according to documentation (bug occurs with pa10 and pa11)
https://www.freedesktop.org/wiki/Software/PulseAudio/Documentation/User/Modules/#index39h3
"sap_address
The address used to listen for SAP announcements, defaults to 224.0.0.56. It can be either a multicast group or a unicast address."

when sap_address=<unicast> is specified such as 192.168.2.101, pulseaudio fails with a message that this address is not acceptable.

The sender can still be set to a unicast address
(load-module module-rtp-send source=<source> source_ip=192.168.2.101 destination_ip=192.168.2.105)

load-module module-rtp-recv sink=<sink> sap_address=192.168.2.101 latency_msec=50
is not acceptable, 

however "load-module module-rtp-recv sink=alsa_output.pci-0000_00_1b.0.analog-stereo sap_address=0.0.0.0 latency_msec=50" works.

if sap_adresss is not set to 0.0.0.0 then the only way for it to work would be to allow the default to be the destination(the multicast address).

If the multicast address is specified on the receiver side with sap_address, it works. The multicast address of course also works when not specified.

just to make clear,
tcpdump demonstrates the unicast address 192.168.2.101 is being sent to but is only playable on the receiver side if sap_address is set to 0.0.0.0

The documentation can also be slightly improved to mention that the rtp sender be set to an rtp sink.monitor.

"It reads audio data from an existing source and forwards it to the network encapsulated in RTP. " should mention that the "source" not be a final sink device otherwise it wouldn't work.


thanks