2010/1/13 Chun Tian (binghe) <binghe.lisp@gmail.com>
Hi, Elliott
ÔÚ 2010-1-14£¬10:02£¬ Elliott Slaughter дµÀ£º
>
> [SOCKET-SEND]
>
> Syntax: SOCKET-SEND usocket buffer length &key host port
>
> SOCKET-SEND is used for sending packets through a UDP usocket, the "buffer" arguments usually need to be a vector of (unsigned-byte 8).
>
> What does the return value of socket-send mean?
The return value of SOCKET-SEND is a integer which indicated how many bytes you actually send. In theory it should equal to the LENGTH argument in SOCKET-SEND, unless you're sending too much data. Currently the return value when sending fails is not defined clearly, for some CLs "-1" will mean "sending fail", but I think I should change it to "NIL" instead in the future.
I would probably expect usocket to throw an error if the packet failed to be sent. I would prefer that to having a special return value for failure.
The constant +max-datagram-packet-size+ is defined in usocket.lisp, line 14:
(defconstant +max-datagram-packet-size+ 65536)
I didn't export the symbol +MAX-DATAGRAM-PACKET-SIZE+ because it's a constant and hard limit of UDP implementation. Users don't need to change it's value, instead, there're extra keyword arguments in API functions when user want to set maximum packet sizes.
I'm not trying to imply that users would want to change this value, since it is a system constant, but that users might want to use it as a parameter to length in socket-receive as usocket throws an error if both buffer and length are nil. Or you might just want this to be the default (when they are both nil).
Thanks for answering my questions.
--
Elliott Slaughter
"Don't worry about what anybody else is going to do. The best way to predict the future is to invent it." - Alan Kay