Re: [Xenomai] need help to Xenomai Cobalt RTnet socket UDP recvfrom non blocking

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

On Fri, Jun 17, 2016 at 12:07:28PM +0200, Gilles Chanteperdrix wrote:
> On Fri, Jun 17, 2016 at 11:55:20AM +0200, Laurent LEQUIEVRE wrote:
> > Hello,
> > 
> > I installed xenomai 3.0.2 and try to test some RTnet features needed for 
> > the communication with my Kuka robot arm.
> > 
> > I specify that I want to work with the skin posix only.
> > 
> > I need to create a UDP socket with a timeout on the 'recvfrom' function 
> > (Non blocking recvfrom).
> > 
> > I tested this first code :
> > 
> > int udp_socket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
> > bind(udp_socket, ...)
> > struct timeval timeout;
> > timeout.tv_sec = 1;
> > timeout.tv_usec = 0;
> > 
> > setsockopt(udp_socket, SOL_SOCKET, SOCKET_SO_RCVTIMEO, &timeout, 
> > sizeof(timeout));
> > --> this function return -1, errno=92, Protocol not available ???
> 
> This socket option is not implemented in RTnet sockets. You can use
> the RTNET_RTIOC_TIMEOUT ioctl instead.
> 
> 
> > ....
> > recvfrom(udp_socket, ....) --> blocked ??
> > 
> > I tested this second code :
> > 
> > int udp_socket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
> > bind(udp_socket, ...)
> > fcntl(udp_socket, F_SETFL, O_NONBLOCK);
> > --> this function return 0
> > ....
> > recvfrom(udp_socket, ....) --> blocked ??
> 
> RTnet UDP recvfrom does not check the O_NONBLOCK flag, you can use
> recvmsg with MSG_DONTWAIT instead.

You can also use the MSG_DONTWAIT flag in recvfrom.

-- 
					    Gilles.
https://click-hack.org