Lispworks Windows UDP behaviour

[Chun Tian (binghe)]

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.
> 

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