Re: [lwip-users] ACK missing after SYN, strange high Ack Num

[Indan Zupancic]

On 2022-06-02 12:16, Jochen Strohbeck wrote:
> Do you know which timeout value is responsible for keeping recently
> used port numbers?

Mostly TCP_MSL. But even better would be to let the client
close the connection first.

Reducing TCP_MSL is needed if you run out of sockets or memory
and want to cleanup things quicker.

> For my testing I'm using Python requests which is doing up to 3 
> retries,
> which may cause an probably unwanted long delay in the response if
> retries are done in case the above port reuse problem occurs.

The port re-use should not add much extra delay, the RST is sent
immediately. Only if you ran out of sockets because they are all
hogged for TIME WAIT will you get extra delay.

Greetings,

Indan