Actually, My scenario is app goes to suspended state/force killed state, so I got a VOIP push to wake up [not using callkit] and do some HTTP tasks, Some SIP tasks and then setup a UDP socket and communicate with server. HTTP and SIP communication is fine, but when I try to setup that UDP socket on a particular udp port getting can not assign address, fact is interface is active cause other traffic is fine, but not understanding why it works most of the time but fails as well.