Re: [lwip-users] UDP bind error due to address and port reuse

[Dirk Ziegelmeier]

The arguments to the function are the source IP/Port tuple of the request.

If you use udp_sendto() then the the reply packet has

• Source IP: IP of your lwIP device
• Source port: Port in your lwIP device ("x")
• Destination IP: source IP of the request = addr parameter of function
• Destination port: source port of the request = port parameter of the function

Dirk

On Tue, Dec 13, 2016 at 6:58 AM, Surya Chaitanya <address@hidden> wrote:

Hi Dirk,

I tried out the few lines of code like you suggested. It works. However, what I
don't understand is how it works, i.e., how the port parameter in the function is
the port sending the reply. Could you plz. explain. Thank You.

Regards,
Surya

On Wed, 7 Dec 2016 11:43:59 +0100, Dirk Ziegelmeier wrote
> Use one UDP PCB, bind it to IPADDR_ANY and port x.
>
> Use udp_sendto() to send to any IP/port combination.
> http://www.nongnu.org/lwip/2_0_0/group__udp__raw.html
>
> You get the src address/port of any request in your receive callback:
>
> void my_udp_recv_fn (void *arg, struct udp_pcb
> <http://www.nongnu.org/lwip/2_0_0/structudp__pcb.html> *pcb, struct pbuf
> <http://www.nongnu.org/lwip/2_0_0/structpbuf.html> *p, const ip_addr_t
>
<http://www.nongnu.org/lwip/2_0_0/group__ipaddr.html#ga44f9ada14c65d17aecf802d82eb27
3c5>
> *addr, u16_t port)
> {
>    [create new pbuf with response]
>    udp_sendto(pcb, response_pbuf, addr, port);
> [UTF-8?]​}
>
> [UTF-8?]​Dirk
> [UTF-8?]​


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