title: Why is ACK = 1 and not 2 in first TCP request after connection establishment?
body: <p>I'm confused about the ACK and SEQ numbers in TCP packets right after the 3-way-handshake. I thought the ACK number is the next expected SEQ number.
  So when I analyse a TCP connection in Wireshark it says</p>
  
  <pre><code>TCP SYN with SEQ=0  
  TCP SYN ACK with SEQ 0, ACK=1 (clear, server expects SEQ 1 in next packet)  
  TCP ACK with SEQ 1, ACK=1 (clear, sender expects SEQ 1 in next packet)  
  
  HTTP Request: TCP PSH ACK with SEQ 1, ACK=1
  </code></pre>
  
  <p>The last line is unclear. I would say the sender expects SEQ=2 next, so it should be ACK=2? There was already a packet with SEQ=1 from the server, why does the sender want another one?</p>
  
  <p>Can someone explain this to me?</p>