Any way to keep a TCP socket open longer than default?

[ma261065]

I have an audio player that streams audio from a server.

If the user pauses the audio, the socket stops reading data.

I understand that "unused" TCP connections will be torn down after a period of time, by design.

However, if the user then resumes the audio after the TCP keepalive expires, the socket has already closed, and I receive a socket error.

Is there any way to keep a socket alive for longer?

I see that ESP-IDF has a SO_KEEPALIVE setting, but this isn't surfaced to MicroPython:

sock.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 10000)
Traceback (most recent call last): File "<stdin>", line 1, in <module> AttributeError: 'module' object has no attribute 'SO_KEEPALIVE'

[jimmo]

It would be straightforward to add support for SO_KEEPALIVE as it's supported by LWIP (and as you note, the IDF uses LWIP, but we also use it on many other boards). See the implementation of REUSEADDR, it's much the same, just plumbing.

If you were interested in making a PR, this would need to be added to extmod/modlwip.c, ports/esp32/modsocket.c, and ports/unix/modsocket.c (and maybe Zephyr's ports/zephyr/modsocket.c too?).

(It's a bit frustrating that ESP32 has its own implementation of socket even though it's largely the same as the common LWIP one in modlwip -- it would be good to merge these one day)

[ma261065]

Thanks. I added the code to ports/esp32/modsocket.c to try it out for my use case, then called s.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1), which succeeded, but the socket still got closed after some (quite short) period of inactivity.

Do you know where the timeout is stored for closing down a socket? Is it configurable in menuconfig (I couldn't find it if it is)?