iphone - 流式获取数据 - NSInputStream

Question

全部，

我有一台服务器，它有一个用于通信的 TCP 套接字流。我需要访问该流并读取它需要发送给我的初始数据。

我目前的代码如下。老实说，我对此完全视而不见。我不确定这是否正确，更不用说适合这项工作了。

-(void) initNetworkCommunication
{
    //input stream
    NSInputStream *iStream;
    NSURL *url = [url initWithString:@"192.168.17.1:2004"];

    [iStream initWithURL:url];
    [iStream setDelegate:self];
    [iStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [iStream open];

}

所以从我的角度来看，这段代码初始化了流，但是我如何从流中读取数据呢？

谢谢

Answer 1

有两种方法可以从流中获取数据:轮询和使用流事件。

轮询更简单，但会阻塞运行它的线程。如果使用此方法，则无需执行 setDelegate: 或 scheduleInRunLoop:forMode:调用。通过重复调用 read:maxLength: 执行轮询。

NSInteger result;
uint8_t buffer[BUFFER_LEN]; // BUFFER_LEN can be any positive integer
while((result = [iStream read:buffer maxLength:BUFFER_LEN]) != 0) {
    if(result > 0) {
        // buffer contains result bytes of data to be handled
    } else {
        // The stream had an error. You can get an NSError object using [iStream streamError]
    }
}
// Either the stream ran out of data or there was an error

使用流事件需要设置委托(delegate)并将流添加到运行循环中。流不会阻塞线程，而是会在某些事件发生时(包括接收数据时)向其委托(delegate)发送一条 stream:handleEvent: 消息。然后委托(delegate)可以从流中检索数据。这是一个示例 stream:handleEvent: 方法:

- (void)stream:(NSInputStream *)iStream handleEvent:(NSStreamEvent)event {
    BOOL shouldClose = NO;
    switch(event) {
        case  NSStreamEventEndEncountered:
            shouldClose = YES;
            // If all data hasn't been read, fall through to the "has bytes" event
            if(![iStream hasBytesAvailable]) break;
        case NSStreamEventHasBytesAvailable: ; // We need a semicolon here before we can declare local variables
            uint8_t *buffer;
            NSUInteger length;
            BOOL freeBuffer = NO;
            // The stream has data. Try to get its internal buffer instead of creating one
            if(![iStream getBuffer:&buffer length:&length]) {
                // The stream couldn't provide its internal buffer. We have to make one ourselves
                buffer = malloc(BUFFER_LEN * sizeof(uint8_t));
                freeBuffer = YES;
                NSInteger result = [iStream read:buffer maxLength:BUFFER_LEN];
                if(result < 0) {
                    // error copying to buffer
                    break;
                }
                length = result;
            }
            // length bytes of data in buffer
            if(freeBuffer) free(buffer);
            break;
        case NSStreamEventErrorOccurred:
            // some other error
            shouldClose = YES;
            break;
    }
    if(shouldClose) [iStream close];
}