Using -x now sets the clients to use MQTT v5.0.

ChangeLog.txt

@@ -153,6 +153,7 @@ Clients:
 - Add float printing option to mosquitto_sub.
 - Fix `-f` and `-s` options in mosquitto_rr.
 - Add websockets support.
+- Using `-x` now sets the clients to use MQTT v5.0.
 
 Build:
 - Increased CMake minimal required version to 3.14, which is required for the

client/client_shared.c

@@ -1294,6 +1294,7 @@ int client_config_line_proc(struct mosq_config *cfg, int pub_or_sub, int argc, c
 						cfg->session_expiry_interval = UINT32_MAX;
 					}
 				}
+				cfg->protocol_version = MQTT_PROTOCOL_V5;
 			}
 			i++;
 		}else{

man/mosquitto_pub.1.xml

@@ -708,7 +708,8 @@
 				<term><option>-x</option></term>
 				<listitem>
 					<para>Set the session-expiry-interval property on the CONNECT packet.
-						Applies to MQTT v5 clients only. Set to 0-4294967294 to specify
+						If you use this option, the client will be set to be an MQTT v5
+						client. Set to 0-4294967294 to specify
 						the session will expire in that many seconds after the client
 						disconnects, or use -1, 4294967295, or ∞ for a session that does
 						not expire. Defaults to -1 if -c is also given, or 0 if -c not

man/mosquitto_rr.1.xml

@@ -731,7 +731,8 @@
 				<term><option>-x</option></term>
 				<listitem>
 					<para>Set the session-expiry-interval property on the CONNECT packet.
-						Applies to MQTT v5 clients only. Set to 0-4294967294 to specify
+						If you use this option, the client will be set to be an MQTT v5
+						client. Set to 0-4294967294 to specify
 						the session will expire in that many seconds after the client
 						disconnects, or use -1, 4294967295, or ∞ for a session that does
 						not expire. Defaults to -1 if -c is also given, or 0 if -c not

man/mosquitto_sub.1.xml

@@ -878,7 +878,8 @@ mosquitto_sub -t 'bbc/#' -T bbc/bbc1 --remove-retained</programlisting>
 				<term><option>-x</option></term>
 				<listitem>
 					<para>Set the session-expiry-interval property on the CONNECT packet.
-						Applies to MQTT v5 clients only. Set to 0-4294967294 to specify
+						If you use this option, the client will be set to be an MQTT v5
+						client. Set to 0-4294967294 to specify
 						the session will expire in that many seconds after the client
 						disconnects, or use -1, 4294967295, or ∞ for a session that does
 						not expire. Defaults to -1 if -c is also given, or 0 if -c not