NSStream 无法接收数据

Question

我正在使用连接到简单 c 套接字服务器的 NSStreams 制作聊天应用程序。流连接成功，并发送数据，但无法接收数据。这是我使用 NSStreams 的套接字类：

套接字.h

@interface Socket : NSObject <NSStreamDelegate>
- (void)connectToServerWithIP:(NSString *)ip andPort:(int)port;
- (NSString *)sendMessage:(NSString *)outgoingMessage;
@end

套接字

#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

问题是它永远挂在一行代码上：while (![inputStream hasBytesAvailable]) {}，但我不知道为什么。服务器应该发回一条消息。

Answer 1

因此，查看您的NSStreamDelegate，看起来您尚未实现该switch语句的所有情况。我最近为OS X编写了一个IRC客户端，它以非常相似的方式使用NSStream和NSStreamDelegate，我很确定当你没有检查所有的情况时，编译器应该抱怨。

回顾我的一些代码，看起来你应该检查这些情况

• NSStreamEventHasSpaceAvailable
• NSStreamEventOpenCompleted
• NSStreamEventHasBytesAvailable
• NSStreamEventEndEncountered
• NSStreamEventErrorOccurred

因此，您尚未检查的情况是 NSStreamEventHasSpaceAvailable ，这是您可以开始写入流的时候。

编辑：再次阅读您的代码，我在您的sendMessage操作中看到您正在使用outputStream对象而不是委托来编写，然后自己做工作以从inputStream中读取。我认为您可能希望使用委托，而不是直接从输入流中读取，因为它将大大简化代码从网络接收数据的方式。据我了解，NSStream是为了围绕数据从网络缓冲的事实提供一小层抽象，因此当您的输入流没有字节可供读取时，您无需执行调用usleep之类的操作。

edit2：我阅读了您关于您的代码从未通过while (![inputStream hasBytesAvailable])的更新，似乎很明显问题在于您没有正确使用流。在我看来，使用 NSStream 的最佳方式是响应事件，使用其handleEvent:(NSStreamEvent) event方法，永远不要直接告诉它写入字节，或者在它有可用字节之前休眠。

在我链接到你的代码中，我有一个readDelegate和一个writeDelegate，它们都处理NSStreams，你可能想看看我在这里如何使用我的writeDelegate。我基本上有一个方法，addCommand:(NSString *) command将一个字符串写入流到队列中，然后当我的流委托可以写入字节（NSStreamEventHasSpaceAvailable）时，我尽可能多地写入字节。我希望这有帮助！