From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Fri, 17 Jun 2016 12:21:22 +0200
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Message-ID: <20160617102122.GL32532@hermes.click-hack.org>
References: <5763C908.6010007@gmail.com>
 <20160617100728.GK32532@hermes.click-hack.org>
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Subject: Re: [Xenomai] need help to Xenomai Cobalt RTnet socket UDP recvfrom
 non blocking
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To: Laurent LEQUIEVRE <laurent.lequievre@gmail.com>
Cc: "xenomai@xenomai.org" <xenomai@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