " 'keep_timeout' milliseconds (default: %d ms).\n"
          "\t-c check_interval\tTime between two checks of the stored"
          " requests (default\t%d microseconds).\n"
 
diff --git a/infrastructure-centred/owlps-listener/owlps-listenerd.c b/infrastructure-centred/owlps-listener/owlps-listenerd.c
index 2544300..03c5288 100644
--- a/infrastructure-centred/owlps-listener/owlps-listenerd.c
+++ b/infrastructure-centred/owlps-listener/owlps-listenerd.c
@@ -918,12 +918,16 @@ void autocalibrate()
         }
 
       if (message.order == AUTOCALIBRATION_ORDER_SEND)
-        send_autocalibration_request() ;
+        {
 #ifdef DEBUG
+          fprintf(stderr, "I just was ordered to send an autocalibration"
+                  " request...\n") ;
+#endif // DEBUG
+          send_autocalibration_request() ;
+        }
       else
         fprintf(stderr,
                 "Autocalibration order unknown: %d.\n", message.order) ;
-#endif // DEBUG
     }
 
   (void) close(listen_sockfd) ;