Maybe it is better to send this to dev list.
Unable to send/receive file using bytestreams instead of ibb in intranet(test in one PC with two client),
while spark 2.7-snapshot could(2.6.3 could not) at the same PC.
System: Win7 x64 SP1 + Jre 8
Server: openfire 3.9.1(remote)
Client:jitsi 2.4.4997/spark 2.6.3 /2.7