NSStream Failing To Receive Data

Question

I am making a chat application using NSStreams that connect to a simple c socket server. The stream connects successfully, and sends data, but it is unable to receive the data. Here is my Socket class that uses NSStreams:

Socket.h

@interface Socket : NSObject <NSStreamDelegate>

- (void)connectToServerWithIP:(NSString *)ip andPort:(int)port;
- (NSString *)sendMessage:(NSString *)outgoingMessage;

@end

Socket.m

#import "Socket.h"

@interface Socket ()

@property (strong, nonatomic) NSInputStream *inputStream;
@property (strong, nonatomic) NSOutputStream *outputStream;
@property (strong, nonatomic) NSString *output;

@end

@implementation Socket

@synthesize inputStream;
@synthesize outputStream;
@synthesize output;

- (void)connectToServerWithIP:(NSString *)ip andPort:(int)port
{
    CFReadStreamRef readStream;
    CFWriteStreamRef writeStream;
    CFStreamCreatePairWithSocketToHost(NULL, (__bridge CFStringRef)ip, port, &readStream, &writeStream);
    inputStream = (__bridge_transfer NSInputStream *)readStream;
    outputStream = (__bridge_transfer NSOutputStream *)writeStream;
    [inputStream setDelegate:self];
    [outputStream setDelegate:self];
    [inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [inputStream open];
    [outputStream open];
}

- (NSString *)sendMessage:(NSString *)outgoingMessage
{
    NSData *messageData = [outgoingMessage dataUsingEncoding:NSUTF8StringEncoding];
    const void *bytes = [messageData bytes];
    uint8_t *uint8_t_message = (uint8_t*)bytes;
    [outputStream write:uint8_t_message maxLength:strlen([outgoingMessage cStringUsingEncoding:[NSString defaultCStringEncoding]])];
    while (![inputStream hasBytesAvailable]) {
        usleep(10);
    }
    uint8_t buffer[1024];
    [inputStream read:buffer maxLength:1023];
    NSString *outputString = [NSString stringWithUTF8String:(char *)buffer];
    return outputString;
}

- (void)stream:(NSStream *)theStream handleEvent:(NSStreamEvent)streamEvent {
    NSLog(@"Stream Event: %lu", streamEvent);

    switch (streamEvent) {
        case NSStreamEventOpenCompleted:
            NSLog(@"Stream opened");
            break;
        case NSStreamEventHasBytesAvailable:
            if (theStream == inputStream) {
                uint8_t buffer[1024];
                long len;
                while ([inputStream hasBytesAvailable]) {
                    len = [inputStream read:buffer maxLength:sizeof(buffer)];
                    if (len > 0) {
                        output = [[NSString alloc] initWithBytes:buffer length:len encoding:NSASCIIStringEncoding];
                        if (output) {
                            NSLog(@"Data: %@", output);
                        }
                    }
                }
            }
            break;
        case NSStreamEventErrorOccurred:
            NSLog(@"Can not connect to the host!");
            break;
        case NSStreamEventEndEncountered:
            [theStream close];
            [theStream removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
            theStream = nil;
            break;
        default:
            NSLog(@"Unknown event");
    }
}

@end

ChatViewController.m

//
//  ChatViewController.m
//  Chat
//
//  Created by James Pickering on 10/5/13.
//  Copyright (c) 2013 James Pickering. All rights reserved.
//

#import "ChatViewController.h"
#import "LoginViewController.h"
#import "StatusView.h"

@interface ChatViewController ()

@property (strong) IBOutlet NSTableView *people;
@property (strong) IBOutlet NSTextField *message;
@property (strong) IBOutlet NSButton *send;
@property (strong) IBOutlet NSButton *loginButton;
@property (strong) IBOutlet NSButton *settingsButton;
@property (strong) IBOutlet NSButton *panicButton;

@property (strong, nonatomic) NSString *recievedText;
@property (strong, nonatomic) NSMutableArray *tableData;
@property (strong, nonatomic) NSInputStream *inputStream;
@property (strong, nonatomic) NSOutputStream *outputStream;


- (void)openChat:(id)sender;

- (IBAction)panic:(id)sender;
- (IBAction)loginToChat:(id)sender;

@end

@implementation ChatViewController

@synthesize sock;
@synthesize recievedText;
@synthesize inputStream;
@synthesize outputStream;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        self.isLoggedIn = FALSE;
        sock = [[Socket alloc] init];
        [sock connectToServerWithIP:@"127.0.0.1" andPort:5001];
        //[self updateUI];
    }
    return self;
}

- (void)updateUI
{
    if (self.isLoggedIn) {
        recievedText = [sock sendMessage:@"getPeople"];
        self.tableData = [[NSMutableArray alloc] initWithArray:[recievedText componentsSeparatedByString:@";"]];
        NSLog(@"%@", self.tableData);
        [self.people reloadData];
    }
}

- (void)openChat:(id)sender
{
    NSLog(@"tru");
}

- (IBAction)panic:(id)sender {

}

- (IBAction)loginToChat:(id)sender {
    NSLog(@"Called");
    if (self.loginPopover == nil) {
        NSLog(@"Login Popover is nil");
        self.loginPopover = [[NSPopover alloc] init];
        self.loginPopover.contentViewController = [[LoginViewController alloc] initWithNibName:@"LoginViewController" bundle:nil];
    }
    if (!self.loginPopover.isShown) {
        NSLog(@"Login Popover is opening");
        [self.loginButton setTitle:@"Cancel"];
        [self.settingsButton setEnabled:NO];
        [self.send setEnabled:NO];
        [self.message setEnabled:NO];
        [self.loginPopover showRelativeToRect:self.loginButton.frame ofView:self.view preferredEdge:NSMinYEdge];
    }
    else {
        NSLog(@"Login Popover is closing");
        [self.loginButton setTitle:@"Login"];
        [self.settingsButton setEnabled:YES];
        [self.send setEnabled:YES];
        [self.message setEnabled:YES];
        [self.loginPopover close];
    }
}

- (NSInteger)numberOfRowsInTableView:(NSTableView *)aTableView
{
    return [self.tableData count];
}

- (id)tableView:(NSTableView *)aTableView objectValueForTableColumn:(NSTableColumn *)aTableColumn row:(NSInteger)rowIndex
{
    return [self.tableData objectAtIndex:rowIndex];
}

- (BOOL)canBecomeKeyWindow
{
    return YES;
}

- (BOOL)loginWithUsername:(NSString *)username andPassword:(NSString *)password
{
    // Error happens here

    recievedText = [sock sendMessage:@"login"];
    if ([recievedText isEqualToString:@"roger"]) {
        recievedText = [sock sendMessage:[NSString stringWithFormat:@"%@;%@", username, password]];
        if ([recievedText isEqualToString:@"access granted"]) {
            return YES;
        }
        else {
            return NO;
        }
    }
    else {
        return NO;
    }
}

@end

The problem is that it hangs on this one line of code forever: while (![inputStream hasBytesAvailable]) {}, but I have no idea why. The server should be sending a message back.

Answer 1

So, looking at your NSStreamDelegate, it looks like you haven't implemented all of the cases for that switch statement. I recently wrote an IRC client for OS X that uses NSStream and NSStreamDelegate in a very similar way, and I'm pretty sure that the compiler should complain when you haven't checked for all of the cases there.

Looking back to some of my code it looks like you should be checking for the cases

• NSStreamEventHasSpaceAvailable
• NSStreamEventOpenCompleted
• NSStreamEventHasBytesAvailable
• NSStreamEventEndEncountered
• NSStreamEventErrorOccurred

So the case you haven't checked for is NSStreamEventHasSpaceAvailable, which is when you can start writing to your stream.

edit: Reading your code again, I see in your sendMessage action that you're using the outputStream object instead of the delegate to write, and then doing the work yourself to read from the inputStream. I think you probably want to use the delegate and never read directly from your inputstream because it will greatly simplify how your code receives data from the network. From what I understand, NSStream is there to provide a small layer of abstraction around the fact that data is buffered from the network so you don't need to do things like call usleep while your inputstream does not have bytes available to read.

edit2: I read your update about your code never getting past while (![inputStream hasBytesAvailable]) and it seems pretty clear that the problem is that you're not using your streams correctly. The way I see it, the best way to use NSStream is to respond to events, using its handleEvent:(NSStreamEvent) event method, and never directly tell it to write bytes, or to sleep until it has bytes available.

In the code I linked to you, I have a readDelegate and a writeDelegate that both handle NSStreams, you might want to take a look at how I use my writeDelegate here. I basically have a method, addCommand:(NSString *) command that puts a string to write to the stream into a queue, and then when my stream delegate can write bytes (NSStreamEventHasSpaceAvailable), I write as many bytes as I can. I hope this helps!