Iphone listen a tcp port

Question

I read some suggested links from the other answers to similar questions. Article1, Library1, Another SO Question. However, I couldn't figure out how to do the following application.

Basically, I send to Iphone's IP and a chosen port (let's say port: 2020) a string. And I want to show this string on the Iphone's UI. So, let's check the following example code:

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    NSString* str;
    while(true)
    {
         str = ReadLineFromPort(2020);
         myLabel.text = str;
    }
}

I expect the ReadLineFromPort() method to have the following duty:

Read until you see a line break (i.e., '\n') and when you see the line break return the string. (Similar to the C# StreamReader.Readline method.)

Any help will be greatly appreciated. Since I'm not a pro IOS developer I need a basic one though.

Answer 1

Listening to some TCP port does require some things to set up.

A good choice would be to use Robbie Hanson's CocoaAsyncSocket.

There you'll find an example for Echo Server (in RunLoop/XCode/EchoServer.

True, this XCode project was generated for OSX but you can simply create an empty iOS project and copy-paste most of the code.

There is no 'read until break' functionality though - but it is simple enough to implement while copying data to receive buffer.

EDIT:

You'd typically want to modify onSocket: didReadData: withTag:

- (void)onSocket:(AsyncSocket *)sock didReadData:(NSData *)data withTag:(long)tag
{
    NSData *strData = [data subdataWithRange:NSMakeRange(0, [data length])];
    NSString *str = [[NSString alloc] initWithData:strData encoding:NSUTF8StringEncoding];
    if(str)
    {
      myLabel.text = str;   
    }
}

Now, this code does not detect \n in incoming data. You could for example define an ivar or property rx_buffer

NSMutableString *rx_buffer;

which would be built with

rx_buffer = [rx_buffer stringByAppendingString: str];

until you detect \n in str.