By Joachim Bengtsson [email protected], 2011-12-28

I like constructing simple network protocols from plist/json-safe dicts, and transmit them over the wire as json. Easy to prototype with, easy to debug. Give TCAHP an AsyncSocket, and this is what it'll do for you, plus support for request-response, and arbitrary NSData attachments.

It is an embarrassment and almost an insult that my example project is a massive 200 lines. I hope to be able to reduce the verbosity and boilerplate clutter of using TCAHP without making it heavy-weight. At the very least, I recommend that you use SPLowVerbosity.

An example of using TCAHP to send a request to update the server's MOTD:

[_proto requestHash:$dict(
    @"command", @"setMessage", // the command is 'setMessage'
    @"contents", msg // Send 'msg' as the new message to set.
) response:^(NSDictionary *response) {
    // The server has replied.
    if([[response objectForKey:@"success"] boolValue])
        NSLog(@"Successfully updated message!");
    else
        NSLog(@"Couldn't set message, because %@", [response objectForKey:@"reason"]);
}];

And on the receiving side:

-(void)request:(TCAsyncHashProtocol*)proto setMessage:(NSDictionary*)hash responder:(TCAsyncHashProtocolResponseCallback)respond;
{
    NSString *newMessage = [hash objectForKey:@"contents"];
    if([newMessage rangeOfString:@"noob"].location != NSNotFound)
        respond($dict(
            @"success", (id)kCFBooleanFalse,
            @"reason", @"you should be kind!"
        ));
    else {
        _message = newMessage;
        respond($dict(
            @"success", (id)kCFBooleanTrue
        ));
    }
}

(Note the latest piece of magic that I added, where the selector of the delegate method is created based on the value of the key 'command' in the message. I quite like it.)

As you can see, the resulting protocol is very weakly typed. In theory, this means you will be making typos and not understanding why the hell your network seems broken; in reality, I've never had that problem.