VoIP/SIP telephony: I can make calls, but cannot receive them
To be able to make calls over VoIP, a number of ports in your firewall have to be open. This is necessary because otherwise VoIP traffic would be blocked. To be certain when you have connection problems that your firewall is not blocking incoming calls, the best thing to do is switch off your firewall. There are various types of firewall, and these are usually subdivided into 'software firewalls' and 'hardware firewalls'. It is possible that you have both.
This firewall (personal firewall) is a program that is installed on your PC.
A (WLan) router usually has a built-in firewall, although there are also dedicated hardware firewalls.
These firewalls can be accessed in various ways. If necessary, consult with your system manager to have your firewall adjusted.
Open the following ports in your firewall:
- SIP: 5060 / TCP
- SIP: 5060 / UDP
- RTP: 10000 - 20000 / UDP