diff --git a/Changelog b/Changelog
index b7123ae..5a51588 100644
--- a/Changelog
+++ b/Changelog
@@ -1,3 +1,6 @@
+2023-09-16:
+- added message if a connection is closed.
+
 2022-10-31:
 - fixed use of uninitialized and wrong value.
 
diff --git a/modbussrv.cc b/modbussrv.cc
index d49687a..37286fe 100644
--- a/modbussrv.cc
+++ b/modbussrv.cc
@@ -179,12 +179,18 @@ void ModbusSrv::ServerThread() {
 				char *msg;
 				clients[slot] = tcp;
 				msg = (char*) malloc (255);
-				snprintf (msg, 255, "new connection from %s\n", clients[slot]->GetRemoteAddr().c_str());
+				snprintf (msg, 255, "new connection from %s, use slot:%d\n", clients[slot]->GetRemoteAddr().c_str(), slot);
 				gdk_threads_add_idle(cb_thread_network_text_add, msg);
 			}
 			else {
 				// no free slot, accept and close right away.
-				if (tcp) delete tcp;
+				if (tcp) {
+					char *msg;
+					msg = (char*) malloc (255);
+					snprintf (msg, 255, "no free slot, close connection.\n");
+					gdk_threads_add_idle(cb_thread_network_text_add, msg);
+					delete tcp;
+				}
 			}
 		}
 
@@ -195,6 +201,10 @@ void ModbusSrv::ServerThread() {
 			if (clients[slot] != NULL) {
 				len = clients[slot]->ReadTimeout(inbuffer, MODBUS_IOBUFFER, 0);
 				if (len < 0) {
+					char *msg;
+					msg = (char*) malloc (255);
+					snprintf (msg, 255, "connection on slot %d closed.\n", slot);
+					gdk_threads_add_idle(cb_thread_network_text_add, msg);
 					delete clients[slot];
 					clients[slot] = NULL;
 				}