ASIHTTPRequest

在ASIHTTPRequest.m文件中的startRequest方法（1180行左右）：

//
// Handle proxy settings
//

if (0) {
//if ([self proxyHost] && [self proxyPort]) {
// 这段代码不执行，不会使用系统默认的代理设置，能绕过Charles
  NSString *hostKey;
  NSString *portKey;

  if (![self proxyType]) {
   [self setProxyType:(NSString *)kCFProxyTypeHTTP];
  }

  if ([[self proxyType] isEqualToString:(NSString *)kCFProxyTypeSOCKS]) {
   hostKey = (NSString *)kCFStreamPropertySOCKSProxyHost;
   portKey = (NSString *)kCFStreamPropertySOCKSProxyPort;
  } else {
   hostKey = (NSString *)kCFStreamPropertyHTTPProxyHost;
   portKey = (NSString *)kCFStreamPropertyHTTPProxyPort;
   if ([[[[self url] scheme] lowercaseString] isEqualToString:@"https"]) {
    hostKey = (NSString *)kCFStreamPropertyHTTPSProxyHost;
    portKey = (NSString *)kCFStreamPropertyHTTPSProxyPort;
   }
  }
  NSMutableDictionary *proxyToUse = [NSMutableDictionary dictionaryWithObjectsAndKeys:[self proxyHost],hostKey,[NSNumber numberWithInt:[self proxyPort]],portKey,nil];

  if ([[self proxyType] isEqualToString:(NSString *)kCFProxyTypeSOCKS]) {
   CFReadStreamSetProperty((CFReadStreamRef)[self readStream], kCFStreamPropertySOCKSProxy, proxyToUse);
  } else {
   CFReadStreamSetProperty((CFReadStreamRef)[self readStream], kCFStreamPropertyHTTPProxy, proxyToUse);
  }
 }

AFNetworking