title: ios6.0.1 recvfrom always blocks on iphone
body: <p>We created a iOS app which performs UDP send operation (send request to server) in a thread (we use bsd socket API), another thread performs UDP receive operation (receive response from server) on the same socket.</p>
  
  <p>It works correctly on iOS 4/5, but when we tested it on iOS 6.0.1 (iPhone) it does not work, no problem found on iPad with iOS 6.0.1 and simulator.</p>
  
  <p>The app blocked on <code>recvfrom</code> infinitely, we are sure there is UDP response from server. 
  It seems that it's the same problem as this: <a href="https://groups.google.com/forum/#!msg/cocoaasyncsocket/rWokj2VO3VE/f-mZ6xWEUhkJ" rel="nofollow">https://groups.google.com/forum/#!msg/cocoaasyncsocket/rWokj2VO3VE/f-mZ6xWEUhkJ</a>.</p>
  
  <p>Code snippet:</p>
  
  <pre><code>char recvData[UDP_PACKAGE_LENGTH];
  bzero(recvData, UDP_PACKAGE_LENGTH);
  struct sockaddr_in fromAddr;
  uint32_t len = sizeof(fromAddr);
  int isHead = recvfrom(self-&gt;serverSock, recvData, UDP_PACKAGE_LENGTH, 0, (struct sockaddr*)(&amp;fromAddr), &amp;len);
  </code></pre>
  
  <p>Thanks for any help.</p>