[636] Correctly handle empty files with "mosquitto_pub -l".

Thanks to Aleksandr Makarov.

Bug: https://github.com/eclipse/mosquitto/issues/676

ChangeLog.txt

@@ -23,6 +23,9 @@ Client library:
 - Fix mosquitto_topic_matches_sub() not correctly matching foo/bar against
   foo/+/#. Closes #670.
 
+Clients:
+- Correctly handle empty files with "mosquitto_pub -l". Closes #676.
+
 Build:
 - Don't run TLS-PSK tests if TLS-PSK disabled at compile time. Closes #636.
 

client/pub_client.c

@@ -34,6 +34,7 @@ Contributors:
 #define STATUS_CONNECTING 0
 #define STATUS_CONNACK_RECVD 1
 #define STATUS_WAITING 2
+#define STATUS_DISCONNECTING 3
 
 /* Global variables for use in callbacks. See sub_client.c for an example of
  * using a struct to hold variables for use in callbacks. */
@@ -410,8 +411,15 @@ int main(int argc, char *argv[])
 					}
 				}
 				if(feof(stdin)){
-					last_mid = mid_sent;
-					status = STATUS_WAITING;
+					if(last_mid == -1){
+						/* Empty file */
+						mosquitto_disconnect(mosq);
+						disconnect_sent = true;
+						status = STATUS_DISCONNECTING;
+					}else{
+						last_mid = mid_sent;
+						status = STATUS_WAITING;
+					}
 				}
 			}else if(status == STATUS_WAITING){
 				if(last_mid_sent == last_mid && disconnect_sent == false){