There's presently no way (that I have found) through the high-level API to specify that the loopback address should be included as a host candidate in the ICE transport without modifying pjsua itself. I need this feature as I'm working on a product which provides media streams from connected devices to an in-browser application that *may* be run with no network connection (e.g., in highly remote locations). In such cases the ICE transport doesn't provide any candidates by default, as it has no active network interfaces to include. The documentation for on_create_media_transport suggests it's possible to replace the existing media transport for a call with an entirely new one. I'm attempting to do this with the ICE transport when provided with a particular flag. However, while mentioned in the documentation, there appear to be no examples of this being done anywhere I can find, and so I am stuck throwing things against the wall to see if they stick. I have attempted any number of approaches and received different errors depending on the circumstances. One approach was to replace the transport associated with the call_media (call->media[media_idx].tp = new_tp) while returning NULL from the on_create_media_function. This results in the call being terminated because the media is "Temporarily Unavailable" (presumably). The other approach, which I believe to be the correct one, is to detach the current transport from the media stream and return the new one from the on_create_media_transport function. Unfortunately, when I do this I get a "SIP Failure Code" (406 Not Acceptable). I *believe* this is because I wind up with repeated candidate lines (at least that is what appears to happen when preparing the SDP response). Attached you will find a copy of the log output from PJSIP, as well as my on_create_media_transport function (which is mostly ripped from pjsua-lib's pjsua_media.c's create_ice_media_transport function). I would appreciate any help y'all could offer.