Re: [lwip-users] One active TCP connection at a time

[Jeffrey Nichols]

Replying to myself here. This did indeed cause issues.

Calling tcp_close() on the listening pcb inside the tcp_accept callback 
I occasionally get a deadlock inside tcp_remove_listener(), where the 
linked list is circular: pcb->next is equal to pcb.

Anyone have any ideas for how to debug/fix this?

Thanks,
Jeff

On 8/25/2019 10:28 AM, Jeffrey Nichols wrote:
> Hi,
>
> I'm trying to figure out the best way to have only one incoming TCP 
> connection active at a time.
>
> I inherited some code that calls tcp_close() on the listening pcb 
> inside the tcp_accept callback, and creates a new listener later when 
> the active connection is closed. I'm not certain that this is the best 
> way to do this, and suspect there may be edge cases that will be 
> missed. The listener has to set the SOF_REUSEADDR option whenever it 
> gets created to make everything work.
>
> I've been trying to familiarize myself with lwip and looking to see if 
> there's a supported way to achieve this functionality. Some other 
> options that occur to me are using TCP_LISTEN_BACKLOG or calling 
> tcp_abort on all of the new pcbs inside the tcp_accept callback.
>
> Does anyone have any advice for the best way to achieve only one 
> active connection at a time?
>
> Thanks,
> Jeff
>
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