Re: [GD-General] UDP questions

[Mads B. D. <ma...@ch...>]

On Sat, 29 Jun 2002, Brian Hook wrote:

> I'm working on a basic UDP implementation right now and I'm running into 
> conflicting information on packet fragmentation.

What are your sources?

> 
> My understanding of UDP is that it's unreliable, unguaranteed, and 
> basically not going to get you data in any particular order or even at all.

Same here.

> Fine, I can deal with that.
> 
> BUT, if it DOES get you data, that data is supposed to be "complete".  In 
> other words, if Server sends a packet of 500 bytes to Client, then Client 
> will either receive that packet or none at all when it calls recv() 
> (assuming that the recv() buffer is large enough).  Yes?

That is my understanding: the fragmentation you are worrying about is on 
the IP level, ie, the UDP packet _might_ be fragmented into several IP 
packets. The IP layer should handle this, iff all packets arrive. If not, 
you loose the UDP packet.

> If I get get a positive return value from recvfrom(), can I assume that 
> it's a single complete packet?  

For UDP, yes, this is my understanding.

> Is it possible that I'll receive multiple 
> packets in a single call to recvfrom()?  Is it possible to receive a 
> partial packet?

Don't think so.

> I know that send() can deliver less than the number of bytes you request, 
> but that's easy enough to handle.

I am unsure how send() works with UDP packets. I would assume that it is 
ready to handle all valid UDP packet sizes.

Mads

-- 
Mads Bondo Dydensborg.                               ma...@ch...
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