For v3:
 * Look into bug where lastmsgtime = srcdat->INF_GetLastMessageTime() was somehow 
   negative
 * similar changes to udpv6 transmitter as to udpv4 transmitter

For v4:
 * introduce a basic transmitter which does not have things like a destination list,
   ignore list, accept list
 * similarly: create a basic rtpsession class
 * don't order accepted rtp packets anymore, don't look for duplicates