Hi all - especially Benny ;), after two days of debugging, patching, pondering and scratching my head over IPv6, and what *I* could be doing wrong, I just realised that there is no IPv6 support for SIP TCP sockets in PJSIP yet. I just discovered ticket #1127. ^^ (silly me) But the intarwebs is there to help: someone posted a patch to the asterisk repository: https://code.asterisk.org/code/cru/CR-ASTSCF-16 Does that look like something, that incorporates IPv6 support on PJSIP TCP SIP sockets in a reasonable manner? Thanks for any comments, Sebastian. PS: any chance #1127 is switching from the 2.0 to the 1.12 milestone? Because of Apples restrictions on background operation, people using PJSIP on iOS are effectively bound to TCP instead of UDP.