Question

I’m attempting to make an iOS app communicate with a server that uses Bonjour and uses HTTP commands. So far I have been able to find the local domain and locate the particular service I’m looking for. I am able to resolve the address of the service, but I don’t know how to get something useful out of the address. The address from the NSNetService is a NSData object and I have no idea what to do with it. I need to send commands like GET and PUT. What cocoa classes handle things like this?

I also tried getting input and output streams from the Service, but they seem to be extremely low level streams and I don’t know how to properly deal with buffers and all that.

[service getInputStream:&inputStream outputStream:&outputStream]

the NSOutputStream write method takes in a uint8_t buffer which I have no idea how to create.
the NSInputStream read method returns a uint8_t buffer and I don’t know how to interpret it.

I am able to communicate with this server using terminal commands. For instance, sending it the command LIST causes it to print out the list of files I am looking for. How do I send and get information like this in Cocoa?

Answer 1

To write data to the output stream, therefore sending it to the server:

NSString * stringToSend = @"Hello World!\n"; //The "\n" lets the receiving method described below function correctly. I don't know if you need it or not.
NSData * dataToSend = [stringToSend dataUsingEncoding:NSUTF8StringEncoding];
if (outputStream) {
    int remainingToWrite = [dataToSend length];
    void * marker = (void *)[dataToSend bytes];
    while (0 < remainingToWrite) {
        int actuallyWritten = 0;
        actuallyWritten = [outputStream write:marker maxLength:remainingToWrite];
        remainingToWrite -= actuallyWritten;
        marker += actuallyWritten;
    }
}

You can send any data like this, just put it in a NSData object.

To receive data from the server use this code in the input stream’s NSStreamDelegate:

- (void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)streamEvent {
    NSInputStream * istream;
    NSOutputStream * ostream;
    switch(streamEvent) {
        case NSStreamEventHasBytesAvailable:;
            istream = (NSInputStream *)aStream;
            ostream = (NSOutputStream *)CFDictionaryGetValue(connections, istream);

            uint8_t buffer[2048];
            int actuallyRead = [istream read:(uint8_t *)buffer maxLength:2048];
            if (actuallyRead > 0) {
                NSData *data;
                data = [NSData dataWithBytes:buffer length:actuallyRead];
                NSString *string = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]autorelease];
                string = [string stringByReplacingOccurrencesOfString:@"\n" withString:@""];
                //Do something with the string...
            }
                break;
        case NSStreamEventEndEncountered:;
            istream = (NSInputStream *)aStream;
            ostream = nil;
            if (CFDictionaryGetValueIfPresent(connections, istream, (const void **)&ostream)) {
                [self shutdownInputStream:istream outputStream:ostream];
            }
                break;
        case NSStreamEventHasSpaceAvailable:
        case NSStreamEventErrorOccurred:
        case NSStreamEventOpenCompleted:
        case NSStreamEventNone:
        default:
            break;
    }
}

Take a look at Apple’s CocoaEcho Sample Code. It should help you.