Re: [lwip-users] lwip_close() doesn't work when lwip_write() hangs

[Joel Cunningham]

It's a great trick, hopefully others can leverage it as well :)

I'm not sure what I'd do without it.  Having select() and non-blocking sockets operate as the blocking construct of a server's event loop is essential for managing multiple connections in a high performance manner.

Joel 

On Oct 12, 2015, at 02:19 PM, Sylvain Rochet <address@hidden> wrote:

Hi Joel,

On Mon, Oct 12, 2015 at 07:10:39PM +0000, Joel Cunningham wrote:

You can use SO_SNDTIMEOUT, which should work on LwIP 1.4.1. I have used it in my port with LwIP 1.4.1, so possibly there's a problem with your port?

I've also written applications that used non-blocking sockets and

select to achieve a similar behavior of having blocking I/O that can

be canceled. The trick here is adding a second socket to the read FD

set in select and then set select to block until your write or read is

ready. This second socket is bound to the loopback address. When you

want to cancel the blocking select from another thread, simply send a

datagram to the additional socket, which will return the select call.

Then you can detect that a cancel/wakeup happened because the second

socket is marked as ready.

I really like this trick. It remembers myself of the well known wake up
pipe I explained here[1], but using the loopback to do so in lwIP is
very very clever :-)

Sylvain

[1] http://lists.gnu.org/archive/html/lwip-devel/2015-09/msg00028.html

_______________________________________________
lwip-users mailing list
address@hidden
https://lists.nongnu.org/mailman/listinfo/lwip-users

signature.asc
Description: PGP signature