Errors after loading the Library

[davidlamason]

Platform

ESP32

IDE / Tooling

Arduino (IDE/CLI)

What happened?

Down load and import into Arduino as a zip lib and use the sample sketch provided and it comes up with an error

In file included from C:\Users\David.OFFICE\Documents\Arduino\WaterMeter\Webserver\Webserver.ino:2:
c:\Users\David.OFFICE\Documents\Arduino\libraries\ESP_Async_WebServer\src/ESPAsyncWebServer.h: In member function 'tcp_state AsyncWebServer::state() const':
c:\Users\David.OFFICE\Documents\Arduino\libraries\ESP_Async_WebServer\src/ESPAsyncWebServer.h:1640:49: error: passing 'const AsyncServer' as 'this' argument discards qualifiers [-fpermissive]
1640 | return static_cast<tcp_state>(_server.status());
| ~~~~~~~~~~~~~~^~
In file included from c:\Users\David.OFFICE\Documents\Arduino\libraries\ESP_Async_WebServer\src/ESPAsyncWebServer.h:38:
c:\Users\David.OFFICE\Documents\Arduino\libraries\AsyncTCP\src/AsyncTCP.h:198:13: note: in call to 'uint8_t AsyncServer::status()'
198 | uint8_t status();
| ^~~~~~
exit status 1

Compilation error: exit status 1

Stack Trace

In file included from C:\Users\David.OFFICE\AppData\Local\Temp.arduinoIDE-unsaved202633-20680-xj71yi.qwg3\ServerState\ServerState.ino:20:
c:\Users\David.OFFICE\Documents\Arduino\libraries\ESP_Async_WebServer\src/ESPAsyncWebServer.h: In member function 'tcp_state AsyncWebServer::state() const':
c:\Users\David.OFFICE\Documents\Arduino\libraries\ESP_Async_WebServer\src/ESPAsyncWebServer.h:1640:49: error: passing 'const AsyncServer' as 'this' argument discards qualifiers [-fpermissive]
1640 | return static_cast<tcp_state>(_server.status());
| ~~~~~~~~~~~~~~^~
In file included from C:\Users\David.OFFICE\AppData\Local\Temp.arduinoIDE-unsaved202633-20680-xj71yi.qwg3\ServerState\ServerState.ino:10:
c:\Users\David.OFFICE\Documents\Arduino\libraries\AsyncTCP\src/AsyncTCP.h:198:13: note: in call to 'uint8_t AsyncServer::status()'
198 | uint8_t status();
| ^~~~~~
exit status 1

Compilation error: exit status 1

Minimal Reproductible Example (MRE)

// SPDX-License-Identifier: LGPL-3.0-or-later
// Copyright 2016-2026 Hristo Gochkov, Mathieu Carbou, Emil Muratov, Will Miles

//
// Server state example
//

#include <Arduino.h>
#if defined(ESP32) || defined(LIBRETINY)
#include <AsyncTCP.h>
#include <WiFi.h>
#elif defined(ESP8266)
#include <ESP8266WiFi.h>
#include <ESPAsyncTCP.h>
#elif defined(TARGET_RP2040) || defined(TARGET_RP2350) || defined(PICO_RP2040) || defined(PICO_RP2350)
#include <RPAsyncTCP.h>
#include <WiFi.h>
#endif

#include <ESPAsyncWebServer.h>

static AsyncWebServer server1(80);
static AsyncWebServer server2(80);

void setup() {
Serial.begin(115200);

#if ASYNCWEBSERVER_WIFI_SUPPORTED
WiFi.mode(WIFI_AP);
WiFi.softAP("esp-captive");
#endif

// server state returns one of the tcp_state enum values:
// enum tcp_state {
// CLOSED = 0,
// LISTEN = 1,
// SYN_SENT = 2,
// SYN_RCVD = 3,
// ESTABLISHED = 4,
// FIN_WAIT_1 = 5,
// FIN_WAIT_2 = 6,
// CLOSE_WAIT = 7,
// CLOSING = 8,
// LAST_ACK = 9,
// TIME_WAIT = 10
// };

assert(server1.state() == tcp_state::CLOSED);
assert(server2.state() == tcp_state::CLOSED);

server1.begin();

assert(server1.state() == tcp_state::LISTEN);
assert(server2.state() == tcp_state::CLOSED);

server2.begin();

assert(server1.state() == tcp_state::LISTEN);
assert(server2.state() == tcp_state::CLOSED);

Serial.println("Done!");
}

void loop() {
delay(100);
}

I confirm that:

• I have read the documentation.
• I have searched for similar discussions.
• I have searched for similar issues.
• I have looked at the examples.
• I have upgraded to the lasted version of ESPAsyncWebServer (and AsyncTCP for ESP32).

[mathieucarbou]

@davidlamason : please open a support ticket before assuming any issue. This is not one and you would have found a solution searching in the issues or discussions of this project. I will let you give a try first before and let me know if you need more help.

[davidlamason]

Thanks for your quick reply however I must be missing something as I cant see any thing under the discussions and have spent a couple of hours searching. I have also uninstalled all other libraries and reinstalled to ensure I have the latest version of everything and including the dependent libs. Maybe you can point me to the right direction or a few links ... happy to do the research but was hoping that the example files would work straight away as I am still new to this. BTW I am using the Arduino IDE not the cloud version.

[mathieucarbou]

https://github.com/ESP32Async/ESPAsyncWebServer/discussions?discussions_q=+return+static_cast%3Ctcp_state%3E