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 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.

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