On Mon, 1 Sep 2003, Bert Freudenberg wrote:
> Andreas Raab wrote:
>
> > The listening socket is always bound to the local network address
> > (how could it be otherwise?)
>
> No, a socket is always bound to a network interface (how could it be
> otherwise?).
No, a socket can be bound to an object in the filesystem too.  (But I
digress... ;)
Since an interface (ignoring complications from ppp etc.) tends always
to have an assigned IP host address, the two statements are near enough
equivalent.  For a listening stream socket there is always an address
component (the port number).
The situation with dgram sockets is a little more complex, since in
addition to bind()ing the socket to a local i/f address (using
listenOnPort with a backlog of 0) you can also (reversibly) connect()
it to an address -- which will cause it to send/recv only to/from the
"connected" address.  (The VM doesn't actually do this, but it does an
equivalent thing in sqSocketConnectToPort(), which is legal for a dgram
socket, replacing the initial peer address INADDR_ANY:0 with the
specified peer address.  The use of recvfrom() and sendto() to
read/write data does the rest.  The end effect is the same.)
> Squeak does unfortunately not support this. In the plain VM, a
> listening socket is always bound to _all_ network interfaces. I
> think there have been hacks to bind to specific interfaces, but I do
> not remember where exactly I saw this.
In the VM the change needed to allow binding either a stream or a dgram
socket to an arbitrary interface address is utterly trivial (and
backwards compatible): replace the constant INADDR_ANY at line 20 of
sqListenOnPortBacklogSize() with the address of the interface to which
you want to bind.  We'd need to pass this address in as an extra
parameter, meaning a new primitive, but this isn't so bad because the
original primitive would become a one-liner (punting immediately to
the "extended" primitive, adding INADDR_ANY as the additional i/f
address argument).
Total VM support code upheaval: 2 lines modified and 3 added.
Ciao,
Ian