brian@radio.UUCP (09/02/87)
The following is probably very simple, but darned if I can find it in the
manuals :-(
I am writing a graphics "server" on our Sun (3/180, SunOs 3.4=BSD 4.2), which
I am implementing through socket i/o. When the server is not connected I would
like to poll accept(2) periodically looking for new connections. It should be
non-blocking so that it doesn't adversely affect screen activity.
So my question is - how do I make accept non-blocking? I know it can be done.
I'm quite happy with read/write being blocking, although if they must also be
non-blocking that probably wouldn't be a hardship, although my preference
would be to leave them blocking. If it matters I'm writing the application
under the SunView windowing system.
Thanks.
--
Brian Glendenning UUCP - {allegra,decvax,pyramid}!utgpu!radio!brian
+1 (416) 978-5558 BITNET - glendenn@utorphys.bitnetchris@mimsy.UUCP (Chris Torek) (09/04/87)
In article <479@radio.toronto.edu> brian@radio.toronto.edu (Brian Glendenning) writes: >I am writing a graphics "server" on our Sun (3/180, SunOs 3.4=BSD 4.2), which >I am implementing through socket i/o. When the server is not connected I would >like to poll accept(2) periodically looking for new connections. It should be >non-blocking so that it doesn't adversely affect screen activity. > >So my question is - how do I make accept non-blocking? I know it can be done. Instead of making accept nonblocking, perform it only when it will not block. To find out when the latter is true, select the service socket (the one on which you have listen()ed) for reading: #include <sys/types.h> /* beware, 4.3BSD/V8 macros below */ fd_set rset, wset; ... if (listen(serverfd, 5)) error(...); FD_ZERO(&rset); FD_SET(serverfd, &rset); highfd = serverfd; for (;;) { fd_set r = rset, w = wset; int newfd, sourcesize; struct sockaddr_in source; nsel = select(highfd, &r, &w, (fd_set *)0, (struct timeval *)0); if (nsel <= 0) { /* if (errno == EINTR) continue; (optional) */ error(...); } if (FD_ISSET(serverfd, &r)) { sourcesize = sizeof(source); newfd = accept(servfd, &source, &sourcesize); if (newfd < 0) error(...); FD_SET(newfd, &rset); FD_SET(newfd, &wset); } ... } -- In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690) Domain: chris@mimsy.umd.edu Path: seismo!mimsy!chris
nawaf@muffy.CalComp.COM (Nawaf K. Bitar) (09/04/87)
In article <8395@mimsy.UUCP>, chris@mimsy.UUCP (Chris Torek) writes: > In article <479@radio.toronto.edu> brian@radio.toronto.edu (Brian > Glendenning) writes: > >like to poll accept(2) periodically looking for new connections. It should be > >non-blocking so that it doesn't adversely affect screen activity. > > > >So my question is - how do I make accept non-blocking? I know it can be done. > > Instead of making accept nonblocking, perform it only when it will not > block. To find out when the latter is true, select the service socket > (the one on which you have listen()ed) for reading: > > . > . > nsel = select(highfd, &r, &w, (fd_set *)0, > (struct timeval *)0); > . > . > if (FD_ISSET(serverfd, &r)) { > sourcesize = sizeof(source); > newfd = accept(servfd, &source, &sourcesize); > if (newfd < 0) > error(...); > FD_SET(newfd, &rset); > FD_SET(newfd, &wset); > } In essence what has happened here is that the select() above blocks indefinitely until some input is available. If I understand the original request you would rather poll once in a while and not block at all. I can think of three possibilities: i) Use the select() as above but supply a pointer to a zero-valued timeval struct and thus affect a poll ii) Set up the socket so that it is non-blocking; this will cause accept() to return an EWOULDBLOCK if no data is pending iii) The advanced topics section of the IPC primer blurbs something about using SIGIO with asynchronous I/O. It seems to suggest delivery of the signal on input availabilty - this might be worth investigating further. I hope this helps. -- Nawaf Bitar uucp: ...{harvard,decvax}!elrond!nawaf or nawaf@elrond.CalComp.COM usps: CalComp (A Lockheed Company), Display Products Division, Mail Stop PTP2-2D01, CS 908, Hudson NH 03051 (603) 885 8135
schung@cory.Berkeley.EDU (Stephen the Greatest) (09/04/87)
Strange..... The problem with me is that I want an accept(2) call to *block* which it doesn't. I want it to block itself when no connection is available and timeout after a while. I also want connect(2) to block and timeout. Does anyone know how to do that? - Stephen
lubich@ethz.UUCP (09/06/87)
Use ioctl (sockd, FIONBIO, 1);
It works on my uVaxII and on a Vax785 both running Ultrix 32m
--Hannes
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The usual disclaimer : No, it wasn't me, somebody must have used my account.ron@topaz.rutgers.edu (Ron Natalie) (09/06/87)
Use select to poll the socket file descriptor after doing the listen. A connection to be opened shows up as a "read" condition. This is how inetFC