Hi all,
I tumble on a strange behavior on using luasocket UDP sockets. It is a
borderline usage, but still I am not sure it is a bug or a feature :).
The thing happen when you want to send/receive UDP datagrams that have a size
of 0.
To produce the thing:
Into the first LuaVM:
> require 'socket'
> u=socket.udp()
> u:setsockname("*", 1025)
> =u:receivefrom()
Into the second LuaVM:
> require 'socket'
> u=socket.udp()
> =u:sendto("", "127.0.0.1", 1025)
The sendto() returns: nil, "refused"
And then the receivefrom() returns also nil, "refused"
I spied the local network, and I saw indeed 1 UDP datagram with the size equal
to 0.
So despite the errors returned, the UDP datagrams of size 0 seems to be handled
correctly by the system (Ubuntu 10.10 btw).
I looked at the source code of luasocket. In usocket.c, line 284:
int socket_recvfrom(p_socket ps, char *data, size_t count,
size_t *got,
SA *addr, socklen_t *len, p_timeout tm) {
...
long taken = (long) recvfrom(*ps, data, count, 0, addr, len);
...
if (taken == 0) return IO_CLOSED;
So a datagram of size zero is considered as a "close". Is this actually true
for a UDP socket? As it is not connected the notion of 'close' is kind of blur
to me.
There are similar thing into socket_recv, socket_send and socket_sendto
functions.
So is this a bug or a feature ?
Cuero
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