title: reply to udp packet is blocked
body: <p>I am writing a C program to search for smb shares on the local network and mount them.
  to get the hostnames of the smb servers found I send an udp nbns packet to the server.
  The packet is correct and the server replies.
  I am using wireshark to check this.
  I compared the packet I sent with a packet send by nbstat and I also compared the packets returned by the server.
  exept for the id and the checksum they are identical.</p>
  
  <p>when I do the request using nbstat the reply packet is received proper, but the reply to my own packet is probably blocked by the firewall.
  After receiving the reply from the server the client machine sends an icmp "Destination unreachable (Port unreachable)" message to the server.
  I suspect my firewall sending it.</p>
  
  <p>this is the output from wireshark</p>
  
  <p>No. Time      Source        Destination   Protocol Length Info<br>
  12  29.870065 192.168.1.245 192.168.1.21  NBNS     92     Name query NBSTAT *&lt;00>&lt;00.......<br>
  13  29.870494 192.168.1.21  192.168.1.245 NBNS     253    Name query response NBSTAT<br>
  14  29.870559 192.168.1.245 192.168.1.21  ICMP     281    Destination unreachable (Port unreachable)<br></p>
  
  <p>What should I do to allow the reply to pass?</p>