Comments on: ESP32 WebSerial: Web-based Remote Serial Monitor

By: lisztfr

lisztfr — Thu, 15 Jan 2026 08:40:19 +0000

Hi,

You forgot that the async web server cannot work together with any other web server, so for example the cam server which is using an http service… i tried this once and this won’t compile.

By: Sara Santos

Sara Santos — Mon, 29 Dec 2025 14:53:23 +0000

In reply to Hansi Walz.

Hi.
I think the author has a paid version of the library that you can use for professional use.
You can check it in the following link:
webserial.pro/?ref=ghrepo

Regards,
Sara

By: Hansi Walz

Hansi Walz — Sun, 28 Dec 2025 20:13:13 +0000

Hello Sara, hello Rui,
first I want to thank you for this tutorial, although it’s a little older it gave me many hints and ideas for my work.
Because of some problems I encountered, i tried to dive into the sources of the library and I came to some points which are partly of technical nature, but lead to an strong legal problem:
The part, which creates the web page is strongly and multiple obfuscated and minified. While the latter is not a big thing, the first does completely prevent the usage of this library for any professional work. I will explain:
The usage of the WebSerial library is licensed under the AGPL3, so any derivative work has also be licensed under AGPL3. Part of AGPL3 is that the source code has to be provided in a complete and readable form. This includes all libraries that may include. But the author has willingly decided to work against his own license by not openly distribute the original complete and readable corresponding source code.
So every creator of derivative applications are forced to do something they are not able to.
AGPL3 is a quite strong license and GNU is quite eagerly determined to enforce those rights, so I strongly recommend paying close attention and not using this library in professional projects.

By: Wizmo

Wizmo — Sat, 23 Aug 2025 17:56:02 +0000

In reply to ALi.

I went through same thing. This recipe was written a few years ago and many updates have occurred in both WebSerial and dependencies. You have a newer version of WebSerial. The old msgCallback is replaced by .onMessage. Best path forward is get the demo sketch directly from the latest WebSerial package on github e.g.
github.com/ayushsharma82/WebSerial/raw/refs/heads/master/examples/Demo/Demo.ino

Some dependencies are mentioned by previous post from Wim Deblaere, which I also discovered and eventually got both WebSerial and OTA working together.

By: ALi

ALi — Wed, 23 Jul 2025 16:32:47 +0000

Hi
I recieved error
C:\Users\user\AppData\Local\Temp.arduinoIDE-unsaved2025623-4928-1vakoit.5qob\sketch_jul23a\sketch_jul23a.ino: In function ‘void setup()’:
C:\Users\user\AppData\Local\Temp.arduinoIDE-unsaved2025623-4928-1vakoit.5qob\sketch_jul23a\sketch_jul23a.ino:50:13: error: ‘class WebSerialClass’ has no member named ‘msgCallback’
50 | WebSerial.msgCallback(&recvMsg);
| ^~~~~~~~~~~
exit status 1

Compilation error: ‘class WebSerialClass’ has no member named ‘msgCallback’
Please what is this error
i used arduino

By: Z80

Z80 — Sun, 08 Jun 2025 13:48:46 +0000

In reply to Brad Herring.

Hi Brad,
Did you figure #2 out. Ditto. Can’t seem to print in Setup(). WebSerial.println() placed after server.begin()

void setup() {
Serial.begin(115200);
pinMode(LED, OUTPUT);
WiFi.mode(WIFI_STA);
WiFi.begin(ssid, password);
if (WiFi.waitForConnectResult() != WL_CONNECTED) {
Serial.printf(“WiFi Failed!\n”);
return;
}
Serial.print(“IP Address: “);
Serial.println(WiFi.localIP());
// WebSerial is accessible at “/webserial” in browser
WebSerial.begin(&server);
WebSerial.onMessage(recvMsg);
server.begin();
WebSerial.println(“End of Setup()”);
}

By: Dana Knight

Dana Knight — Sat, 01 Mar 2025 14:43:27 +0000

In reply to Sara Santos.

Hi, I am trying to do a simple web serial solution, using no
JSON or Python or HTML, just C/C++ type solution, as if
I were debugging to a terminal session.

After trying a half dozen projects, wading thru all the lib
issues of each project, cryptic errors when I finally can
get a successful compile, a complete failure results in
Rosetta Stone type un translatable errors.

Do you know of or have a solution to this ? Or am I just
dreaming simple string data cannot be sent to web pages,
its all an illusion.

Regards, Dana.

By: Sara Santos

Sara Santos — Mon, 24 Feb 2025 02:25:29 +0000

In reply to Michael.

Hi.
You need to update to the following libraries:

https://rntlab.com/question/solvedassert-failed-tcp_alloc-idf-components-lwip-lwip-src-core-tcp-c1851-required-to-lock-tcpip-core-functionality/

I’ll update all our web server tutorials when I come back to the office.

Regards,
Sara

By: Wim Deblaere

Wim Deblaere — Sun, 23 Feb 2025 09:41:43 +0000

After some trial-and-error, I’ve found that the combination of these specific libraries versions -partially- do the job:
mathieucarbou/AsyncTCP@^3.3.2
mathieucarbou/ESPAsyncWebServer@^3.6.0
ayushsharma82/WebSerial@^2.0.8
As long as you don’t need input from the webSerial interface…
WebSerial.msgCallback(recvMsg) isn’t supported.

By: Michael

Michael — Sat, 22 Feb 2025 15:56:11 +0000

Hi.
After installing your Webserial Sketch on a ESP32, the ESP32 is booting all the time:

IP Address: 192.168.0.35

assert failed: tcp_alloc /IDF/components/lwip/lwip/src/core/tcp.c:1851 (Required to lock TCPIP core functionality!)

Backtrace: 0x40082489:0x3ffb1fe0 0x4008c321:0x3ffb2000 0x400925d6:0x3ffb2020 0x400f55d3:0x3ffb2150 0x400f574d:0x3ffb2170 0x400d580c:0x3ffb2190 0x400dd2ed:0x3ffb21e0 0x400d2a9a:0x3ffb2200 0x400e13cf:0x3ffb2270 0x4008d06a:0x3ffb2290

ELF file SHA256: 81cdc6e68

Rebooting…
ets Jul 29 2019 12:21:46

rst:0xc (SW_CPU_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0030,len:4916
load:0x40078000,len:16492
load:0x40080400,len:4
load:0x40080404,len:3524
entry 0x400805b8

What went wrong ?

rgds
Michael