[Tutor] control multiple FTP sessions using multiple ipconnectionsvia different com ports

David Perlman dperlman at wisc.edu
Mon Feb 19 14:51:30 CET 2007

This kind of thing is usually handled at the level of the OS's  
routing table.  Routing tables have an entry called "metric" that is  
used to weight the different routes, so that when there are multiple  
possible links available, the one with the lowest metric is used  
first.  In Unix at least, you'll be able to use either the command  
"route" or "routed" to manually change the routing table; you can  
change the metrics for the two interfaces to control which one gets  
used.  unfortunately this will change the routing globally, not just  
for a specific connection.  I don't think the routing systems on  
ordinary computers were designed with the idea in mind that you might  
want to use a specific link for a specific connection.

If you're on UNIX, run netstat -nr.  If you're on Windoze, run route  
print.  You should be able to see the metric for each entry.
Unfortunately, the "metric" column doesn't show up under OS X, and I  
haven't been able to figure out why in 5 minutes of searching.  Also  
unfortunately, I don't know any more about this, and searching on  
Google was not revealing immediate results.  But hopefully this will  
get you started in the right direction!

So the bottom line, I guess, is that a) this is a routing question,  
not a python question; and b) it's not an easy question.  :)

On Feb 19, 2007, at 3:53 AM, ray sa wrote:

> Hi
> Well now I have configured an old machine in the garage to run at  
> the same time.
> I would really like to find out how to do this as it must be  
> possible. I have been googling like mad and can't find how. Kind of  
> frustrating when you don't know how. At the same time a challenge  
> to seek.
> I am kind of hoping that someone on this forum will know how. In  
> the mean time I can continue with my testing.
> Many thanks for your help; really appreciate it.
> /Ray
> Johan Geldenhuys <johan at accesstel.co.za> wrote:
> Will it be possible to disconnect one of the links during your test  
> and reconnect it and disconnect the other connection once the ftp  
> test is finished on the first connection? This way it will force  
> the test script to use the active route to the internet.
> Not the most elegant way, but something to look at in the mean time.
> Johan
> From: tutor-bounces at python.org [mailto:tutor-bounces at python.org] On  
> Behalf Of ray sa
> Sent: 18 February 2007 04:16 AM
> To: Alan Gauld; tutor at python.org
> Subject: Re: [Tutor] control multiple FTP sessions using multiple  
> ipconnectionsvia different com ports
> Hi Alan et al
> Many thanks for your time on this.
> I was referring to the client end.
> An EDGE terminal is a phone that has the capability of connecting  
> to the internet. We use mobile phones to make a voice call that  
> make use of a circuit switched connection. By using a GPRS  
> connection we can use the mobile device to connect to the packet  
> switched domain. You might have heard about making data connection  
> using your phone like GPRS, 3G etc. EDGE is just faster than a GPRS  
> connection and 3G is supposedly faster than GPRS and EDGE.
> May be I can give you more information about what I am trying to  
> do. So you can understand what I am trying to achieve. Basically, I  
> am trying to decide whether I should change my ADSL fixed solution  
> to a higher speed connection using a mobile solution. Where I live  
> the mobile operator is offering a mobile solution which is cheaper  
> than my fixed solution….and is faster than my ADSL connection,  
> please read on
> I have my ADSL broadband connection to my service provider that I  
> use to connect to the internet. I have just bought a GPRS/EDGE/3G  
> terminal and wanted to benchmark the speed I am getting by using my  
> mobile device as opposed to my fixed connection.
> My desktop machine is connected to my ADSL provider using a USB  
> modem which is assigned a particular COM port on my machine. Then I  
> have connected my mobile handset also using a USB connection  
> connected to a different COM port.
> Now I have two ip addresses
> ADSL – COM port 4 with ip addres from my ADSL service provider
> Mobile Handset – COM port 5 with another ip address from my mobile  
> provider
> I have written a script that connects to a ftp server within my  
> home country and downloads a file. But this script uses one of the  
> connections above. There must be away to tell the script and  
> control which connection to use. So I can get to see real time  
> which connection is faster. So I can run the script pointing to one  
> IP address and at the same time run another script using the other  
> connection.
> I think there must be a method that finds out which connection is  
> connected to which com port and then in my script I need to point  
> towards that connection so my script knows which channel to use  
> when downloading the file.
> I hope this helps sorry for too much text couldn’t really find a  
> simpler way to explain this.
> Once again I really appreciate the help on this forum...../Ray
> Alan Gauld <alan.gauld at btinternet.com> wrote:
> "ray sa" wrote
> > I have been successful to write an ftp script that logs
> > into a server and collects files.
> > ...I would like to run multiple ftp sessions using one laptop
> > with two different connections.
> Do you mean you want the server on the laptop accepting
> using two connections or do you mean that you want
> the client on the laptop and have different sessions sending
> outgoing requests to the server via two different IP addresses?
> If the former its easy, just set up two servers, one on each
> IP address. The port will nbe the same on both, ISTR its port
> 21 for ftp?
> If you want to specify which IP address you send the
> client request from, I'm afraid I have no idea how you specify
> that. I've only ever used multiple network cards at the server
> end!
> > another connection using your EDGE terminal
> As a matter of interest what is an EDGE terminal?
> A new term for me...
> > I would like to write a script that controls which ip
> > address to use or with com port to use.
> Until we know which end you mean its hard to hgive more
> specific advice.
> Alan G.
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