Lispworks Windows UDP behaviour
Chun Tian (binghe)
binghe.lisp at gmail.com
Wed May 27 22:48:25 UTC 2015
Patch merged, thanks again!
Il giorno 27/mag/2015, alle ore 21:51, Frank James <frank.a.james at gmail.com> ha scritto:
> Great, I just had a go with your changes and it now works for me. There are a couple of typos, you don't pass in the max-buffer-size keyword arg and you forgot to rename my variable from "usocket" to "socket" (diff attached).
>
> With those changes I think I'm happy. Thanks again for looking into this for me.
> Frank,
>
>
>
> On 27 May 2015 at 19:09, Chun Tian (binghe) <binghe.lisp at gmail.com> wrote:
> Hi Frank,
>
> Thank you very much! Now I understand the issue, and I think your patch is correct. The function RECEIVE-MESSAGE was directly from my early work (the LispWorks-UDP [1] package), in which there’s no WAIT-FOR-INPUT yet, and raw socket fd is the user-level socket object. If RECEIVE-MESSAGE starts to touch the other slots in the usocket object, we should move all its code back to the SOCKET-RECEIVE method.
>
> Any way, I have committed a fix with your idea to latest Github master [2], but when I ran your test code, I get following results in both Windows and Mac:
>
> 0s 0 Waiting state NIL
> 5s 1 Waiting state NIL
> 10s 2 Waiting state NIL
> 15s 3 Waiting state NIL
>
> I think that’s because WAIT-FOR-INPUT always returns NIL (nothing can be read from the UDP server socket), therefore your other code (using SOCKET-RECEIVE and SOCKET-SEND) never get a chance to be called… do you think this is reasonable?
>
> Regards,
>
> Chun
>
> [1] https://common-lisp.net/project/cl-net-snmp/lispworks.html
> [2] https://github.com/usocket/usocket/commit/8763542e354af85989678188898af57e50fc0fbb
>
> Il giorno 26/mag/2015, alle ore 17:30, Frank James <frank.a.james at gmail.com> ha scritto:
>
> > Hi Chun,
> >
> > I've had a bit more time to look into this and I think I've got a better idea of what's going on.
> >
> > Firstly, I had a really obvious typo above (doh!) which caused the error I saw in socket-send (2, above). Putting in the count parameter and the socket-send succeeds, as expected.
> >
> > Replacing the handler-case with handler-bind and dropping into the debugger, I identified where the strange error I was seeing with socket-receive comes from (4, above). It seems the recvfrom is returning an error code of 10035, (WSAEWOULDBLOCK), which you are signalling with a condition. But the ns-try-again-condition only has a :HOST-OR-IP initarg, not a :SOCKET initarg. So I commented out that bit of code and the condition is signalled ok (although I'm not handling it, but that's fine).
> >
> > So my test function is
> >
> > (defun usocket-test ()
> > (let ((s (usocket:socket-connect nil nil
> > :protocol :datagram
> > :element-type '(unsigned-byte 8)
> > :local-port 8001)))
> > (unwind-protect
> > (do ((i 0 (1+ i))
> > (buffer (make-array 1024 :element-type '(unsigned-byte 8)
> > :initial-element 0))
> > (now (get-universal-time))
> > (done nil))
> > ((or done (= i 4))
> > nil)
> > (format t "~Ds ~D Waiting state ~S~%" (- (get-universal-time) now) i (usocket::state s))
> > (when (usocket:wait-for-input s :ready-only t :timeout 5)
> > (format t "~D state ~S~%" i (usocket::state s))
> > (handler-bind
> > ((error (lambda (c)
> > (format t "socket-receive error: ~A~%" c)
> > (break)
> > nil)))
> > (multiple-value-bind (buffer count remote-host remote-port)
> >
> > (usocket:socket-receive s buffer 1024)
> > (handler-bind
> > ((error (lambda (c)
> > (format t "socket-send error: ~A~%" c)
> > (break))))
> > (when buffer
> > (usocket:socket-send s (subseq buffer 0 count) count
> > :host remote-host
> > :port remote-port)))))))
> > (usocket:socket-close s))))
> >
> >
> >
> > My output is now:
> >
> > 0s 0 Waiting state NIL
> > 0 state :READ
> > 2s 1 Waiting state :READ
> > 1 state :READ
> > 2s 2 Waiting state :READ
> > 2 state :READ
> > 2s 3 Waiting state :READ
> > 3 state :READ
> > NIL
> >
> >
> > We are getting closer. The read state is still staying in :READ even after a successful socket-receive call, so the loop is still spinning. I can fix this easily by passing in the socket instance directly to the receive-message function and manually setting the %ready-p flag to nil. This gives me the correct behaviour:
> >
> > 0s 0 Waiting state NIL
> > 0 state :READ
> > 4s 1 Waiting state :READ
> > 9s 2 Waiting state NIL
> > 14s 3 Waiting state NIL
> > NIL
> >
> > I've attached a diff of backend/lispworks.lisp showing what I describe above, feel free to use/ignore it.
> >
> >
> > Frank.
> >
> >
> >
> > On 24 May 2015 at 20:57, Frank James <frank.a.james at gmail.com> wrote:
> > Hi Chun,
> >
> > Thanks for looking into this. I've just pulled the most recent codes from github and have had a little play with them. I now get an error signalled on the socket-receive when I expect an error (rather than a simple -1 count as before). This is good.
> >
> > However, I am still seeing the socket-state behaviour I described before, along with a new bug that has probably been introduced by the recent changes.
> >
> > Consider the following simple function which listens for UDP port 8001 for up to 4 iterations:
> >
> > (defun usocket-test ()
> > (let ((s (usocket:socket-connect nil nil
> > :protocol :datagram
> > :element-type '(unsigned-byte 8)
> > :local-port 8001)))
> > (unwind-protect
> > (do ((i 0 (1+ i))
> > (buffer (make-array 1024 :element-type '(unsigned-byte 8) :initial-element 0))
> > (done nil))
> > ((or done (= i 4))
> > nil)
> > (when (usocket:wait-for-input s :ready-only t :timeout 10)
> > (format t "~D state ~S~%" i (usocket::state s))
> > (handler-case
> > (multiple-value-bind (buffer count remote-host remote-port)
> > (usocket:socket-receive s buffer 1024)
> > (handler-case
> > (usocket:socket-send s (subseq buffer 0 count)
> > :host remote-host
> > :port remote-port)
> > (error (c)
> > (format t "socket-send error: ~A~%" c))))
> > (error (c)
> > (format t "socket-receive error: ~A~%" c)))))
> > (usocket:socket-close s))))
> >
> >
> > after calling this from your repl, from another process send a UDP packet to port 8001 to get things going. I get the following output:
> >
> > 0 state :READ
> > socket-send error: #<STANDARD-GENERIC-FUNCTION USOCKET:SOCKET-SEND 21CADCFA> is called with unpaired keyword in (2130706433 :PORT 58279).
> > 1 state :READ
> > socket-receive error: MAKE-INSTANCE is called with keyword :SOCKET among the arguments (USOCKET:NS-TRY-AGAIN-CONDITION :SOCKET 2604) which is not one of (:HOST-OR-IP).
> > 2 state :READ
> > socket-receive error: MAKE-INSTANCE is called with keyword :SOCKET among the arguments (USOCKET:NS-TRY-AGAIN-CONDITION :SOCKET 2604) which is not one of (:HOST-OR-IP).
> > 3 state :READ
> > socket-receive error: MAKE-INSTANCE is called with keyword :SOCKET among the arguments (USOCKET:NS-TRY-AGAIN-CONDITION :SOCKET 2604) which is not one of (:HOST-OR-IP).
> > NIL
> >
> > My observations:
> > 1. The initial socket-receive succeeds (as expected).
> > 2. The initial socket-send fails with an error I've not seen before and can't diagnose...
> > 3. Subsequent calls to wait-for-input return immediately because the socket is still in a :READ state, even though I already successfully called socket-receive in the first iteration.
> > 4. Subsequent calls to socket-receive now fail with a different error I can't diagnose.
> >
> > If I didn't have the max iteration cap, this would spin using 100% of a CPU core and adding around 2MB to the heap per second (on my machine), maxing out the 1GB personal edition heap limit in a short space of time. So I think it's a pretty serious issue. I mainly use SBCL, I use LispWorks occasionally to make sure my codes work on at least 1 other implementation, so I'm not exactly a LispWorks expert.
> >
> > If you want any more explanations, clarifications or examples I'll be happy to do my best to help.
> >
> > As before, I'm using LispWorks personal edition 6.1.1 on Windows 8.1.
> >
> > Frank.
> >
> >
> >
> > On 22 May 2015 at 09:24, Chun Tian (binghe) <binghe.lisp at gmail.com> wrote:
> > Hi Frank,
> >
> > Today I have modified SOCKET-SEND and SOCKET-RECEIVE for LispWorks, to be able to detect and report socket errors. I think in this way, these APIs on LispWorks could behavior closer to other platforms.
> >
> > Now on Windows, your test code should return a USOCKET:CONNECTION-RESET-ERROR condition, which equals to WSA error ECONNRESET. However, when I test the same code on Mac OS X, it instead returns USOCKET:CONNECTION-REFUSED-ERROR, I think this is a behavior of BSD sockets.
> >
> > I hope you can try latest usocket code from Git [1], to see if it works better for your case now. My code changes commit can be seen here [2].
> >
> > For wait-for-input, I can’t see what you see (the socket object remains in a :READ state), if you still think this is an issue, I hope you can create another test code to demonstrate this issue.
> >
> > Regards,
> >
> > Chun
> >
> > [1] https://github.com/usocket/usocket
> > [2] https://github.com/usocket/usocket/commit/13386639889fa812540fc4f77824c47e7616db37
> >
> > Il giorno 10/apr/2015, alle ore 23:00, Frank James <frank.a.james at gmail.com> ha scritto:
> >
> > > I've been testing some UDP codes on Lispworks (personal 32bit Windows version) and have encountered some undocumented behaviour, I think it's a matter of opinion whether it's a bug or not but it should probably have a sentence or two documenting it somewhere.
> > >
> > > Basically I'm sending a UDP packet to a host and listening for a reply, using socket-send and socket-receive. If the host in question is not listening for UDP traffic on that particular port, the Windows socket API says it should return an ECONNRESET error immediately on the socket-receive call, this is indicated by a -1 return value from the underlying recvfrom call.
> > >
> > > When this happens the Lispworks backend code returns a length of -1 (and buffer nil). This is perfectly acceptable behaviour I think (although it'd be somewhat nicer to signal an error, but that's a matter of taste). But it should be documented that checking the length here is the correct way to detect an error occurred.
> > >
> > > Example code would be something like:
> > >
> > > (let ((sock (usocket:socket-connect "localhost" 1234 :protocol :datagram :element-type '(unsigned-byte 8))))
> > > (unwind-protect
> > > (progn
> > > (usocket:socket-send sock (make-array 16 :element-type '(unsigned-byte 8) :initial-element 0) 16)
> > > (let ((buffer (make-array 16 :element-type '(unsigned-byte 8) :initial-element 0)))
> > > (usocket:socket-receive sock buffer 16)))
> > > (usocket:socket-close sock)))
> > >
> > >
> > > What is somewhat more annoying is that the socket object remains in a :READ state. This means that a polling loop using wait-for-input spins continuously, with each socket-receive returning -1 (as explained above). Probably the socket state should be cleared if a socket-receive fails.
> > >
> > > Apologies if this is all well-known to those reading this list, but it caused me 10 minutes of head scratching earlier today and thought it was worth mentioning.
> > >
> > > Frank.
> > >
> >
> >
> >
> > <diff.lisp>
>
>
> <lispworks.diff>
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