我如何知道我的客户端 iOS 应用程序是否已连接到服务器？

Question

我按下按钮连接到服务器（TCP），但我不知道它是否连接.. 这是代码的一部分：

[self connectToServerUsingCFStream:msg portNo:50000];

    if(readStream && writeStream)
    {
        NSString *newText = [[NSString alloc] initWithFormat:@"Connected!! :)"]; 
        statusText.text = newText;
        [newText release];
        pingButton.hidden = NO;
    }
    else
    {
        NSString *newText = [[NSString alloc] initWithFormat:@"Connection unsuccessful :("]; 
        statusText.text = newText;
        [newText release];
    }

即使服务器离线，我总是得到“已连接！！:)”:s

Answer 1

对于遵循连接方法的人来说，解决方案

CFStreamCreatePairWithSocketToHost(kCFAllocatorDefault, 
                                   (CFStringRef) urlStr, 
                                   portNo, 
                                   &readStream, 
                                   &writeStream);

if (readStream && writeStream) 
{
    CFReadStreamSetProperty(readStream, 
                            kCFStreamPropertyShouldCloseNativeSocket, 
                            kCFBooleanTrue);
    CFWriteStreamSetProperty(writeStream, 
                             kCFStreamPropertyShouldCloseNativeSocket, 
                             kCFBooleanTrue);

    iStream = (NSInputStream *)readStream;
    [iStream retain];
    [iStream setDelegate:self];
    [iStream scheduleInRunLoop:[NSRunLoop currentRunLoop] 
                       forMode:NSDefaultRunLoopMode];
    [iStream open];

    oStream = (NSOutputStream *)writeStream;
    [oStream retain];
    [oStream setDelegate:self];
    [oStream scheduleInRunLoop:[NSRunLoop currentRunLoop] 
                       forMode:NSDefaultRunLoopMode];
    [oStream open];         
} 

是使用

-(void)stream:(NSStream *)theStream handleEvent:(NSStreamEvent)streamEvent ，

如下所示：（

-(void)stream:(NSStream *)theStream handleEvent:(NSStreamEvent)streamEvent
{
NSString *io;
if (theStream == iStream) io = @">>";
else io = @"<<";

NSString *event;
switch (streamEvent)
{
    case NSStreamEventNone:
        event = @"NSStreamEventNone";
        statusText.text =  @"Can not connect to the host!";
        break;

    case NSStreamEventOpenCompleted:
        event = @"NSStreamEventOpenCompleted";
        pingButton.hidden = NO;
        statusText.text = @"Connected";
        break;

    case NSStreamEventHasBytesAvailable:
        event = @"NSStreamEventHasBytesAvailable";
        if (theStream == iStream)
        {
            //read data
            uint8_t buffer[1024];
            int len;
            while ([iStream hasBytesAvailable])
            {
                len = [iStream read:buffer maxLength:sizeof(buffer)];
                if (len > 0)
                {
                    NSString *output = [[NSString alloc] initWithBytes:buffer length:len encoding:NSASCIIStringEncoding];
                    NSData *theData = [[NSData alloc] initWithBytes:buffer length:len];
                    if (nil != output)
                    {
                        //do something with data
                    }
                }
            }
        }
        break;

    case NSStreamEventHasSpaceAvailable:
        event = @"NSStreamEventHasSpaceAvailable";
        if (theStream == oStream)
        {
            //send data
            uint8_t buffer[11] = "I send this";             
            int len;

            len = [oStream write:buffer maxLength:sizeof(buffer)];
            if (len > 0)
            {
                NSLog(@"Command send");
                [oStream close];
            }
        }

        break;

    case NSStreamEventErrorOccurred:
        event = @"NSStreamEventErrorOccurred";
        statusText.text = @"Can not connect to the host!";
        pingButton.hidden = YES;
        break;

    case NSStreamEventEndEncountered:
        event = @"NSStreamEventEndEncountered";
        statusText.text = @"Connection closed by the server.";
        pingButton.hidden = YES;
        [theStream close];
        [theStream removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
        [theStream release];
        theStream = nil;
        break;

    default:
        event = @"** Unknown";
}

NSLog(@"%@ : %@", io, event);
}

据我所知！）学分转到来自这篇文章的deksa（虽然我不知道谁是创建者） ，因为我已经在网上见过几次，包括这里o SO）。这段代码被我稍微修改了（pingButton，statusText），如果您想要原始代码，请转到前面提到的链接。

Apple 开发者网站 有一些信息对此也是如此。

就像我说过的，我在网上看到过一些类似这样的东西，但现在我明白，连接后发生的一切都是“自动”的；例如，如果服务器通过read()暂停，则case NSStreamEventHasSpaceAvailable:将被自动调用，并且其中的所有代码都将运行。

现在我认为这个问题已经得到解答。

Answer 2

虽然您没有提供足够的信息，但我建议使用 ASIHTTPRequest HTTP，以及用于 TCP 和 UDP 的 AsyncSocket。如果建立了连接，就会触发回调方法，

我不得不说，我对 CFNetwork 的经验非常有限，但对我来说，好像你只是在测试流对象是否存在 (if(readStream && writeStream))。
快速浏览一下 CFNetwork 编程指南：使用读取流 告诉我，您必须使用以下命令打开它CFReadStreamOpen()，如果确实打开了流，该函数将返回一个布尔值。

if (!CFReadStreamOpen(myReadStream)) {
    CFStreamError myErr = CFReadStreamGetError(myReadStream);
    // An error has occurred.
        if (myErr.domain == kCFStreamErrorDomainPOSIX) {
        // Interpret myErr.error as a UNIX errno.
        } else if (myErr.domain == kCFStreamErrorDomainMacOSStatus) {
        // Interpret myErr.error as a MacOS error code.
            OSStatus macError = (OSStatus)myErr.error;
        // Check other error domains.
    }
}

顺便说一句：
而不是

NSString *newText = [[NSString alloc] initWithFormat:@"Connected!! :)"]; 
statusText.text = newText;
[newText release];

你可以写 statusText.text = @"Connected!! :)";