Unable to stop

[F1p]

Requesting TelnetServer.stop(); doesn't close an active connection, only prevents new?

[Lennart Hennigs]

No, the stop() function calls WiFiServer.stop() which closes the connection:

https://github.com/arduino/esp8266/blob/1eb0645dcb82e03e239e7932ad20802c769c89e0/libraries/ESP8266WiFi/src/WiFiServer.cpp#L132

[F1p]

I observed different behaviour,

Is it possible to enable/disable the telnet server?

[Lennart Hennigs]

This is what stop()does.
You can disconnect a client via disconnectClient(bool triggerEvent = true) as stated in the documentation

[F1p]

When calling stop() I found new connections prevented, but already established connections would remain active until terminated by the user