Hosts from secured network cannot connect to server "Invalid response(code 503)"

[zuri111]

Hi
I am using Portal project for remote support with SDK V9.5
In a client of mine his network is behind a secure firewall
all hosts in this network cannot connect to the gateway and reporting "Invalid response from the Gateway (code 503)"
I know that the portal project is not supported but it seems to me that this problem is not portal specific and the "non blocking" feature is not working in this case.
I tried connecting the hosts to the server thru different ports with same results.
any help will be appreciated.
From the host log files
RTC V9.5 (Portal V5.10)
======
on host service stop
2019-07-05 06:33:39.924; TRtcSocketHttpClientProvider.ReleaseMe (11.111.11.11:443) TIMEOUT!
Service running
2019-07-05 06:38:07.271; --------------------------
2019-07-05 06:38:07.272; Host Launcher started.
2019-07-05 06:38:07.381; STARTING a new HOST instance ...
2019-07-05 06:38:12.404; STARTING a new HOST instance ...
2019-07-05 06:38:17.436; STARTING a new HOST instance ...
(endless every 5 second "STARTING a new HOST instance ...")

Old RTC (~V6) (Portal V3.71)
======
2019-07-04 11:14:12.309; Settings loaded successfully.
2019-07-04 11:14:12.309; Auto login as app specified
2019-07-04 11:14:12.379; PClientError: Invalid response from the Gateway (code 503).
2019-07-04 11:14:12.379; PClientFatalError: Invalid response from the Gateway (code 503).
2019-07-04 11:14:14.529; PClientError: Invalid response from the Gateway (code 503).
2019-07-04 11:14:14.529; PClientFatalError: Invalid response from the Gateway (code 503).
2019-07-04 11:14:15.509; PClientError: Invalid response from the Gateway (code 503).
2019-07-04 11:14:15.509; PClientFatalError: Invalid response from the Gateway (code 503).
2019-07-04 11:14:19.479; Process terminated
2019-07-04 11:14:19.479; ================================================================================
2019-07-04 12:33:48.717; CLOSE signal received!
2019-07-04 12:33:48.717; Process terminated
2019-07-04 12:33:48.717; ================================================================================
2019-07-04 12:33:48.717; error in SaveSetup

Gateway not registering anything

Let me add
This remote support apps are also blocked (cannot get server ID)
teamviewer, showmypc, anydesk, Deskgate, ISLOnline, wayknow

This app CAN make remote session
AeroAdmin

[D.Tkalcec (RTC)]

Solution: Get AeroAdmin

In a secure network, you will always have some methods that work and some that don't. If there was a simple solution for custom-built Clients to get through every kind of a firewall as if it was nothing, then there would be no point in using a firewall. Right? Just think about that for a moment. If you want your Client software to get through a firewall without the firewall knowing about it, then your options are to find a hole in the wall, or ... ask your customer to add your Server IP and Port number to their firewalls exception rule (whitelist), so that your Clients can connect through the firewall without hitting the wall.

[zuri111]

Sadly my client cannot make changes to the firewall
Thanks anyway