在后台线程中运行NSStream

Question

我目前正在尝试在后台线程中运行整个网络，因为当服务器无法访问时，它会阻塞主线程。

我目前正在通过以下代码创建网络连接。有没有简单的方法可以在新的后台线程中运行它？

我该如何将收到的消息退回主线程？一个如何通过后台线程发送消息？

CFReadStreamRef readStream;
CFWriteStreamRef writeStream;
CFStreamCreatePairWithSocketToHost(NULL, (__bridge CFStringRef)ipAdress, port, &readStream, &writeStream);
inputStream = (__bridge NSInputStream *)readStream;
outputStream = (__bridge NSOutputStream *)writeStream;
[inputStream setDelegate:self];
[outputStream setDelegate:self];
[inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];

[inputStream open];
[outputStream open];

Answer 1

这里是一个教程，完全可以满足您的要求。尽管它更多地侧重于音频流，但是原理是完全相同的（即，在生成工作线程，让它与父线程对话等方面）。

这个想法很简单..创建一个新线程并让它处理流工作，然后使用属于您刚创建的线程的运行循环来调度流读取器。该流将具有在发生某些事件（即，您获得一些数据，连接超时等）时将触发的回调。 。

这是一些代码，可以为您指明正确的方向，但是，如果您从上述教程中下载了代码，然后继续进行操作..，您将获得：

// create a new thread
internalThread =
                [[NSThread alloc]
                    initWithTarget:self
                    selector:@selector(startInternal)
                    object:nil];
            [internalThread start];

// creating a stream inside the 'startInternal' thread*
stream = CFReadStreamCreateForHTTPRequest(NULL, message);

// open stream
CFReadStreamOpen(stream) 

// set callback functions
// ie say: if there are bites available in the stream, fire a callback etc
CFStreamClientContext context = {0, self, NULL, NULL, NULL};
CFReadStreamSetClient(
        stream,
        kCFStreamEventHasBytesAvailable | kCFStreamEventErrorOccurred | kCFStreamEventEndEncountered,
        ASReadStreamCallBack,
        &context);

// schedule stream in current thread runloop, so that we DON'T block the mainthread
CFReadStreamScheduleWithRunLoop(stream, CFRunLoopGetCurrent(), kCFRunLoopCommonModes);

// create the callback function to handle reading from stream
// NOTE: see where else in the code this function is named (ie CFReadStreamSetClient)
static void ASReadStreamCallBack
(
   CFReadStreamRef aStream,
   CFStreamEventType eventType,
   void* inClientInfo
)
{
    //handle events you registered above
    // ie
    if (eventType == kCFStreamEventHasBytesAvailable) {
        // handle network data here..
        ..
        // if something goes wrong, create an alert and run it through the main thread:
        UIAlertView *alert = [
            [[UIAlertView alloc]
                initWithTitle:title
                message:message
                delegate:self
                cancelButtonTitle:NSLocalizedString(@"OK", @"")
                otherButtonTitles: nil]
            autorelease];
            [alert
                performSelector:@selector(show)
                onThread:[NSThread mainThread]
                withObject:nil
                waitUntilDone:NO];        
    }          
}