kernel 4.4.36, nbd-server v 3.14 , "Receive control failed (result -32)"

[dusane]

All, I am a newbie, trying to run older ver of nbd on 4.4.36, do i need to use config file for this ?
What am i doing wrong ?

$ mount -t tmpfs -o size=4096K tmpfs /mnt/a
$ dd if=/dev/zero of=/mnt/a/NBDFILE count=$((102410244/512)) status=progress
$ ./nbd-server -C /dev/null 9000 /mnt/a/NBDFILE

** (process:52906): WARNING **: Specifying an export on the command line no longer uses the oldstyle protocol.
$

$ netstat -tnlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:513 0.0.0.0:* LISTEN 45833/xinetd
tcp 0 0 0.0.0.0:514 0.0.0.0:* LISTEN 45833/xinetd
tcp 0 0 0.0.0.0:9000 0.0.0.0:* LISTEN 52907/./nbd-server
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 45834/sshd
$

$ ./nbd-client 10.125.7.152 9000 /dev/nbd0
Warning: the oldstyle protocol is no longer supported.
This method now uses the newstyle protocol with a default exportdev/nbd0 -N nbdfi
Negotiation: ..size = 4MB
bs=1024, sz=4194304 bytes
CTRLR-B (Maintenance Mode):nbd#
CTRLR-B (Maintenance Mode):nbd# netstat -tunlpe
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State User Inode PID/Program name
tcp 0 0 0.0.0.0:513 0.0.0.0:* LISTEN 0 107319 41587/xinetd
tcp 0 0 0.0.0.0:514 0.0.0.0:* LISTEN 0 108340 41587/xinetd
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 0 137875 41588/sshd
$ dmesg | tail
[15206.617344] blk_update_request: I/O error, dev nbd0, sector 0
[15210.156880] block nbd1: Other side returned error (5)
[15210.156884] blk_update_request: I/O error, dev nbd1, sector 0
[16080.795152] block nbd1: Receive control failed (result -32)
[16080.795154] block nbd0: Receive control failed (result -32)
[16080.795198] block nbd0: shutting down socket
[16080.795200] block nbd1: shutting down socket
[20037.627547] block nbd0: Receive control failed (result -32)
[20037.627554] block nbd0: pid 52191, nbd-client, got signal 15
[20037.627556] block nbd0: shutting down socket
$