So, while I've managed to get the registration *mostly* working, there are a couple of things that remain unresolved: 1) We're notified about the transmitted REGISTER message in mod_on_tx_request() callback. However, I don't see a way to obtain the context of the registration there -- for example, the token provided to pjsip_regc_create(). What's the best way to pass some kind of context along with the message to be sent, before calling pjsip_regc_send()? 2) When 401 response for the REGISTER is received, I don't see any callbacks being called. How can I log/process/inspect this response? Thank you, Alex