XPost: comp.os.vms   
   From: gah@ugcs.caltech.edu   
      
   Jeffrey H. Coffield  wrote:   
   > We had a customer complain that one of their customers could only ftp 3   
   > files at a time as the fourth would fail. Even if they sent the files   
   > one at a time, the fourth would generally, but not always fail. Turning   
   > on the FTP debugging showed a 425 duplicate name error on port 5004.   
   > They asked me to see if there was some firewall settings that was   
   > blocking that port.   
      
   > After quite a bit of digging, I saw that when the ftp session started,   
   > it always used port 5001 first, then 5002, 5003 and fail on 5004.   
   > Finally a "TPCIP show device" showed there was a bg device open on port   
   > 5004.   
      
   I presume the is not passive-ftp, which is more usual these days,   
   especially as it gets through firewalls easier.   
      
   I am cross-posting to comp.protocols.tcp-ip.  In general, a TCP   
   connection is identified by the quad of source address, source port,   
   destination address, destination port.  If even one is different,   
   a new connection can be made.  When non-passive ftp opens the port   
   for the transfer, I would expect (and those in comp.protocols.tcp-ip   
   will note if I am wrong) that it should set all four, such that it   
   would not fail if another connection was open on 5004.   
      
   It seems like a VMS bug to me, though.   
      
   -- glen   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)