title: Python FIN Scan
body: <p>I'm trying to build a FIN scan with python3.5 using scapy. I send a FIN packet and in case the port is opened the server should ignore my request, in case it is closed I should get a RST packet back. I'm getting nothing and I've already tried many hosts, plus using an xmas scan I have the same problem. Am I doing something wrong? Here's the code : </p>
  
  <pre><code>...
  ip_p = IP(dst=host_ip)
  tcp_p  = TCP(dport=(1,100),flags='F')
  packets = ip_p/tcp_p
  resp, non_resp = sr(packets,timeout=0.5)
  for item in non_resp:
      print(item.sport)
  for sent,recv in resp:
      if recv[1].flags == 4 : # 4 == RST packet
          print('[&gt;]Port:',sent[1].dport,'closed, but !port service on!')
      if recv[1].flags != 4 :
          print('[!]Port:',sent[1].dport,'opened')
          print(recv[1].flags)
  </code></pre>