Re: how to read one udp packet with more than one recvfrom() calls?

[Changli Gao]

On Mon, Nov 8, 2010 at 3:08 PM, ranjith kumar <ranjithproxy@xxxxxxxxx> wrote:
> Hi,
>
> I  have implemented client and server programs using udp
> protocol(files are attached).
> UDP packet size is 500bytes.
>
> I want to read these 500bytes in two calls to recvfrom(). First time
> reading 100bytes and second time 400bytes.
> How to do this?
>
> When I tried to change the third argument of recvfrom(size_t len),
> from 500 to 100, first 100bytes are read correctly.
> But when I call recvfrom() second time with len=400, it is reading the
> first 400bytes of "next udp packet".
> Why? Isn't it possible to read one udp packet in two calls to
> recvfrom()/read()????
>

recvmsg(2):

       MSG_PEEK
              This  flag  causes the receive operation to return data from the
              beginning of the receive queue without removing that  data  from
              the queue.  Thus, a subsequent receive call will return the same
              data.

-- 
Regards,
Changli Gao(xiaosuo@xxxxxxxxx)
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