WTH can remote serial devices not be easily mounted as /dev/tty virtual devices?

ryans · September 19, 2020, 4:04pm

Why is it cumbersome to mount remote serial devices as /dev/tty virtual devices, especially for those who aren’t as technical? Adding a native HA feature would allow EASILY using remote serial devices that are not physically connected to the same device that runs HA with any of the existing HA integrations. Basically a feature, exposed through HA UI, to use socat to mount virtual /dev/tty devices, which then ANY integration could access these remote serial devices.

This could be limited to support pseudo-terminal (pty) devices only:

the goal was to expose virtual tty devices to HA components that rely on reading/writing to local /dev/tty* for communicating with devices
for security reasons (e.g. no ability to start listeners or interact with the local filesystem on a Home Assistant instance)

Example remote serial connections:

communicating to RS232 serial devices using the IP2SL remote serial connection protocol (e.g. using IP2SL hardware devices or Virtual IP2SL)
communicating to hardware devices exposed via ser2net

Example of what configuration could look like:

remote_tty:
  - dev: marantz-stereo
    remote_address: "tcp:10.10.1.33:4999"
  - dev: pool-controller
    remote_address: "tcp:10.10.1.12:5002"
    pty_options: "waitslave"
  - dev: monoprice
    remote_address: "tcp:10.10.1.12:4999"

The remote_address option is the second address argument passed into socat.

ryans · September 19, 2020, 4:06pm

See additional threads and details on this:

123 · September 19, 2020, 4:32pm

What are the shortcomings of the Serial integration compared to your proposal?

infocus13 · September 19, 2020, 6:55pm

It looks like the serial integration relies on having a serial device (whether local or remote) at somewhere like /dev/TTYACM0.

The issue that @ryans raised means it’s not possible to get a remote device linked to a local HASS instance.

123 · September 19, 2020, 7:09pm

The Serial integration’s documentation indicates it works with ser2net and socat.

I have no practical experience with any of the above but, taking a guess, what might be the hurdle here is that (possibly) socat is not included in Home Assistant OS. That’s the version that comes with its own (restricted) hypervisor.

In contrast, Home Assistant Supervisor, Home Assistant Container, and Home Assistant Core, run on a Linux distro which typically includes socat.

EDIT

Confirmed; there’s no socat included with the hypervisor in Home Assistant OS. However it is included in the homeassistant container.

ryans · September 21, 2020, 8:06am

@infocus13 is correct! This is NOT specific to the Serial integration. The goal would be to to allow ALL integrations that rely on directly reading/writing /dev/tty* devices to be able to interact with remote serial devices. Basically, every integration that interacts over RS232/RS485/etc should be able to easily communicate with the device whether it is locally attached OR remotely attached via a common serial-over-IP protocol. socat is one way to achieve this (and probably the simplest to leverage) as it is commonly used for this.

For example, the following core integrations are impossible to use with a remote tty natively from Home Assistant, without installing socat package and hand configuring mounts:

Similarly, there are many custom components that also communicate via serial communication…ALL of these would benefit. This is especially useful for many home audio receivers/amplifiers, which often provide RS232 control, but no network accessible API.

With addition of socat and some minor UI addition (or yaml configuration), ALL integrations would be able to remotely interact with serial devices connected over IP.

darrylb · December 13, 2020, 12:08am

Did anything come from this? I’m thinking of virtualize going for redundancy after continual NUC failures and this will be a hurdle.

ryans · December 16, 2020, 6:44am

@darrylb I don’t think anyone is working on this yet, but hopefully someone picks this up and runs with it!

beerygaz · January 10, 2021, 9:33am

I am kinda gobsmacked this is not already available. I have many serial devices that are only accessible over GlobalCache or other ser2net gateways.

Given I’m new to HA I’d love to stick with the simplicity of hassos - I’m guessing right now the next best option is to build my own container stack? I’m worried about the future upgrade burden this puts on the system as I may drift further from the “supported” platform.

aceindy · January 10, 2021, 10:07am

I was under the impression that was already working, f.e. with zigbee i can choose to use serial or tcp

Just wondering how this related to this topic

ryans · March 15, 2021, 6:45am

This is not supported in HA as a generic way to mount remote serial ports (e.g. using socat or other). EACH integration has had to separately implement serial control, if they want to support it. For instance, the Zigbee integration you pointed had to manually implemented communicating via serial.

doolio · August 9, 2021, 4:54pm

I would love to see this added too and honestly with the number of Serial/RS-232 devices that are out there I’m really surprised that it hasn’t been added to HA yet. I have one old AV Matrix that is the last item in my setup that I’d like to integrate into HA but I can’t do it since I’m not a SW developer. If anyone has any updates on how to integrate Serial devices then please share

thomas-be · September 1, 2021, 10:07am

Still waiting for this feature too. It would be great to see a little more “abstraction” between HA and the hardware it is connected to. Allowing people to connect to any serial device over network seems like a basic thing to implement for home automation software.

ryans · September 1, 2021, 3:10pm

What AV matrix is that you have?

tinglis1 · September 2, 2021, 12:00am

I would like something built into HA for tcp serial. I wanted to share my workaround for a situation I have.

I have a Anthem MRX500 receiver that has rs232 only for control/monitoriong.
I have a IP-to-rs232 device (global cache iTach) connected to the receiver.
Node Red to communicate with a IP-to-rs232 device.
Send events that NR monitors and acts on.
NR monitors the tcp connection and parses the responses.
Returned data is sent as events to HA.
Automations/sensors etc in HA use the event data.

It still needs some polishing but the concept works for me and might for some of your situations.

Here is the NR flow for those who want it.

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doolio · September 2, 2021, 5:50am

Here is the solution I came up with to control my Elan S12R AV matrix switch:

I have it hooked up to a Global Cache IP2SL and using their utility iTest I realized that I could successful communicate to my S12 through my IP2SL when I was connected with Telnet.

Lightning struck and I realized that HA has a Telnet service. From there it literally took me minutes to write some code to send serial commands with the Telnet service to the IP2SL/Elan. I have it all set up and running perfectly. I even exposed it to Alexa and can now control it with voice commands.

aceindy · September 2, 2021, 11:00am

This basically means we could connect any device with JeeLabs ESPlink over ethernet, as it also support Telnet
For sure cheaper thenIP2SL

Any details on how you send serial over telnet ?

doolio · September 7, 2021, 5:30am

Here is the documentation for the Telnet service. It’s pretty straight forward. I took the serial commands for my AV Matrix and entered them in and it worked immediately (again through the Global Cache IP2SL gateway).

ryans · September 7, 2021, 7:25am

The problem is that you can’t use the Telnet service with any of the existing Home Assistant integrations that communicate RS232 over /dev/tty* local connections. That is the main issue here…just mapping Telnet into custom YAML doesn’t solve this since you have to replicate basically the entire integration.

What is needed is to be able to create a local mount point that proxies to the remote RS232 connection. Using something like iocat.

doolio · September 7, 2021, 7:33am

Yes I totally agree. This is simply a workaround and still doesn’t address all of the use cases. For example, since it’s a switch I’m not sure if I can use it to adjust the volume. Since it’s a Matrix I had to write a ton of repetitive yaml to make it work. But at least it got the AV Matrix (which was the last key integration) into HA. Something is better than nothing and I thought it could help someone else.