The odd thing is the sender is specifying the delivery-id, here is the output of PN_TRACE_FRM=1 on the sender side:
[0x86b6580]:0 -> @transfer(20) [handle=0, delivery-id=0, delivery-tag=b"\x00\x00\x00\x00\x00\x00\x00\x00", message-format=0, settled=true, more=false] (5243441) "\x00Sp\xd0\x00\x00\x00\x0b\x00\x..." This is the output from one of the tests, but I can replicate it just using example programs and inputing large amounts of data, yet even with small amounts of data the delivery-tag is still not being set when sent to a reciever. Here is the sender: [0x17471b0]:0 -> @transfer(20) [handle=0, delivery-id=3, delivery-tag=b"\x03\x00\x00\x00\x00\x00\x00\x00", message-format=0, settled=false, more=false] (109) "\x00Sp\xd0\x00\x00\x00\x0b\x00\x00\x00\x05BP\x04@BR\x00\x00Ss\xd0\x00\x00\x00L\x00\x00\x00\x0d@@\xa1$amqp://127.0.0.1:61613/topic://event\xa1\x04Test@@@@\x83\x00\x00\x00\x00\x00\x00\x00\x00\x83\x00\x00\x00\x00\x00\x00\x00\x00@R\x00@\x00Sw\xa1\x01a" Here is the reciever: [0x1de3ac0]:0 <- @transfer(20) [handle=0, delivery-id=5, delivery-tag=b"0", message-format=0] (122) "\x00Sp\xc0\x07\x05BP\x04@BC\x00Ss\xc0G\x0c@@\xa1$amqp://127.0.0.1:61613/topic://event\xa1\x04Test@@@@\x83\x00\x00\x00\x00\x00\x00\x00\x00\x83\x00\x00\x00\x00\x00\x00\x00\x00@C\x00Sw\xa1\x01a\x00Sx\xc1\x17\x02\xa3\x06origin\xa1\x0cmybroker-43c" -- View this message in context: http://qpid.2158936.n2.nabble.com/Proton-c-Null-Messages-tp7625967p7626224.html Sent from the Apache Qpid Proton mailing list archive at Nabble.com.