# atServerHelloWorld not working

**URL:** <https://forum.legato.io/t/atserverhelloworld-not-working/7004>\
**Category:** Uncategorized\
**Created:** [March 10, 2026, 5:43am UTC](https://forum.legato.io/t/atserverhelloworld-not-working/7004 "2026-03-10T05:43:36Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![ilan](https://avatars.discourse-cdn.com/v4/letter/i/ecae2f/32.png) [@ilan](https://forum.legato.io/u/ilan)\
**Post date:** [March 10, 2026, 5:43am UTC](https://forum.legato.io/t/atserverhelloworld-not-working/7004/1 "2026-03-10T05:43:36Z")

</div>

I’m trying to run the basic `atServerHelloWorld` example on a WP7607-1 running firmware R17.1 / Legato 21.05.2.

The app builds and deploys successfully. Logs confirm `AT+HELLOWORLD` is registered with `atServerDaemon`:

```auto
atServerDaemon[1260]/atServer | le_atServer.c le_atServer_Create() | Create command 'AT+HELLOWORLD'
atHelloWorldTest | atHelloWorld.c | AT+HELLOWORLD registered

```

But when I type `AT+HELLOWORLD` on `ttyUSB2` (the AT port), I get `ERROR` back immediately.

Investigation revealed that a process called `port_bridge` (started by `/etc/rcS.d/S25port_bridge`) has `at_usb0` open and bridges it directly to the modem AT parser, bypassing Legato’s `atServerDaemon` entirely:

```auto
port_bridge fd3 → /dev/at_mdm1
port_bridge fd4 → /dev/at_usb0
port_bridge fd5 → /dev/at_usb1
port_bridge fd6 → /dev/at_mdm0

```

Additionally there is a `restart_swi_app` watchdog that restarts `port_bridge` if killed.

**Questions:**

1. Is `port_bridge` supposed to be stopped before Legato’s `atService`/`portService` can own `at_usb0`?

2. What is the correct way to disable `port_bridge` permanently so `portService` takes over the USB AT port?

3. Is there a `PortConfigurationFile.json` configuration needed for `portDaemon` to open `at_usb0`?

Any guidance on the correct R17.1 setup for custom AT commands via `le_atServer` would be appreciated.

---

<div class="post-metadata">

**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/jyijyi/32/822_2.png) [@jyijyi](https://forum.legato.io/u/jyijyi)\
**Post date:** [March 10, 2026, 6:14am UTC](https://forum.legato.io/t/atserverhelloworld-not-working/7004/2 "2026-03-10T06:14:12Z")

</div>

you can see my application here:

> **[AT cmds for Mirage Talon from MangoH Red board AT port](https://mangoh.discourse.group/t/at-cmds-for-mirage-talon-from-mangoh-red-board-at-port/4803/17)**
>
> You can use my attached application as reference. Steps: enter the following AT commands in AT command port: AT!ENTERCND=“A710” AT!USBCOMP=1,1,8014D at!RESET compile and download the application in console type the following: app...

It is using USB data port for communication.