ttyu vs cuau

j4ck

• Aug 7, 2013

• #1

Hi,

What is/are the difference(s) between /dev/ttyu* devices and /dev/cuau*? I can connect to a remote host via /dev/cuau2 and also /dev/ttyu2.

 

C

cpm@

Moderator

Moderator

Developer

• Aug 16, 2013

• #2

j4ck said:

What is/are the difference(s) between /dev/ttyu* devices and /dev/cuau*?

Click to expand...

The device names used for serial port devices on FreeBSD are `/dev/cua[a-z][0-9]' for dial-out devices and `/dev/tty[a-z][0-9]' for dial-in devices. Read the following related article for more information:

http://frank.harvard.edu/~coldwell/terminals/#Special%20Files.

 

aragats

• May 19, 2017

• #3

So which device node should be used when logging in a *NIX box via serial port from FreeBSD?
Both /dev/ttyX and /dev/cuaX seem to work.

 

SirDice

Administrator

Staff member

Administrator

Moderator

• May 19, 2017

• #4

From uart(4):

Code:

FILES
     /dev/ttyu?       for callin ports
     /dev/ttyu?.init
     /dev/ttyu?.lock  corresponding callin initial-state and lock-state
                      devices

     /dev/cuau?       for callout ports
     /dev/cuau?.init
     /dev/cuau?.lock  corresponding callout initial-state and lock-state
                      devices

 

aragats

• May 19, 2017

• #5

Right, thanks! But I'm a little confused since they both (ttyX and cuaX) work the same way to connect to a serial console.
So, it's seems to be more logical to use /dev/cuaX in such case, but I'm trying to understand the internals.

 

SirDice

Administrator

Staff member

Administrator

Moderator

• May 22, 2017

• #6

aragats said:

But I'm a little confused since they both (ttyX and cuaX) work the same way to connect to a serial console.

Click to expand...

Yeah, I think this is mainly because the ttyu* are the more traditional serial input ports. Think old-school, serial, terminal connections and dial-in modems.