Issues with iPhone App connecting to 3CX

[DGZ]

Hi,

Hopefully I can explain this with enough details as it is a bit of a strange one.

Our 3CX is self hosted and working fine for all other staff. I now have two staff who when then open the 3CX app on their iPhones, it just won't connect. Both staff have just recently had their home internet upgraded from FTTN to FTTP (based in Australia). For Staff1, no change of any equipment, for Staff2, they setup a new modem. This is through Telstra using the Telstra Smart Modems. Have tested this with both the Gen3 and Gen4 modems.

This is the pattern of what is happening:

When at home:
If connected to WiFi network - 3CX shows Connecting... and nothing else happen, simple won't connect
if they turn off the WiFi at home and switch over to the 4G network, the phone will then connect
The Mail App connected to an Exchange server also does the same (not connecting) on the WiFi but does work on 4G network
All other app, web pages, speedtests, etc work on the phone when connected to the WiFi - just 3CX and Mail to Exchange

If they go to another location and use the WiFi there, 3CX will connect and work successfully - nothing changed on the phone apart from being on a different network so I know the 3CX app is setup and working correctly.

What we have tried:
* Turning off IPv6 on WiFi network
* Testing with a different modem at home - made no difference
* Disconnecting all other devices off the modem/WiFi - made no difference
* There are no VPNs setup on the phone to cause conflicts
* Remove the account and add it back
* Uninstall the app and add it back again

It is very strange that it appears to be something very specific to the base connection at the house as everything else has been changed for them.

I have had somebody recently suggest checking into the MTU packet size on the modem - has anybody had issues with this on their setups?

Thanks
Dean

 

[DimitrisL_3CX]

Hello @DGZ,

From your description, I can understand that this is a connectivity issue from the specific home network.
I would suggest running a capture from their modem, if there is access, and also contacting their ISP to check this.
The Mobile App uses HTTPS and port 5090 from the client to the PBX to see if there is connectivity.

 

[Colorado VoIP]

I've ran into issues with comcast's DNS blacklisting our custom FQDN for the older customers (think pre-3cx domain availability I do believe), took down their entire office's ability to connect to the system. Had to put manual DNS entries in their local onsite servers to reconnect everyone to the system. In process of eliminating that headache permanently and moving to 3cx domains as time allows.

If you're running custom domain names, it might be on a blacklist with that ISP.

 

[DGZ]

Hello @DGZ,

From your description, I can understand that this is a connectivity issue from the specific home network.
I would suggest running a capture from their modem, if there is access, and also contacting their ISP to check this.
The Mobile App uses HTTPS and port 5090 from the client to the PBX to see if there is connectivity.

Hi,

Thanks for the info, it is at the staff member home so I will try and arrange to get over there to do some testing. I have checked the firewall on the modem (as I have remote access to is) and even did a test with it off and still no connection. Will do a search on those two ports and see what I can find

Thanks
Dean

 

[DGZ]

I've ran into issues with comcast's DNS blacklisting our custom FQDN for the older customers (think pre-3cx domain availability I do believe), took down their entire office's ability to connect to the system. Had to put manual DNS entries in their local onsite servers to reconnect everyone to the system. In process of eliminating that headache permanently and moving to 3cx domains as time allows.

If you're running custom domain names, it might be on a blacklist with that ISP.

Hi,

Thanks for the suggestion, I will check with the ISP. Strange part is it connects OK at another location using the same ISP but with them, I won't rule out anything.

I think I am running on the 3CX domain - the phones have ourname.3cx.com.au listed as the server name in account if this is what you mean? I am still new to 3CX so have a bit of a learning curve to get past.

Thanks
Dean

 

[SteveITS]

Several times we’ve seen Comcast router/modems block a specific IP and even IP: port, IIRC. Try just powering off their modem for 30 seconds.

 

[Colorado VoIP]

Several times we’ve seen Comcast router/modems block a specific IP and even IP: port, IIRC. Try just powering off their modem for 30 seconds.

comcast just lives in their own little world. but now realizing the OP is not in USA just adds to the mystery of what their local ISP is doing.

 

[brendan.dodd@nextcomtech.]

Check if they have Private Relay enabled on their iPhone