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Frequently Asked Questions

Error 408 Request Timeout

 This error means that the phone did not receive a reply from the server(or there is no connectivity with it) and is common with new installations or when changing the network connectivity, i.e. being it 3G/4G or WiFi network.

Check the routing device/ firewall settings

Common reasons include:

  • There is typo (or an extra space) in the host/domain name:


Windows, Mac, Linux and iOS:


Open Zoiper -> Go to Settings -> Accounts -> (your account)

Double check that the setting for "Domain"is correct and does not contain any spaces.






Open Zoiper -> Go to Settings -> Accounts -> (your account)

Double check that the setting for "Host"is correct and does not contain any spaces.




  • There's an issue with your internet connectivity

Please open your browser and check  if you can visit a random website. If not, you have to fix your internet connectivity issue(s) first. If you are not able to do so yourself, we would suggest contacting your ITSP (internet service provider)


  • Your network provider is blocking VoIP calls. (this happens mostly in middle eastern countries)
    •  contact your internet provider and ask if they allow VoIP calls on their network;
    • Use TLS encryption for the SIP signalling, especially when combined with a server running SIP on port 443.(this requires server side support for TLS);
    • use RTP encryption for media;
    • use a third party VPN service;


  • Your router is intercepting and changing the packets as they pass through

Be sure to Disable SIP ALG on the router. A list with problematic routers and solutions can be found here

More detailed instructions:

Zyxel routers: 

Netgear routers:


  • A firewall on your device is blocking the traffic


A list with common firewalls and how to disable them can be found here: 


Please add Zoiper to the list of allowed applications in the macOS firewall. 

Instructions can be found here: 


 Please try disabling the Linux firewall.

We do not have complete instructions on how to configure all possible firewalls on the different Linux distributions.

For Ubuntu, please have a look here.


 If you are using Android and have a firewall installed, please Disable it. 


 If you are using a jailbroken iOS iPhone or iPad, please Disable any firewalls you might have installed.


  • A NAT router in between the softphone and the server is causing some packets to be dropped

Zoiper has a few settings to trick the server into sending the packets to a different IP address or port.

Please try different settings combinations of STUN (enabled or disabled) or rport for signalling (enabled or disabled).


STUN ON - Rport ON



Please note that:

A combination that works on one WiFi access point or 3G/4G network might not work on another.

A combination that works one WiFi or cellular network for a specific VoIP server might not work for another one.

If the above fails, please contact your provider or PBX administrator might be able to tweak a server side setting to make things work.


  • The PBX or SIP Provider  you are trying to connect to is currently down.

Please contact your provider for further assistance;


  • Your PBX is on an internal network, but Zoiper is not on the same network and no VPN is running.

Please make sure Zoiper and the PBX or on the same network or setup a VPN  between the device running Zoiper and your PBX. Please consult with your system administrator for additional help.


iOS and Android:

  • Data usage is blocked for Zoiper on your phone.


Go to the Android Settings -> Apps -> Zoiper -> Data usage

  • Enable background data;
  • Enable unrestricted data usage;


Go to the iOS settings -> Cellular
Scroll to the section "Use cellular data for" and make sure that data is enabled for Zoiper.


Check also if the needed ports by Zoiper are not blocked in your firewall/ routing device.The default ports used by Zoiper are:


SIP port is random above 32000

IAX port is 4569 UDP

RTP port is 8000 and above UDP


Default STUN vallues:

Server hostname /IP

Port : 3478 UDP/TCP

Refresh period : 30