ios16.3.1创建TCP长连接

在 iOS 13 之前，可以使用 `CFStream` 和 `CFNetwork` 库来创建 TCP 长连接。以下是一个简单的示例：

CFReadStreamRef readStream;
CFWriteStreamRef writeStream;
CFStreamCreatePairWithSocketToHost(NULL, (__bridge CFStringRef)@"example.com", 80, &readStream, &writeStream);

CFReadStreamOpen(readStream);
CFWriteStreamOpen(writeStream);

// 写入数据
NSString *requestStr = @"GET / HTTP/1.0\r\n\r\n";
NSData *requestData = [requestStr dataUsingEncoding:NSUTF8StringEncoding];
CFIndex bytesWritten = CFWriteStreamWrite(writeStream, [requestData bytes], [requestData length]);
NSLog(@"%ld bytes written", bytesWritten);

// 读取数据
UInt8 buffer[1024];
CFIndex bytesRead = CFReadStreamRead(readStream, buffer, sizeof(buffer));
NSLog(@"%ld bytes read", bytesRead);

CFReadStreamClose(readStream);
CFWriteStreamClose(writeStream);
CFRelease(readStream);
CFRelease(writeStream);

在 iOS 13 之后，`CFNetwork` 库被宣布废弃，推荐使用 `NSURLSession` 或 `Network.framework` 来创建网络连接。以下是使用 `NSURLSession` 创建 TCP 长连接的示例：

NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
config.allowsCellularAccess = YES;
config.timeoutIntervalForResource = 60.0;

NSURLSession *session = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:nil];

NSURL *url = [NSURL URLWithString:@"http://example.com"];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
request.HTTPMethod = @"GET";

NSURLSessionDataTask *task = [session dataTaskWithRequest:request];
[task resume];

在 `NSURLSessionDelegate` 协议中实现以下方法以处理响应：

- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data {
    NSLog(@"Received %ld bytes", [data length]);
}

- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {
    if (error) {
        NSLog(@"Request failed with error: %@", error);
    } else {
        NSLog(@"Request finished successfully");
    }
}