title: TCP connection SYN packets being ignored, zero window size?
body: <p>I have an embedded device running an http client. Until now we have always used linux servers but recently have needed to use windows servers and am now having issues.</p>
  
  <p>My device opens a connection sends some data and then closes it ( not neccessarily gracefully as a reset or power failure can occur anytime!).
  What im finding is that after a few days at some locations only the server stops accepting new connections from the device.
  Originally I thought this might be due to trying to open a connection on already estabilished port as here: <a href="https://stackoverflow.com/questions/6825036/what-will-happen-if-i-send-a-syn-packet-to-the-server-when-there-has-already-bee">What will happen if I send a SYN packet to the server when there has already been a TCP connection established?</a>
  but now that I randomize the initial port value after boot up the issue still occurs (I would also expect the old connection to timeout).</p>
  
  <p>I have noticed several things that look strange:
  The SYN packet has a zero window size and a zero length, is this correct?
  It also has a zero sequence number, I think this is right?</p>
  
  <p>I apologize for lack of detail, I may be able to put up a link to a Wireshark capture at some point. The windows servers we are dealing with are also in 'the cloud' so I have very little in the way of access to server logs (which I find a bit ridiculous).</p>