pfSense

It's not possible to set the variables 'listenporthttp' and 'listenporthttps' via WebGUI
and there is no mention in the docs
looks like a legacy code:

grep listenporthttp:

captiveportal.inc:              if (!empty($cpcfg['listenporthttps'])) {
captiveportal.inc:                      $listenporthttps = $cpcfg['listenporthttps'];
captiveportal.inc:                      $listenporthttps = 8001 + $cpcfg['zoneid'];
captiveportal.inc:                      $crt, $key, $ca, "nginx-{$cpzone}-CaptivePortal-SSL.pid", $listenporthttps, "/usr/local/captiveportal",
captiveportal.inc:      if (!empty($cpcfg['listenporthttp'])) {
captiveportal.inc:              $listenporthttp = $cpcfg['listenporthttp'];
captiveportal.inc:              $listenporthttp = 8000 + $cpcfg['zoneid'];
captiveportal.inc:              "", "", "", "nginx-{$cpzone}-CaptivePortal.pid", $listenporthttp, "/usr/local/captiveportal",
captiveportal.inc:      if (!empty($config['captiveportal'][$cpzone]['listenporthttp'])) {
captiveportal.inc:              $listenporthttp = $config['captiveportal'][$cpzone]['listenporthttp'];
captiveportal.inc:              $listenporthttp = 8000 + $cpzoneid;
captiveportal.inc:              if (!empty($config['captiveportal'][$cpzone]['listenporthttps'])) {
captiveportal.inc:                      $listenporthttps = $config['captiveportal'][$cpzone]['listenporthttps'];
captiveportal.inc:                      $listenporthttps = 8001 + $cpzoneid;
captiveportal.inc:                          "fwd 127.0.0.1,{$listenporthttps} tcp from any to any dst-port 443 in");
captiveportal.inc:          "fwd 127.0.0.1,{$listenporthttp} tcp from any to any dst-port 80 in");
captiveportal.inc:              $listenporthttps = $cpcfg['listenporthttps'] ? $cpcfg['listenporthttps'] : ($cpcfg['zoneid'] + 8001);
captiveportal.inc:              if ($listenporthttps != 443) {
captiveportal.inc:                      $ourhostname .= ":" . $listenporthttps;
captiveportal.inc:              $listenporthttp = $cpcfg['listenporthttp'] ? $cpcfg['listenporthttp'] : ($cpcfg['zoneid'] + 8000);
captiveportal.inc:              if ($listenporthttp != 80) {
captiveportal.inc:                      $ourhostname .= ":" . $listenporthttp;
filter.inc:                             $listenporthttps = $cpcfg['listenporthttps'] ? $cpcfg['listenporthttps'] : 8000 + ($cpcfg['zoneid'] + 1);
filter.inc:                             $listenporthttp  = $cpcfg['listenporthttp']  ? $cpcfg['listenporthttp']  : 8000 + $cpcfg['zoneid'];
filter.inc:                             $portalias = $listenporthttps;
filter.inc:                             $portalias .= " {$listenporthttp}";