On Mar 19, 2008, at 5:58 AM, Valentin Dan wrote:
I need to send and receive message over the network but I got stuck …
Surprisingly, there is no general-purpose Cocoa wrapper for the
CFNetwork foundation functions. There are several specific wrappers -
such as NSURLConnection and NSURLDownload, but if you want to do low-
level socket communication with a protocol other than HTTP or FTP,
you're going to have to get your hands a little dirty.
You always have the option of using BSD Sockets, of course, if you
want to go old school. Or you can use the CFNetwork functions. There
are a few Objective-C wrappers provided by third parties, including
AsyncSockets, SimpleSockets, and NetSockets, but if you're going to be
doing a lot of network communication in your application, I would
recommend diving in and really learning the way CFNetwork
functionality works. Even though it's implemented with C functions
rather than Objective-C classes, it still has a lot of really nice
functionality, and since it's the basis for most (all?) of the Cocoa
networking classes, it's very robust and well-tested. It offers run
loop integration which allows you to keep from blocking without having
to detach threads . It's conceptually a little hard to wrap your head
around the way it works, but overall, it's probably your best bet
unless your needs are relatively simple, in which case something like
SimpleSockets is probably the way to go.
http://developer.apple.com/documentation/Networking/Conceptual/CFNetwork/Introduction/chapter_1_section_1.html
Here's a little trick for integrating the C callback functions into
your objective-C method. When you create your CFStreamClientContext,
pass a pointer to self in the second argument. Whatever you pass there
will get passed back to your callback function Then, in your callback
function, you can do something like this:
void readStreamCallBack(CFReadStreamRef stream, CFStreamEventType
type, void *controller)
{
id self = (id)controller;
...
If you do that, you can then makes calls against self just as you
would in one of your instance methods. The only other real gotcha is
that you have to implement a buffering scheme. The information comes
in chunks on the read stream, and on the write stream, you sometimes
have to wait and yield to the run loop before you're able to write,
and sometimes have to write in chunks. If you do not pass control back
to the run loop when the stream is not ready, it will never be ready.
Hope this helps,
Jeff
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