iolib-devel February 2010

iolib-devel@common-lisp.net

2 participants
6 discussions

[iolib-devel] Introductory tcp client/server examples
by Peter Keller 14 May '10

14 May '10

Hello, I've been writing a tutorial for how to use IOLib loosely following the second edition of the unix network programming book by Richard Stevens. Attached to this mail is a tarball of a collection of example programs I've written which illustrate certain concepts in using IOLib. It is intended that this tutorial go all the way from the simple iterative daytime server example, all the way to nonblocking and multiplexed network i/o for a server with many clients. I am not finished with this work at all (such as the tutorial is simply an outline and I only have a small collection of example programs!), but Stelian wanted to see examples of the code I had written and thought the list would be a good place for it. Thank you. -pete

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[iolib-devel] Patch for a nil callback invocation.
by Peter Keller 07 Mar '10

07 Mar '10

Hello, Under the conditions where there are two or more handlers registered for a single fd in the multiplexer and one of the handlers removes all the fd's callbacks and other callbacks for that fd should have been invoked in the same event-dispath iteration, there is an invocation of a nil callback in event-dispatch. To the best of my knowledge, this patch below fixes it. Thank you. -pete diff --git a/src/multiplex/event-loop.lisp b/src/multiplex/event-loop.lisp index 35879fd..4afba32 100644 --- a/src/multiplex/event-loop.lisp +++ b/src/multiplex/event-loop.lisp @@ -306,7 +306,8 @@ within the extent of BODY. Closes VAR." (setf expired-events nil) (setf (values eventsp deletion-list) (dispatch-fd-events-once event-base poll-timeout now)) - (%remove-handlers event-base deletion-list) + (unless (equal '(nil nil) deletion-list) + (%remove-handlers event-base deletion-list)) (when (expire-pending-timers fd-timers now) (setf eventsp t)) (dispatch-fd-timeouts expired-events) (when (expire-pending-timers timers now) (setf eventsp t)) @@ -352,13 +353,14 @@ within the extent of BODY. Closes VAR." (defun %dispatch-event (fd-entry event-type errorp now) (let ((ev (fd-entry-handler fd-entry event-type))) - (funcall (fd-handler-callback ev) - (fd-entry-fd fd-entry) - event-type - (if errorp :error nil)) - (when-let (timer (fd-handler-timer ev)) - (reschedule-timer-relative-to-now timer now)) - (fd-handler-one-shot-p ev))) + (when ev + (funcall (fd-handler-callback ev) + (fd-entry-fd fd-entry) + event-type + (if errorp :error nil)) + (when-let (timer (fd-handler-timer ev)) + (reschedule-timer-relative-to-now timer now)) + (fd-handler-one-shot-p ev)))) (defun dispatch-fd-timeouts (events) (dolist (ev events)

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[iolib-devel] New iolib examples, rfc
by Peter Keller 10 Feb '10

10 Feb '10

Hello, I've attached a newer version of the iolib examples I'm using for my tutorial. If people could comment upon the programs to get them more into the lisp style (except the first one or two which are C-style for a reason) or find bugs that'd be great. Thank you. -pete

1 0

[iolib-devel] with-open-socket oddness
by Peter Keller 10 Feb '10

10 Feb '10

Hello, I discovered in my boundary testing of with-open-socket that it sort of has a funny behavior I didn't expect. Basically, I had a top level code like this in a blocking i/o tcp ipv4 client talking to a server: (with-open-socket (socket :stuff :things) ;; set up i/o handlers, each wrap their reads and writes around ;; handler-case. A disconnector on the sockets removes the io handlers, but ;; doesn't close the socket since with-open-socket should do it. (handler-case ;; run forever until empty (meaning we disconnected from the server), ;; then return. (event-dispatch *base*) (hangup () (format t "Hangup while writing to server~%")) (end-of-file () (format t "End of file from server~%")))) Now, what happened was, under certain conditions where there is inflight data on the sockets, a registered handler could get a signaled condition, specifically hangup, that tells me the server went away on a write. This is expected. I disconnect the socket which removes the i/o handlers, which causes event-dispatch to return since there are no registered handlers.... and then bam! The with-open-stream performs a (finish-output) and (close) on the socket and I get _another_ hangup condition! So I had to rewrite the code like this moving the handler-case up one scope: (handler-case (with-open-socket (socket :things :stuff) ;; set up i/o handlers, each wrap their reads and writes around ;; handler-case. A disconnector on the sockets removes the io handlers, but ;; doesn't close the socket since with-open-socket should do it. (event-dispatch *base*)) (hangup () (format t "Hangup while writing to server~%")) (end-of-file () (format t "End of file from server~%")))) Is this a to be expected scenario in condition handling with respect to with-open-socket? Is this idiomatic code? Should the disconnector function close the socket even though with-open-socket also closes it? I'm not sure of the right thing to do here. Thank you. -pete

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[iolib-devel] New collection of unchecked iolib examples
by Peter Keller 01 Feb '10

01 Feb '10

Hello, In case one's curious how to use iolib, here are some unvetted examples on doing TCP/IP blocking I/O with IPV4. The program ex7-server.lisp is incomplete as of yet so ignore that one. This is for a tutorial I'm writing but which is not yet completed. I send this to the list in case I get hit by a bus or something and at least some of what I wrote makes it to the list for future people to learn from. Thank you. -pete

1 0

[iolib-devel] fd handlers
by Peter Keller 01 Feb '10

01 Feb '10

Hello, Is there a means by which a handler registered with set-io-handler can be "deactivated" so that it isn't considered in the fd set being checked and "reactivated" later to be put back into the fd set? I ask because I might not have access to the function which I want associated, say with a write handler, but when the buffer the write handler is writing is empty. If the write handler is always activated on an empty buffer solely because it is in the write handler callback, then that is a performance problem. Thank you. -pete

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iolib-devel February 2010