Re: [liblo] TCP

[Stephen S. <rad...@gm...>]

On Tue, Dec 23, 2008 at 4:46 PM, Steve Harris
<S.W...@ec...> wrote:
> On 23 Dec 2008, at 19:03, Stephen Sinclair wrote:
>
>> On Sun, Dec 21, 2008 at 3:17 AM, Kentaro Fukuchi
>> <fu...@me...> wrote:
>>> Hi Steve,
>>>
>>> It's really nice to have a keep-alive TCP connection of OSC server.
>>>
>>> On Wed, 17 Dec 2008 15:59:58 -0500
>>> "Stephen Sinclair" <rad...@gm...> wrote:
>>>
>>>> So that tells me it might be better to leave them open, so I tried
>>>> this.  It worked for a single connection, by adding a
>>>> "connected_socket" member to the lo_server structure, and polling
>>>> that
>>>> instead of the "socket" member.  However, I quickly realized that
>>>> this
>>>> would mean that lo_server would need a data structure to track _all_
>>>> open sockets.
>>>
>>> Common server programs using TCP have the same data structure to
>>> track them.
>>> For blocking server, you can use select() system call.
>>
>> Exactly, it's already using select() for Windows and poll() for *nix,
>> so it should be fairly easy to support this.  I already started
>> working on a patch but it's not ready yet.  So far I'm using a linked
>> list to keep the socket information, but I'm trying to decide if this
>> approach is more complex than necessary.
>>
>> Maybe Steve H. can tell me, but I'm not actually sure what advantage
>> poll() has over select(), actually.
>
> Not really my field, but I used to work without shouting distance of a
> load of network research people, I asked them and they said "use
> poll(), it's better" or words to that effect :)
>
> I vaguely remember that select is only efficient with a small number
> of sockets/FDs.


Hmm.. :)  Interesting, I personally haven't used poll before at all.
I looked into it, as I got curious.  It looks like select() is
basically limited in number of sockets because it uses a bitmask.

Looks like it wasn't necessary before, but if I'm to maintain a list
of sockets it works well.  I can probably save some coding by using an
array instead of a linked list and pass it in directly.  (I was trying
to avoid shuffling array items around, but now that I think about it,
it's probably a lot more efficient to shuffle an array when
connections are removed, than to build it from a list every time
lo_server_recv() is called.)

I think for portability I might change it to use autoconf to detect
poll() and use it, instead of just assuming it is there on non-Windows
systems.

Steve