Re: [lwip-users] Changed IP address during runtime but TCP PCB stuck time wait state

[Ivan Warren]

Le 12/17/2018 à 4:39 AM, uaz a écrit :
> Hi All,
>
> I am doing a webserver that allows users to change device ip address during
> runtime (no power reset required).
> I've tried 2 ways of doing so:
> 1. netif_set_addr()
> 2. netif_remove() and then netif_add() a new interface with the new ip
> address
>
> In both methods, I will re-init my http server:
> 1. netconn_close()
> 2. netconn_delete()
> 3. Create a new netconn: netconn_new()
> 4. Bind to http port: netconn_bind()
>
> Unfortunately, netconn_bind() to port 80 will fail because apparently the
> previous pcb bound to port 80 is still there, in time wait state (lwip will
> not allow multiple sockets listening to the same port).
>
> How do I make sure the previous pcb is completely deleted or freed?
>
> Thanks
Apparently you need to do something like :

#define SO_REUSE to 1 in your lwipopt.h

In your application do a 
ip_set_option([yournetconn]->pcb.ip_pcb,SOF_REUSEADDR) to your new 
netconn struct before doing the netconn_bind()

This allows binding to a addr/port that is already in use by a PCB in 
TIME WAIT state.

That's what I could find looking at the source (that's not really 
documented though)

--Ivan

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