by Chris » Wed, 22 Jan 2003 09:14:47
I have a socket that I use for read/write. When created, the socket is
blocking by default. I want it to be blocking sometimes and
non-blocking other times. I have succeeded in switching from Blocking
to Non-blocking using
fcntl(socket, F_SETFL, O_NONBLOCK);
but now I want to set it back to blocking. Is there something like
fcntl(socket, F_SETFL, O_BLOCK);
around? I cannot find a way to set it back to blocking. Thanks for any
suggestions!
-Chris
by Michael Fu » Wed, 22 Jan 2003 10:29:02
> fcntl(socket, F_SETFL, O_NONBLOCK);
Call fcntl() with F_GETFL to get the flags, then do something likeQuote:> but now I want to set it back to blocking. Is there something like
> fcntl(socket, F_SETFL, O_BLOCK);
> around? I cannot find a way to set it back to blocking. Thanks for any
> suggestions!
flags &= ~O_NONBLOCK;
Then call fcntl() with F_SETFL to set the flags.
--
Michael Fuhr
http://www.fuhr.org/~mfuhr/
by David Schwart » Wed, 22 Jan 2003 10:30:48
> Hi,
> I have a socket that I use for read/write. When created, the socket is
> blocking by default. I want it to be blocking sometimes and
> non-blocking other times. I have succeeded in switching from Blocking
> to Non-blocking using
> fcntl(socket, F_SETFL, O_NONBLOCK);
> but now I want to set it back to blocking. Is there something like
> fcntl(socket, F_SETFL, O_BLOCK);
> around? I cannot find a way to set it back to blocking. Thanks for any
> suggestions!
> -Chris
fcntl(socket, F_SETFL, 0);
should do what you want. It's good practice to do an F_GETFL to
retrieve the flags, set or clear the flags of interest, and then do an
F_SETFL with the result.
DS
1. Non blocking socket blocks; says 'read would block' ?
Hi all,
I have three sockets in server which I am reading in a continuous loop,
so don't want to wait on any one. I have designated them as 'non blocking'
but when run the server exits on the very first read() and says 'would
block'. (Is it the same as 'EWOULDBLOCK' mentioned in R. Steven's book ?)
I don't want that I should get any error msg and exit, in fact the
whole purpose of nonblocking is that if something is available, read it
else proceed in the loop and come back to read next time.
The client (sender) is sending msgs on all three sockets. The sockets
are conn_oriented. I am using SunOS 4.1. The small code part is below:
int emer_s, env_s, sens_s; /* socket fds */
//----------- making sockets nonblocking ******
if ((res=fcntl(emer_s,F_SETFL,FNDELAY)) < 0)
{
perror("fcntl res = -1");
exit(1);
}
if ((res=fcntl(env_s,F_SETFL,FNDELAY)) < 0)
{
perror("fcntl res = -1");
exit(1);
}
if ((res=fcntl(sens_s,F_SETFL,FNDELAY)) < 0)
{
perror("fcntl res = -1");
exit(1);
}
for(; ;)
{
if ((cc=read(emer_s,(char*)&gen_struct,size)) < size)
{
perror("read error");
exit(1);
}
......... do something
if ((cc=read(env_s,(char*)&gen_struct,size)) < size)
{
perror("read error");
exit(1);
}
......... do something
if ((cc=read(sens_s,(char*)&gen_struct,size)) < size)
{
perror("read error");
exit(1);
}
......... do something
}
Any help is appreciated.
hashmi
--
-----
Atiqullah Hashmi
UTA (Univ. of Texas at Arlington)
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