ftpserver.pl: Added support for POP3 NOOP command

tests/ftpserver.pl

@@ -560,6 +560,7 @@ sub protocolsetup {
             'CAPA' => \&CAPA_pop3,
             'DELE' => \&DELE_pop3,
             'LIST' => \&LIST_pop3,
+            'NOOP' => \&NOOP_pop3,
             'QUIT' => \&QUIT_pop3,
             'RETR' => \&RETR_pop3,
             'STAT' => \&STAT_pop3,
@@ -1326,6 +1327,19 @@ sub STAT_pop3 {
     return 0;
 }
 
+sub NOOP_pop3 {
+    my ($args) = @_;
+
+    if ($args) {
+        sendcontrol "-ERR Protocol error\r\n";
+    }
+    else {
+        sendcontrol "+OK\r\n";
+    }
+
+    return 0;
+}
+
 sub QUIT_pop3 {
     sendcontrol "+OK byebye\r\n";