how do i connect to a comp that has an internal IP address ?

Factual Questions
21

ok… ideally, i’d like to run something like serv-u ftp on the home computer so that i have full ftp access to all my hard disks on the home computer from the office computer.

Urban Ranger and Mr2001 have got the IP and NAT issue correct… basically, one external ip address for multiple machines…

i’m well versed with security issues, so i wouldn’t be worried about any unauthorized attempts to connect to my systems…

so, basically, it looks like there would have to be initiation from the home pc to set up communication between the home and office PCs. The thing is, ideally, i would like to power on the home pc with ftp server running, leave home, reach office, connect at will. getting a connection going before i reach the office would seem difficult, considering there is no one at the office and the office pc is powered off until such time that i reach there.

i understand the issues, and know that in specific circumstances (e.g. leaving both PCs running 24/7, with a permanent link established) will aid the attempt. But what i’m really looking for is a workaround for this problem…

let’s assume we have determined that it is possible to get the required connection established if a link is initiated from the home pc.

so now let’s concentrate on this specific question:

can a similar link be established with initiation from the office pc, assuming an ftp server is running on the home pc, and taking into account the limitation that no modifications/mappings/etc can or will be made by the router handling the home pc ?

i thank you for your responses thus far… they have been enlightening and useful… and i am sure i shall incorporate most of your suggestions in the very near future, since i encounter a good number of varying networking scenarios in my everyday life…

22

No way.

I know that is a sucky answer (sorry), but due to the way FTP works you will not be able to use it in your current situation.

If you just want to browse files on your home computers hard drive rather than controlling it remotely, maybe something like ICQs built in file sharing would work. It isn’t the most graceful thing in the world, but I have used it before and it was adequate for my purposes.

23

My take is you need to work something out with your ISP. As far as I can tell what you need is to tunnel through the router, as it were, and a non-martian IP for your home PC.

Maybe they will do it for a fee.

24

I think there are probably things your could do to signal your home pc to start the connection process.

Here is one goofy way if you are running linux:
Have your home pc continually checking for email from an account that only it will use by sticking a fetchmail command into the crontab. As soon as a message is detected, it will initiate the connection process. Therefore to start your home computer connecting to your office computer, all you have to do is email it.

This is based on a little script I wrote for my computer to notify me of incoming email

here is my crontab:
*/15 * * * * /home/philip/qfetch >> /dev/null 2>&1

here is my program qfetch:

#!/bin/bash

fetchmail && /home/philip/mailsounds/mailbeep

  • other stuff I have cut here

This will run qfetch every 15 minutes to check for email. If it receives something when it runs fetchmail, it executes the program mailbeep. In your case, instead of executing mailbeep, execute the scripts needed to connect.

25

Just thinking about better ways to use this email method. Some person cleverer than me may descibe how to parse the subject line of an email so that only emails with subject line “start ftp” or something will initiate the connection process. This will prevent spam from triggering it.

26

An FTP server behind his dynamic NAT isn’t going to work at all, so there is little point in starting it.

27

I’ll defer to your greater knowledge. But how about using some other file transfer mechanism? When you download a file using a web browser, you’re not always using ftp right? If he had apache set up, could that work?

28

Or how about kermit which allows protocols “including Telnet, Rlogin, FTP, and HTTP”

29

I’m not a network admin, but I did stay at a Holiday Inn Express last night.

Great idea! Xash, the Kermit server supports scripting, so you could have your home machine initiate the connection. It also supports file transfers using the Kermit protocol, which NAT won’t break. You should check out that link that Balduran posted.

(Just don’t use it to set up an FTP server) :slight_smile: