So the actual experience using a SIP app on the smartphone often is somehow like: “ The softclient did register fine while my iPhone was logged in to my home WiFi but the connection broke on the cellular network and when I was connected to the airport’s WiFi the connection worked, but on calls incoming audio didn’t work”. Sometimes your phone gets a carrier-grade NAT IPv4 address, sometimes you get a dual-stack IPv6 IP in addition which the OS prefers if the server speaks IPv6 (-> no NAT!) and sometimes important ports are blocked. When you try to use a SIP softclient app on a smartphone you’re most likely constantly switching between various network environments: The cellular network, work and home WiFi, public WiFis, roamed cellular networks when travelling in other countries, etc. Usually you fix these by trial and error for your local network - but things are different on a Smartphone. The problemĬonnecting a VoIP client (like a PBX, a desk phone, a softclient) to a SIP provider’s servers can fail for a multitude of reasons (blocked ports on the router or corporate firewall, NAT traversal, etc). A practical setup for using a Sipgate VoIP account with a Softphone client on the iPhone.
