Is the handshake correct?

[akiradeveloper]

https://github.com/NetworkBlockDevice/nbd/blob/master/doc/proto.md

I think buse uses oldstyle negotiation and the spec says server sends these five data.

S: 64 bits, 0x4e42444d41474943 (ASCII 'NBDMAGIC') (also known as the INIT_PASSWD)
S: 64 bits, 0x00420281861253 (cliserv_magic, a magic number)
S: 64 bits, size of the export in bytes (unsigned)
S: 32 bits, flags
S: 124 bytes, zeroes (reserved).

But buse's server sends only NBDMAGIC. How can client handshakes with the server?