Re: [lwip-users] TCP behaviour with Zero Copy API using Raw API interface

[Peter Jolasson]

Hi,

I dont have a solution to your problem but I can describe a 'funny' behavior
that I've noticed with tcp_write().
When I send an even number of bytes I can set "copy" to 0.
But when sending an odd number of bytes I must set "copy" to 1 otherwise
it will fail. 

I'm using lwIP 1.1.0
//Peter

On 6/7/05, Sathya Thammanur <address@hidden> wrote:
> Hi all,
> I have a client program that connects to a server on PC. The client is
> a simple program that sends data to PC. What I notice is that when I
> call  tcp_write() with "copy" argument 1, then my program works
> without any issues. However, if I change "copy" to 0 then I notice
> that the TCP connection is not established completely. The following
> happens :
> 
> Client                            Server
> SYN ---------->
>       <---------             SYN, ACK
> 
> Junk packet sent from client. The Server resends the SYN, ACK and then
> closes the connection. TCP client sends a lost ACK with incorrect
> sequence number after couple of junk packets.
> 
> I do notice that my application call back that is registered with
> tcp_connected() is called. Here is where I start to send data. I am
> using lwip version 0.7.2.  Am I using the tcp_write() in the right way
> as intended ? Any correct usage of this function will be very useful.
> 
> Any help would be greatly appreciated.
> 
> Thanks,
> Sathya
> 
> 
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