学习研究SocketRocket一

知识点：NSInputStream、 NSOutputStream 、NSStreamDelegate、 CFStreamCreatePairWithSocketToHost 、scheduleInRunLoop、 SHA1

Websocket协议原理与实现

/* From RFC:

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-------+-+-------------+-------------------------------+
 |F|R|R|R| opcode|M| Payload len |    Extended payload length    |
 |I|S|S|S|  (4)  |A|     (7)     |             (16/64)           |
 |N|V|V|V|       |S|             |   (if payload len==126/127)   |
 | |1|2|3|       |K|             |                               |
 +-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - +
 |     Extended payload length continued, if payload len == 127  |
 + - - - - - - - - - - - - - - - +-------------------------------+
 |                               |Masking-key, if MASK set to 1  |
 +-------------------------------+-------------------------------+
 | Masking-key (continued)       |          Payload Data         |
 +-------------------------------- - - - - - - - - - - - - - - - +
 :                     Payload Data continued ...                :
 + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
 |                     Payload Data continued ...                |
 +---------------------------------------------------------------+
 */
  • 在把NSData或NSString经过SHA1加密然后再转换成Base64的字符串时，一个很清晰明了的命名stringBySHA1ThenBase64Encoding,这个命名把返回值及所做的操作，先是SHA1加密，然后再转换成Base64字符串的事说的一清二楚，以后多借鉴这种简单而高效的命名方式
  • SHA即Secure Hash Algorithm（安全散列算法) 是美国国家安全局 (NSA) 设计，美国国家标准与技术研究院 (NIST) 发布的一系列密码散列函数，直接调用系统的方法
    extern unsigned char *CC_SHA1(const void *data, CC_LONG len, unsigned char *md)
    SocketRocket的实现方式如下：
static NSString *newSHA1String(const char *bytes, size_t length) {
    uint8_t md[CC_SHA1_DIGEST_LENGTH];
    assert(length >= 0);
    assert(length <= UINT32_MAX);
    CC_SHA1(bytes, (CC_LONG)length, md);
    
    NSData *data = [NSData dataWithBytes:md length:CC_SHA1_DIGEST_LENGTH];
    
    if ([data respondsToSelector:@selector(base64EncodedStringWithOptions:)]) {
        return [data base64EncodedStringWithOptions:0];
    }
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
    return [data base64Encoding];
#pragma clang diagnostic pop
}

@implementation NSData (SRWebSocket)
-(NSString *)stringBySHA1ThenBase64Encoding;
{
    return newSHA1String(self.bytes, self.length);
}
@end
@implementation NSString (SRWebSocket)
-(NSString *)stringBySHA1ThenBase64Encoding;
{
    return newSHA1String(self.UTF8String, self.length);
}
@end

创建SocketRocket的所有方法最后都调用这一个方法

- (id)initWithURLRequest:(NSURLRequest *)request protocols:(NSArray *)protocols allowsUntrustedSSLCertificates:(BOOL)allowsUntrustedSSLCertificates;
{
    self = [super init];
    if (self) {
        assert(request.URL);
        _url = request.URL;
        _urlRequest = request;
        _allowsUntrustedSSLCertificates = allowsUntrustedSSLCertificates;
        
        _requestedProtocols = [protocols copy];
        
        [self _SR_commonInit];
    }
    
    return self;
}

这个共通初始化调用方法判断url的scheme，只支持ws、wss、http、https，如果是wss、https就是安全请求

- (void)_SR_commonInit;
{
    NSString *scheme = _url.scheme.lowercaseString;
    assert([scheme isEqualToString:@"ws"] || [scheme isEqualToString:@"http"] || [scheme isEqualToString:@"wss"] || [scheme isEqualToString:@"https"]);
    
    if ([scheme isEqualToString:@"wss"] || [scheme isEqualToString:@"https"]) {
        _secure = YES;
    }
    
    _readyState = SR_CONNECTING;
    _consumerStopped = YES;
    _webSocketVersion = 13;
    
    _workQueue = dispatch_queue_create(NULL, DISPATCH_QUEUE_SERIAL);
    
    // Going to set a specific on the queue so we can validate we're on the work queue
    dispatch_queue_set_specific(_workQueue, (__bridge void *)self, maybe_bridge(_workQueue), NULL);
    
    _delegateDispatchQueue = dispatch_get_main_queue();
    sr_dispatch_retain(_delegateDispatchQueue);
    
    _readBuffer = [[NSMutableData alloc] init];
    _outputBuffer = [[NSMutableData alloc] init];
    
    _currentFrameData = [[NSMutableData alloc] init];

    _consumers = [[NSMutableArray alloc] init];
    
    _consumerPool = [[SRIOConsumerPool alloc] init];
    
    _scheduledRunloops = [[NSMutableSet alloc] init];
    
    [self _initializeStreams];
    
    // default handlers
}
  • 如果没有设置端口，则设置默认的80或安全请求的443端口
  • 使用CFStreamCreatePairWithSocketToHost创建socket连接
    同时创建NSInputStream及NSOutputStream
- (void)_initializeStreams;
{
    assert(_url.port.unsignedIntValue <= UINT32_MAX);
    uint32_t port = _url.port.unsignedIntValue;
    if (port == 0) {
        if (!_secure) {
            port = 80;
        } else {
            port = 443;
        }
    }
    NSString *host = _url.host;
    
    CFReadStreamRef readStream = NULL;
    CFWriteStreamRef writeStream = NULL;
    
    CFStreamCreatePairWithSocketToHost(NULL, (__bridge CFStringRef)host, port, &readStream, &writeStream);
    
    _outputStream = CFBridgingRelease(writeStream);
    _inputStream = CFBridgingRelease(readStream);
    
    _inputStream.delegate = self;
    _outputStream.delegate = self;
}
  • 开启连接,在超时时间后状态还是链接中，则说明链接超时，执行出错提示
  • 对安全链接进行设置
  • 如果没有设置过outputStream和inputStream的的runloop，设置默认的runloop
-(void)open;
{
    assert(_url);
    NSAssert(_readyState == SR_CONNECTING, @"Cannot call -(void)open on SRWebSocket more than once");

    _selfRetain = self;

    if (_urlRequest.timeoutInterval > 0)
    {
        dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, _urlRequest.timeoutInterval * NSEC_PER_SEC);
        dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
            if (self.readyState == SR_CONNECTING)
                [self _failWithError:[NSError errorWithDomain:@"com.squareup.SocketRocket" code:504 userInfo:@{NSLocalizedDescriptionKey: @"Timeout Connecting to Server"}]];
        });
    }

    [self openConnection];
}
- (void)openConnection;
{
    [self _updateSecureStreamOptions];
    
    if (!_scheduledRunloops.count) {
        [self scheduleInRunLoop:[NSRunLoop SR_networkRunLoop] forMode:NSDefaultRunLoopMode];
    }
    
    
    [_outputStream open];
    [_inputStream open];
}
#pragma mark 设置NSStream工作所在的runloop及mode
- (void)scheduleInRunLoop:(NSRunLoop *)aRunLoop forMode:(NSString *)mode;
{
    [_outputStream scheduleInRunLoop:aRunLoop forMode:mode];
    [_inputStream scheduleInRunLoop:aRunLoop forMode:mode];
    
    [_scheduledRunloops addObject:@[aRunLoop, mode]];
}

- (void)unscheduleFromRunLoop:(NSRunLoop *)aRunLoop forMode:(NSString *)mode;
{
    [_outputStream removeFromRunLoop:aRunLoop forMode:mode];
    [_inputStream removeFromRunLoop:aRunLoop forMode:mode];
    
    [_scheduledRunloops removeObject:@[aRunLoop, mode]];
}
  • 发送数据
  • 发送的连接数据时放在初始化的request中，以后发送心跳包的ping是使用send方法
-(void)send:(id)data;
{
    NSAssert(self.readyState != SR_CONNECTING, @"Invalid State: Cannot call send: until connection is open");
    // TODO: maybe not copy this for performance
    data = [data copy];
    dispatch_async(_workQueue, ^{
        if ([data isKindOfClass:[NSString class]]) {
            [self _sendFrameWithOpcode:SROpCodeTextFrame data:[(NSString *)data dataUsingEncoding:NSUTF8StringEncoding]];
        } else if ([data isKindOfClass:[NSData class]]) {
            [self _sendFrameWithOpcode:SROpCodeBinaryFrame data:data];
        } else if (data == nil) {
            [self _sendFrameWithOpcode:SROpCodeTextFrame data:data];
        } else {
            assert(NO);
        }
    });
}

将数据封装成socket的协议数据

static const size_t SRFrameHeaderOverhead = 32;
-(void)_sendFrameWithOpcode:(SROpCode)opcode data:(id)data;
{
    [self assertOnWorkQueue];
    
    if (nil == data) {
        return;
    }
    
    NSAssert([data isKindOfClass:[NSData class]] || [data isKindOfClass:[NSString class]], @"NSString or NSData");
    
    size_t payloadLength = [data isKindOfClass:[NSString class]] ? [(NSString *)data lengthOfBytesUsingEncoding:NSUTF8StringEncoding] : [data length];
        
    NSMutableData *frame = [[NSMutableData alloc] initWithLength:payloadLength + SRFrameHeaderOverhead];
    if (!frame) {
        [self closeWithCode:SRStatusCodeMessageTooBig reason:@"Message too big"];
        return;
    }
    uint8_t *frame_buffer = (uint8_t *)[frame mutableBytes];
    
    // set fin
    frame_buffer[0] = SRFinMask | opcode;
    
    BOOL useMask = YES;
#ifdef NOMASK
    useMask = NO;
#endif
    
    if (useMask) {
    // set the mask and header
        frame_buffer[1] |= SRMaskMask;
    }
    
    size_t frame_buffer_size = 2;
    
    const uint8_t *unmasked_payload = NULL;
    if ([data isKindOfClass:[NSData class]]) {
        unmasked_payload = (uint8_t *)[data bytes];
    } else if ([data isKindOfClass:[NSString class]]) {
        unmasked_payload =  (const uint8_t *)[data UTF8String];
    } else {
        return;
    }
    
    if (payloadLength < 126) {
        frame_buffer[1] |= payloadLength;
    } else if (payloadLength <= UINT16_MAX) {
        frame_buffer[1] |= 126;
        *((uint16_t *)(frame_buffer + frame_buffer_size)) = EndianU16_BtoN((uint16_t)payloadLength);
        frame_buffer_size += sizeof(uint16_t);
    } else {
        frame_buffer[1] |= 127;
        *((uint64_t *)(frame_buffer + frame_buffer_size)) = EndianU64_BtoN((uint64_t)payloadLength);
        frame_buffer_size += sizeof(uint64_t);
    }
        
    if (!useMask) {
        for (size_t i = 0; i < payloadLength; i++) {
            frame_buffer[frame_buffer_size] = unmasked_payload[i];
            frame_buffer_size += 1;
        }
    } else {
        uint8_t *mask_key = frame_buffer + frame_buffer_size;
        SecRandomCopyBytes(kSecRandomDefault, sizeof(uint32_t), (uint8_t *)mask_key);
        frame_buffer_size += sizeof(uint32_t);
        
        // TODO: could probably optimize this with SIMD
        for (size_t i = 0; i < payloadLength; i++) {
            frame_buffer[frame_buffer_size] = unmasked_payload[i] ^ mask_key[i % sizeof(uint32_t)];
            frame_buffer_size += 1;
        }
    }

    assert(frame_buffer_size <= [frame length]);
    frame.length = frame_buffer_size;
    
    [self _writeData:frame];
}
  • 发送数据
  • 忘后台发送数据总共有4个地方，
    1、是发送一般数据或心跳包
    2、调用close时也是给后台发送数据
    3、4都是在Input/outputStream的代理回调时
    - (void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode
    - (void)safeHandleEvent:(NSStreamEvent)eventCode stream:(NSStream *)aStream NSStreamEventOpenCompleted/NSStreamEventHasSpaceAvailable
-(void)_writeData:(NSData *)data;
{    
    [self assertOnWorkQueue];

    if (_closeWhenFinishedWriting) {
            return;
    }
    [_outputBuffer appendData:data];
    [self _pumpWriting];
}
-(void)_pumpWriting;
{
    [self assertOnWorkQueue];
    
    NSUInteger dataLength = _outputBuffer.length;
    if (dataLength - _outputBufferOffset > 0 && _outputStream.hasSpaceAvailable) {
        NSInteger bytesWritten = [_outputStream write:_outputBuffer.bytes + _outputBufferOffset maxLength:dataLength - _outputBufferOffset];
        if (bytesWritten == -1) {
            [self _failWithError:[NSError errorWithDomain:SRWebSocketErrorDomain code:2145 userInfo:[NSDictionary dictionaryWithObject:@"Error writing to stream" forKey:NSLocalizedDescriptionKey]]];
             return;
        }        
        _outputBufferOffset += bytesWritten;
        if (_outputBufferOffset > 4096 && _outputBufferOffset > (_outputBuffer.length >> 1)) {
            _outputBuffer = [[NSMutableData alloc] initWithBytes:(char *)_outputBuffer.bytes + _outputBufferOffset length:_outputBuffer.length - _outputBufferOffset];
            _outputBufferOffset = 0;
        } }   if (_closeWhenFinishedWriting && 
        _outputBuffer.length - _outputBufferOffset == 0 && 
        (_inputStream.streamStatus != NSStreamStatusNotOpen &&
         _inputStream.streamStatus != NSStreamStatusClosed) &&
        !_sentClose) {
        _sentClose = YES;
        
        @synchronized(self) {
            [_outputStream close];
            [_inputStream close];
             for (NSArray *runLoop in [_scheduledRunloops copy]) {
                [self unscheduleFromRunLoop:[runLoop objectAtIndex:0] forMode:[runLoop objectAtIndex:1]];
            }
        }
        
        if (!_failed) {
            [self _performDelegateBlock:^{
                if ([self.delegate respondsToSelector:@selector(webSocket:didCloseWithCode:reason:wasClean:)]) {
                    [self.delegate webSocket:self didCloseWithCode:_closeCode reason:_closeReason wasClean:YES];
                }
            }];
        } [self _scheduleCleanup];  } }
  • 清空数据
-(void)_scheduleCleanup { 
@synchronized(self) {
        if (_cleanupScheduled) {
            return; }
        _cleanupScheduled = YES;        
        // Cleanup NSStream delegate's in the same RunLoop used by the streams themselves:
        // This way we'll prevent race conditions between handleEvent and SRWebsocket's dealloc
        NSTimer *timer = [NSTimer timerWithTimeInterval:(0.0f) target:self selector:@selector(_cleanupSelfReference:) userInfo:nil repeats:NO];
        [[NSRunLoop SR_networkRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];}
}
-(void)_cleanupSelfReference:(NSTimer *)timer
{
    @synchronized(self) {
        // Nuke NSStream delegate's
        _inputStream.delegate = nil;
        _outputStream.delegate = nil;
        
        // Remove the streams, right now, from the networkRunLoop
        [_inputStream close];
        [_outputStream close];
    }
    
    // Cleanup selfRetain in the same GCD queue as usual
    dispatch_async(_workQueue, ^{
        _selfRetain = nil;
    });
}
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