Re: [lwip-users] Using netbufs

[Martin Velek]

Hello,

I had a similar problem. The workaround is to make  an artifical
reference to the data.
However as Simon said, be careful if you are using a DMA driver. My
case was simple - Server/Client approach with waiting for response
else retransmitt.

In the enclosure is a simple example. It is not a functional code, just snippet.

Good luck

Martin



On 17 February 2010 23:24, Joe Dupre <address@hidden> wrote:
>
> I have a simple application that sends out a UDP packet every few seconds.  
> When using the raw API, I created a raw pbuf in ram, filled the payload, and 
> then had udp_send() send that same pbuf over and over from my lwip task.
>
> Now with the Netconn API, I've created separate task to do this.  I create a 
> netbuf, fill the payload, and call netconn_sendto().  The first time the 
> packet is sent as expected, but when netconn_sendto() returns, the length of 
> my netbuf has changed, and the payload is in a different location.
>
> I see that as the netbuf's pbuf gets passed toward the interface, headers get 
> added to the payload.  But after the packet is sent the headers are not 
> removed and the netbuf I get back is no longer the netbuf that I started with.
>
> Are netbufs only designed to be used once and then thrown away?
>
> - Joe
>
>
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udpsample.txt
Description: Text document