sendACK method
Implementation
void sendACK(IncomingMessage response) {
OutgoingRequest ack =
OutgoingRequest(SipMethod.ACK, request.ruri, ua, <String, dynamic>{
'route_set': request.getHeaders('route'),
'call_id': request.getHeader('call-id'),
'cseq': request.cseq
});
ack.setHeader('from', request.getHeader('from'));
ack.setHeader('via', request.getHeader('via'));
ack.setHeader('to', response.getHeader('to'));
D = setTimeout(() {
timer_D();
}, Timers.TIMER_D);
transport!.send(ack);
}