PPP does not detect modem disconnection

[vinimac]

Hi all,

I am simulating a signal loss by removing the antenna from the modem and I keep sending packets to a server using TCP socket. After remove the antenna, the function lwip_send() wont fail and error number is not set too.

I was expecting TCP layer to detect the lack of TCP ACK or PPP should have some timeout?

I am running Lwip 2.0 from ESP32 SDK .
/--------------
commit 3bf56cdd178e8b237121a8fa07862f484db68541
Merge: ba51e9fb5 d41d70b8e
Author: Angus Gratton <angus@espressif.com>
Date: Tue May 21 14:56:34 2019 +0800
/-------------

[gunar.kroeger]

We see this issue on esp-idf-v3.3 aswell.
there are a few issues opened on github regarding pppos disconnection and reconnection problems but no official answer yet /:

https://github.com/espressif/esp-idf/is ... 3Aopen+ppp

[vinimac]

PPP might detect connection loss, but TCP won't. That's expected, unless
you use LWIP_TCP_KEEPALIVE (just gxxxle for tcp keepalive...).

Regards,
Simon

http://lwip.100.n7.nabble.com/PPPos-doe ... 35008.html