signaling busy on_incoming_call

[tmemail@xxxxxx (Thomas Martin)]

Hello Everybody,

this seems to be really simple:

I would like to signal BUSY_HERE ("486") to the caller when I receive the concerned on_incoming_call callback, so that the caller can receive some kind of busy signal.

I've tried both:
			pjsua_call_answer(callID, PJSIP_SC_BUSY_HERE, NULL, NULL);

and also: 		
			pjsua_call_hangup(callID, PJSIP_SC_BUSY_HERE, NULL, NULL);

with no reliable success, i.e. very rarely, the caller receives the BUSY_HERE response, instead, the caller usually just terminates because of a plain time-out - hence, unfortunately, without ever receiving a busy signal. This is independent of the caller's hard- or software.

What am I missing?

Thank you very much in advance!

Best regards,

Thomas