Receiving Data from NSInputStream in Swift

Question

I try to send and receive data with NSOutputStream and NSInputStream in Swift. The sending of data is working well, but i have some questions about the receiving.

I found a solution with handling the NSStreamEvent, which i have tried.

First of all my function for initializing the connection:

func initNetworkCommunication(){  
    var host : CFString = "127.0.0.1"
    var port : UInt32 = 7001
    var readstream : Unmanaged<CFReadStream>?
    var writestream : Unmanaged<CFWriteStream>?
    CFStreamCreatePairWithSocketToHost(kCFAllocatorDefault, host, port, &readstream, &writestream)

    inputstream = readstream!.takeRetainedValue()
    outputstream = writestream!.takeRetainedValue()

    inputstream.delegate = self
    outputstream.delegate = self


    inputstream.scheduleInRunLoop(NSRunLoop.currentRunLoop(), forMode: NSDefaultRunLoopMode)
    outputstream.scheduleInRunLoop(NSRunLoop.currentRunLoop(), forMode: NSDefaultRunLoopMode)

    inputstream.open()
    outputstream.open()   
}

This part is working. I have set the delegates to self, so i should be able to handle the NSStreamEvents in this class.

func stream(aStream: NSStream, handleEvent eventCode: NSStreamEvent) {
    switch (eventCode){
    case NSStreamEvent.OpenCompleted:
        NSLog("Stream opened")
        break
    case NSStreamEvent.HasBytesAvailable:
        NSLog("HasBytesAvailable")
        break
    case NSStreamEvent.ErrorOccurred:
         NSLog("ErrorOccurred")
        break
    case NSStreamEvent.EndEncountered:
        NSLog("EndEncountered")
        break
    default:
        NSLog("unknown.")
    }
}

In my understanding everytime when some data arrives, it should print "HasBytesAvaible", but it printed "unknown." everytime. So i played around a bit and it worked with this:

func stream(aStream: NSStream, handleEvent eventCode: NSStreamEvent) {

    var buffer = [UInt8](count: 4096, repeatedValue: 0)
    while (inputstream.hasBytesAvailable){
        let result: Int = inputstream.read(&buffer, maxLength: buffer.count)
    }

    switch (eventCode){
    case NSStreamEvent.OpenCompleted:
        NSLog("Stream opened")
        break
    case NSStreamEvent.HasBytesAvailable:
        NSLog("HasBytesAvailable")
        var output = NSString(bytes: &buffer, length: buffer.count, encoding: NSUTF8StringEncoding)
        NSLog("output: %@", output)
        receiveMessage(output) //only adds the message to an array
        break
    case NSStreamEvent.ErrorOccurred:
        NSLog("ErrorOccurred")
        break
    case NSStreamEvent.EndEncountered:
          NSLog("EndEncountered")
        break
    default:
        NSLog("unknown.")
    }
}

It's working this way, but i wanted to ask you whether this is the right way ? What is the best practice at this point ?

UPDATE I worked on it again a few weeks ago and figured out my mistakes. So here is the working code.

func stream(aStream: NSStream, handleEvent eventCode: NSStreamEvent) {
        switch (eventCode){
    case NSStreamEvent.ErrorOccurred:
        NSLog("ErrorOccurred")
        break
    case NSStreamEvent.EndEncountered:
        NSLog("EndEncountered")
        break
    case NSStreamEvent.None:
        NSLog("None")
        break
    case NSStreamEvent.HasBytesAvailable:
        NSLog("HasBytesAvaible")
        var buffer = [UInt8](count: 4096, repeatedValue: 0)
        if ( aStream == inputstream){

            while (inputstream.hasBytesAvailable){
                var len = inputstream.read(&buffer, maxLength: buffer.count) 
                if(len > 0){
                    var output = NSString(bytes: &buffer, length: buffer.count, encoding: NSUTF8StringEncoding) 
                    if (output != ""){
                        NSLog("server said: %@", output!)
                    }
                }
            } 
        }
        break
    case NSStreamEvent.allZeros:
        NSLog("allZeros")
        break
    case NSStreamEvent.OpenCompleted:
        NSLog("OpenCompleted")
        break
    case NSStreamEvent.HasSpaceAvailable:
        NSLog("HasSpaceAvailable")
        break
  }

The above code is for receiving a message, not for responding to it. There are frameworks for sending and responding with sockets, maybe take a look at socket.io http://socket.io/blog/socket-io-on-ios/ — hoedding, Jan 24 '16 at 10:44
Yeah, its for receiving message but i want ask you is it going to handle if i got multiple responses from server at same time ? — Shrikant K, Jan 25 '16 at 05:39

score 3 · Accepted Answer · answered Jan 29 '15 at 12:23

3

You're missing the event hasSpaceAvailable, which I expect is occurring when it says "unknown". It's telling you that it is ready to receive more data.

Generally, I avoid using default in switch statements for enums, since the compiler will tell you when you've missed something.

answered Jan 29 '15 at 12:23

Alex

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I figured it out a few weeks ago. I will accept your answer here, because you're right. This was my mistake. – hoedding Jan 30 '15 at 13:37
Glad you sorted it – I only realised the date of your question after I'd answered! – Alex Jan 30 '15 at 13:38
@Alexander this solution will work for multiple response at a time ? in (UPDATE) – Shrikant K Jan 23 '16 at 08:01
@K.Shrikant I think you'll get better answers if you create a new question – Alex Jan 25 '16 at 13:32

score 3 · Answer 2 · answered Dec 08 '15 at 06:02

I am using the code written by hoedding, and noticed a mistake. The line:

var output = NSString(bytes: &buffer, length: buffer.count, encoding: NSUTF8StringEncoding)

should be replaced by:

var output = NSString(bytes: &buffer, length: len, encoding: NSUTF8StringEncoding)

You have to get in the output var only the number of characters returned by the server, and not the full length of the buffer, or you will get garbage from previous requests.

Receiving Data from NSInputStream in Swift

2 Answers2

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