Errors returned in errno:

- ESRCH (wrong read/write direction)
	- open(): _stat opened for write
	- write(): message needs to be routed to master but there is no master on the channel at the moment

- EIO (internal error)
	- _stat failed to generate content
	- impossible read() return
	- impossible write() rlist full condition

- ENXIO (chan type)
	- invalid channel type (first char of the name)

- ESPIPE (invalid slave op: master required)
	- slave open refused: channel needs to be created by master

- EEXIST (invalid master op)
 - master open refused: channel already has a master

- ENOMEM
	- failed to allocate memory (for internal/administrative purposes)

- ENODEV
	- internal error: bad channel:client address

- EFAULT
	- write(): channel needs address prefix but message is without address
	- write(): invalid address prefix