Re: [lwip-devel] Port to djgpp/Watcom

[Kieran Mansley]

On 12 Jan 2012, at 17:09, Gisle Vanem wrote:

> I've ported LwIP to djgpp (gcc 4.4.1) and OpenWatcom 1.9 on MSDOS. The main 
> hurdle was porting the packet-driver interface and sys_arch.c. Most things 
> work fine except timers are not very precise. On OpenWatcom sys_now() is 
> based on _dos_gettime() which gives only 55 msec resolution.

That resolution should be fine for lwIP.  TCP is quite tolerant of 
not-very-accurate timeouts.

> As you see the time-outs happen approx. 200 msec too late.
> What can be the reason for this? The timer granularity is 55
> ms. Would it hurt the tcp speed?

That is quite a big difference, and can't be explained by the granularity of 
your timer.  I would experiment with different TIMEOUT values and see if the 
error is proportional to the length of the timeout, or just a constant.

> If there is any interest for my DOS-port, where can I send it?
> I have no write access to git.savannah.gnu.org/cgit/lwip/lwip.git.

If you're (or someone else is) willing to maintain it so that it keeps up to 
date with the current lwIP then we can add it to the lwIP contrib git 
repository along with the other ports and give you commit access.  If you don't 
have the time to maintain it then...

> A simple .zip on my home-page?

...that would be best, and a link from the relevant page on the lwIP wiki so 
others can easily find it.

Thanks

Kieran