> set_option serial on
-> data: serial=on

> check_tx 0x00
-> code: OK

> check_tx 0xff
-> code: OK

> append_tx 0x00
-> code: OK

> check_tx 0x00
-> code: BadNonce
-> log: Invalid nonce. Expected >= 1, got 0

> append_tx 0x01
-> code: OK

> append_tx 0x04
-> code: BadNonce
-> log: Invalid nonce. Expected 2, got 4

> info 
-> data: {"hashes":0,"txs":2}