# Node-red communication with NOLEK S9 via RS232

**URL:** <https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418>\
**Category:** General\
**Tags:** node-red-node-serialport\
**Created:** [7 July 2026 13:12 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418 "2026-07-07T13:12:41Z")\
**Posts on this page:** 20\
**Page:** 1

<div class="post-metadata">

**Author:** ![AlastairLong](https://avatars.discourse-cdn.com/v4/letter/a/b38774/32.png) [@AlastairLong](https://discourse.nodered.org/u/AlastairLong)\
**Post date:** [7 July 2026 13:12 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/1 "2026-07-07T13:12:41Z")

</div>

I am trying to read leak test data from a NOLEK S9 unit but i cannot appear to get this setup correctly.  
I am using a serial node with the following  
Baud rate: 9600  
Data bits: 8  
Stop bits: 2  
Parity: None  
Flow: none

Serial port : /dev/ttyS2:9600-8N2 (For COM port 1 on the IOT2040)

Node red v1.2.1 is running on a siemens IOT2040, (I know it is an older version, but the IOT2040 does not want to run anything more up to date)

Any Info on how to request data from the NOLEK unit would be greatly appreciated

---

<div class="post-metadata">

**Author:** ![ghayne](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/ghayne/32/39_2.png) [@ghayne](https://discourse.nodered.org/u/ghayne)\
**Post date:** [7 July 2026 13:58 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/2 "2026-07-07T13:58:47Z")

</div>

Welcome to the forum!

Does this show any data?

```auto
cat /dev/ttyS2:9600-8N2

```

---

<div class="post-metadata">

**Author:** ![AlastairLong](https://avatars.discourse-cdn.com/v4/letter/a/b38774/32.png) [@AlastairLong](https://discourse.nodered.org/u/AlastairLong)\
**Post date:** [7 July 2026 14:03 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/3 "2026-07-07T14:03:51Z")

</div>

Thanks for that suggestion, I get a response of No such file or directory?  
Does this mean the port is not setup correctly?

---

<div class="post-metadata">

**Author:** ![ghayne](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/ghayne/32/39_2.png) [@ghayne](https://discourse.nodered.org/u/ghayne)\
**Post date:** [7 July 2026 14:05 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/4 "2026-07-07T14:05:26Z")

</div>

try

```auto
screen /dev/ttyS2:9600-8N2

```

---

<div class="post-metadata">

**Author:** ![AlastairLong](https://avatars.discourse-cdn.com/v4/letter/a/b38774/32.png) [@AlastairLong](https://discourse.nodered.org/u/AlastairLong)\
**Post date:** [7 July 2026 14:13 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/5 "2026-07-07T14:13:44Z")

</div>

That comes back with Cannot execute, no such file or directory when I execute that query in the Terminal screen.

---

<div class="post-metadata">

**Author:** ![ghayne](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/ghayne/32/39_2.png) [@ghayne](https://discourse.nodered.org/u/ghayne)\
**Post date:** [7 July 2026 14:15 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/6 "2026-07-07T14:15:30Z")

</div>

What is the output of:

```auto
ls /dev/ttyS2*

```

---

<div class="post-metadata">

**Author:** ![AlastairLong](https://avatars.discourse-cdn.com/v4/letter/a/b38774/32.png) [@AlastairLong](https://discourse.nodered.org/u/AlastairLong)\
**Post date:** [7 July 2026 14:41 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/7 "2026-07-07T14:41:59Z")

</div>

When I type that command it responds with  
/dev/ttys2

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<div class="post-metadata">

**Author:** ![ghayne](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/ghayne/32/39_2.png) [@ghayne](https://discourse.nodered.org/u/ghayne)\
**Post date:** [7 July 2026 15:05 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/8 "2026-07-07T15:05:06Z")

</div>

Then you only need ttys2 as your port.

---

<div class="post-metadata">

**Author:** ![AlastairLong](https://avatars.discourse-cdn.com/v4/letter/a/b38774/32.png) [@AlastairLong](https://discourse.nodered.org/u/AlastairLong)\
**Post date:** [7 July 2026 15:18 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/9 "2026-07-07T15:18:20Z")

</div>

yes, I have /dev/ttyS2 as the port, see image

 ![serial port problem](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/e/b/eb8dac56ac35d616fa489bdc15b270c74bd32212.jpeg)

---

<div class="post-metadata">

**Author:** ![ghayne](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/ghayne/32/39_2.png) [@ghayne](https://discourse.nodered.org/u/ghayne)\
**Post date:** [7 July 2026 15:45 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/10 "2026-07-07T15:45:02Z")

</div>

Change ttyS2 to ttys2.

---

<div class="post-metadata">

**Author:** ![jbudd](https://avatars.discourse-cdn.com/v4/letter/j/5f8ce5/32.png) [@jbudd](https://discourse.nodered.org/u/jbudd)\
**Post date:** [7 July 2026 17:02 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/11 "2026-07-07T17:02:40Z")

</div>

> [@ghayne](#):
>
> What is the output of:
> 
> ```auto
> ls /dev/ttyS2*
> 
> ```

> [@AlastairLong](#):
>
> When I type that command it responds with  
> /dev/ttys2

I don't think those two statements make sense?  
Since bash is case sensitive, if there is a `/dev/ttys2` then `ls /dev/ttyS2*` should not show it?

---

<div class="post-metadata">

**Author:** ![ghayne](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/ghayne/32/39_2.png) [@ghayne](https://discourse.nodered.org/u/ghayne)\
**Post date:** [7 July 2026 17:10 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/12 "2026-07-07T17:10:59Z")

</div>

You are, of course, right!

---

<div class="post-metadata">

**Author:** ![marcus-j-davies](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/marcus-j-davies/32/103435_2.png) [@marcus-j-davies](https://discourse.nodered.org/u/marcus-j-davies)\
**Post date:** [7 July 2026 18:18 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/13 "2026-07-07T18:18:53Z")

</div>

is Node RED running in some type of container?  
where the physical hardware isn't present in it's virtualised env?

- Also check the credentials of the entity running Node RED, it may not have the rights to see ports (add it to the `dialout` group perhaps. -if its related of course)

I don't do (or work) on these things - but food for thought

---

<div class="post-metadata">

**Author:** ![AlastairLong](https://avatars.discourse-cdn.com/v4/letter/a/b38774/32.png) [@AlastairLong](https://discourse.nodered.org/u/AlastairLong)\
**Post date:** [8 July 2026 07:17 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/14 "2026-07-08T07:17:41Z")

</div>

There are both, i have a /dev/ttys2 and also /dev/ttyS2

I believe if i short pin 2 and 3 on the serial cable, any message sent out will be returned?  
Is that a way to check if the com port is setup correctly?

---

<div class="post-metadata">

**Author:** ![AlastairLong](https://avatars.discourse-cdn.com/v4/letter/a/b38774/32.png) [@AlastairLong](https://discourse.nodered.org/u/AlastairLong)\
**Post date:** [8 July 2026 07:39 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/15 "2026-07-08T07:39:30Z")

</div>

I shorted pin 2 and 3 and the message that was sent came back.  
Does this mean the COM port is working correctly?

---

<div class="post-metadata">

**Author:** ![Colin](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/colin/32/17040_2.png) [@Colin](https://discourse.nodered.org/u/Colin)\
**Post date:** [8 July 2026 08:13 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/16 "2026-07-08T08:13:05Z")

</div>

Yes, that is a reasonable conclusion.

---

<div class="post-metadata">

**Author:** ![jbudd](https://avatars.discourse-cdn.com/v4/letter/j/5f8ce5/32.png) [@jbudd](https://discourse.nodered.org/u/jbudd)\
**Post date:** [8 July 2026 08:52 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/17 "2026-07-08T08:52:47Z")

</div>

> [@AlastairLong](#):
>
> There are both, i have a /dev/ttys2 and also /dev/ttyS2

What does `ls -l /dev/tty[sS]2` show? Please copy the output and show us.  
This is an example from my Debian PC  
`crw-rw---- 1 root dialout 4, 66 Jun 27 15:54 /dev/ttyS2`

As I understand it, a serial port should be a character special device, so the first character of the output should be 'c'.  
Also I would expect it to have a capital S (though I don't know if the Siemens IOT2040 follows this convention).

If the /dev/ttys2 line begins with '-' then it is a normal not a character special file and was probably created in error.

---

<div class="post-metadata">

**Author:** ![AlastairLong](https://avatars.discourse-cdn.com/v4/letter/a/b38774/32.png) [@AlastairLong](https://discourse.nodered.org/u/AlastairLong)\
**Post date:** [8 July 2026 10:55 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/18 "2026-07-08T10:55:11Z")

</div>

I typed ls -l /dev/tty[sS]2 and got the following

crw-rw---- 1 root dialout 4, 66 Jul 8 11:11 /dev/ttyS2  
crw-rw-rw- 1 root tty 3, 50 Jul 7 15:08 /dev/ttys2

---

<div class="post-metadata">

**Author:** ![jbudd](https://avatars.discourse-cdn.com/v4/letter/j/5f8ce5/32.png) [@jbudd](https://discourse.nodered.org/u/jbudd)\
**Post date:** [8 July 2026 11:02 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/19 "2026-07-08T11:02:38Z")

</div>

OK thanks.

---

<div class="post-metadata">

**Author:** ![ghayne](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/ghayne/32/39_2.png) [@ghayne](https://discourse.nodered.org/u/ghayne)\
**Post date:** [8 July 2026 14:06 UTC](https://discourse.nodered.org/t/node-red-communication-with-nolek-s9-via-rs232/101418/20 "2026-07-08T14:06:45Z")

</div>

Is the node red user a member of the group dialout?

```auto
cat /etc/group | grep dialout

```

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