网络架构

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CFNetwork：依赖于Core Foundation框架的两个API，CFSocket和CFStream。

CFSocket：主要用于网络底层的通信，套接字是网络通信最基本的层级。一个套接字的作用类似与打电话的方式。它允许你连接到另一个套接字（无论本地或者通过网络）并将数据发送到该套接字。

CFStream：包括CFReadStream 和 CFWriteStream，分别用于对Socket的读取和写入。

CFHTTP：去发送和接收HTTP消息，使用CFHTTP API。

HTTP请求实现过程

1.使用CFHTTP的接口创建HTTP请求
2.使用CFStream的接口序列化和发送CFHTTP请求并接收响应
3.把响应转换为对应的格式（JSON）

//创建请求
    CFStringRef url = CFSTR("https://app.*******.com/admin/index/start");
    CFURLRef myURL = CFURLCreateWithString(kCFAllocatorDefault, url, NULL);
    
    CFStringRef requestMethod = CFSTR("POST");
    CFHTTPMessageRef myRequest =
    CFHTTPMessageCreateRequest(kCFAllocatorDefault, requestMethod, myURL,
                               kCFHTTPVersion1_1);
// 设置body
    NSData *dataToPost = [@"apptoken=-1" dataUsingEncoding:NSUTF8StringEncoding];
    CFHTTPMessageSetBody(myRequest, (__bridge CFDataRef) dataToPost);
// 设置header
CFHTTPMessageSetHeaderFieldValue(myRequest, CFSTR("Content-Type"), CFSTR("application/x-www-form-urlencoded; charset=utf-8"));

//创建流并开启
    CFReadStreamRef requestStream = CFReadStreamCreateForHTTPRequest(NULL, myRequest);
    CFReadStreamOpen(requestStream);
    //接收响应
    NSMutableData *responseBytes = [NSMutableData data];
    CFIndex numBytesRead = 0;
    do {
        UInt8 buf[1024];
        numBytesRead = CFReadStreamRead(requestStream, buf, sizeof(buf));
        
        if (numBytesRead > 0) {
            [responseBytes appendBytes:buf length:numBytesRead];
        }
    } while (numBytesRead > 0);
    
    CFHTTPMessageRef response = (CFHTTPMessageRef) CFReadStreamCopyProperty(requestStream, kCFStreamPropertyHTTPResponseHeader);
    CFHTTPMessageSetBody(response, (__bridge CFDataRef)responseBytes);
    CFReadStreamClose(requestStream);
    CFRelease(requestStream);
    CFAutorelease(response);

//转换为JSON
    CFIndex statusCode;
    statusCode = CFHTTPMessageGetResponseStatusCode(response);
    CFDataRef responseDataRef = CFHTTPMessageCopyBody(response);
    NSData *responseData = (__bridge NSData *)responseDataRef;
    NSMutableDictionary *jsonInfo = [responseData JSONValue];

    NSLog(@"responseBody: %@", jsonInfo);