[Info-vax] FTP (was Re: unalphabetical help)

[Stephen Hoffman]

On 2013-01-05 21:09:26 +0000, David Froble said:

> Stephen Hoffman wrote:
>> On 2013-01-05 20:24:46 +0000, David Froble said:
>> 
>>> I've had only one problem with SmarTerm.  It supports an FTP session, 
>>> with command line or windows and drag and drop.  I've had a problem in 
>>> one direction with VMS on Alpha, never on VAX.  However, I've also had 
>>> a problem between 2 Alphas, which gets fixed by "SET PASSIVE" once an 
>>> FTP connection is established, so, I don't think it's a SmarTerm issue. 
>>> I've never bothered to study the "passive" thing with FTP, so I don't 
>>> know what the problem is, nor why setting "passive" fixes it.  I'm 
>>> guessing it's something to do with whichever side thinks it's in 
>>> control.  Perhaps improper handshake when the FTP connection is 
>>> established.
>> 
>> ftp requires a second connection be established either from the client 
>> to the server or from the server to the client, and many IP networks 
>> tend to have client-side or server-side firewalls or NAT devices that 
>> can block one or both of those additional connections.
> 
> ayep!  It's going through a firewall with a non-standard port accepting 
> incoming FTP connections.

Various newer ftp clients will silently default to trying both transfer 
modes.  If an active mode transfer fails to initiate, a passive mode 
transfer will be attempted.

The OpenVMS client does not provide that switch-over.

I've found sftp far easier to deal with within an IP network, as it 
uses just one port, and doesn't use it strangely.  (Caveat: there have 
been discussions here of the errors with the OpenVMS sftp 
implementation, though I've not generally encountered those errors.)


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