diff --git a/libowlps/owlps.h b/libowlps/owlps.h
index b550340..1c90790 100644
--- a/libowlps/owlps.h
+++ b/libowlps/owlps.h
@@ -19,14 +19,13 @@ extern "C" {
 #include <netinet/if_ether.h>
 
 
-// Port on which the positioning request is sent by the mobile:
+// Port on which the positioning and calibration requests are sent by
+// the mobiles (or the listeners for autocalibration requests):
 #define OWL_DEFAULT_REQUEST_PORT 9900
 // Port on which listeners and aggregator communicate:
 #define OWL_DEFAULT_LISTENER_PORT 9901
 // Port on which aggregator and positioning server communicate:
 #define OWL_DEFAULT_AGGREGATION_PORT 9902
-// Port on which autocalibration requests are sent by the listeners:
-#define OWL_DEFAULT_AUTOCALIBRATION_REQUEST_PORT 9903
 // Port on which the aggregator listens for hello messages from the
 // listeners, and the listeners listen for orders from the aggregator:
 #define OWL_DEFAULT_AUTOCALIBRATION_PORT 9904
diff --git a/owlps-listener/owlps-listenerd.c b/owlps-listener/owlps-listenerd.c
index a0a4e7e..9bc2445 100644
--- a/owlps-listener/owlps-listenerd.c
+++ b/owlps-listener/owlps-listenerd.c
@@ -98,7 +98,7 @@ struct {
 #ifdef USE_PTHREAD
   owl_false,
   "",
-  OWL_DEFAULT_AUTOCALIBRATION_REQUEST_PORT,
+  0,
   OWL_DEFAULT_AUTOCALIBRATION_PORT,
   DEFAULT_AUTOCALIBRATION_HELLO_DELAY,
   DEFAULT_AUTOCALIBRATION_DELAY,
@@ -327,9 +327,9 @@ int parse_config_file(int argc, char **argv)
       // Destination IP address of the autocalibration requests (default:
       // none, but will be set to aggregation_ip in the config check):
       CFG_STR("autocalibration_ip", "", CFGF_NONE),
-      // Port on which autocalibration requests are sent:
-      CFG_INT("autocalibration_request_port",
-              OWL_DEFAULT_AUTOCALIBRATION_REQUEST_PORT, CFGF_NONE),
+      // Port on which autocalibration requests are sent (default: 0,
+      // but will be set to listening_port in the config check):
+      CFG_INT("autocalibration_request_port", 0, CFGF_NONE),
       // Port on which autocalibration data are exchanged:
       CFG_INT("autocalibration_port", OWL_DEFAULT_AUTOCALIBRATION_PORT,
               CFGF_NONE),
@@ -650,7 +650,7 @@ int check_configuration()
           if (VERBOSE_WARNING)
             fprintf(stderr, "Warning! Bad autocalibration_request_port:"
                     " failing back to the default value.\n") ;
-          SET_AUTOCALIBRATION_REQUEST_PORT(OWL_DEFAULT_AUTOCALIBRATION_REQUEST_PORT) ;
+          SET_AUTOCALIBRATION_REQUEST_PORT(GET_LISTENING_PORT()) ;
         }
       if (GET_AUTOCALIBRATION_PORT() < 1 ||
           GET_AUTOCALIBRATION_PORT() > 65535)
@@ -1529,7 +1529,7 @@ void print_usage()
          "\t-I autocalib_ip\t\tDestination IP of the autocalibration"
          " requests\n\t\t\t\t(default: aggregation_ip).\n"
          "\t-P autocalib_req_port\tPort on which autocalibration"
-         " requests are sent\n\t\t\t\t(default: %d).\n"
+         " requests are sent\n\t\t\t\t(default: listening_port).\n"
          "\t-a autocalib_port\tPort on which autocalibration data (hello"
          " &\n\t\t\t\torders) are exchanged with the aggregation"
          "\n\t\t\t\tserver (default: %d).\n"
@@ -1556,7 +1556,6 @@ void print_usage()
          DEFAULT_CONFIG_FILE,
          OWL_DEFAULT_REQUEST_PORT,
          OWL_DEFAULT_LISTENER_PORT,
-         OWL_DEFAULT_AUTOCALIBRATION_REQUEST_PORT,
          OWL_DEFAULT_AUTOCALIBRATION_PORT,
          DEFAULT_AUTOCALIBRATION_HELLO_DELAY,
          DEFAULT_AUTOCALIBRATION_DELAY,