I'm a biologist with a number of Macs in the lab running OS X. One of my
Macs has a static IP address, so I can access it from home. The others have
dynamic addresses. I figure, one way for me to access them from home is to
run a little program on each one which would, every 30 minutes or so, open
an FTP connection to my static Mac and dump their name and current IP
address to a 1-line file (replacing the old one). That way, all I have to do
is log onto my static Mac, check the files, and find the current IP address
of each of my machines. If anyone has a better scheme, I'd love to hear it.
Otherwise, does anyone have or know of a code snippet like this? I know it's
probably not too tough to write; somewhere there must be a public-domain C
library which implements FTP client-side functions. Or perhaps there's a
quick Perl script around which does this. Can anyone help?

--

Mike Levin
mlevin77@comcast.net

In article <BD31516E.1B583%mlevin77@comcast.net>,
Michael Levin <mlevin77@comcast.net> wrote:

> I'm a biologist with a number of Macs in the lab running OS X. One of my
> Macs has a static IP address, so I can access it from home. The others have
> dynamic addresses. I figure, one way for me to access them from home is to
> run a little program on each one which would, every 30 minutes or so, open
> an FTP connection to my static Mac and dump their name and current IP
> address to a 1-line file (replacing the old one). That way, all I have to do
> is log onto my static Mac, check the files, and find the current IP address
> of each of my machines. If anyone has a better scheme, I'd love to hear it.
> Otherwise, does anyone have or know of a code snippet like this? I know it's
> probably not too tough to write; somewhere there must be a public-domain C
> library which implements FTP client-side functions. Or perhaps there's a
> quick Perl script around which does this. Can anyone help?

You don't say who issues the dynamic IP addresses. If they are being
issued by an ISP, you can use a service like DynDns
(<http://www.dyndns.org/services/dyndns/> to register a domain name and
download a client which will keep the mapping up to date. If the
dynamic IP addresses are issued by a local router, you will have to
configure the router to map selected ports through to the target
machines. Specifics of the mapping are router dependent.

--
There are 10 kinds of people in the world:
those who understand binary, and those who don't.

Tom Stiller

PGP fingerprint = 5108 DDB2 9761 EDE5 E7E3
7BDA 71ED 6496 99C0 C7CF

In article <BD31516E.1B583%mlevin77@comcast.net>,
Michael Levin <mlevin77@comcast.net> wrote:

> I'm a biologist with a number of Macs in the lab running OS X. One of my
> Macs has a static IP address, so I can access it from home. The others have
> dynamic addresses. I figure, one way for me to access them from home is to
> run a little program on each one which would, every 30 minutes or so, open
> an FTP connection to my static Mac and dump their name and current IP
> address to a 1-line file (replacing the old one). That way, all I have to do
> is log onto my static Mac, check the files, and find the current IP address
> of each of my machines. If anyone has a better scheme, I'd love to hear it.
> Otherwise, does anyone have or know of a code snippet like this? I know it's
> probably not too tough to write; somewhere there must be a public-domain C
> library which implements FTP client-side functions. Or perhaps there's a
> quick Perl script around which does this. Can anyone help?

http://no-ip.com
http://dyndns.org

If these are real IP addresses (not the hidden non-routing addresses),
then you should be able to use either No-IP.com or DynDNS.org to get a
free DNS name and a utility to run on your Macs that will update
No-IP.com or DynDNS.org as to what your current IP address is.

I happen to use No-IP.com on my Mom's iMac. I then ssh tunnel into her
system and run OSXvnc and Chicken of the VNC to manage her system
remotely.

Now if you are using a non-routing DHCP address, such as 192.168.*.*, or
10.*.*.*, then No-IP and DynDNS would only find your router's internet
connection IP address. This can still be used to some advantage if you
have your router forward explicit ports to your individual Macs. For
example port 22 is the SSH port, you could have different ports
forwarded for each machine, and then arrange for those ports to be
monitored on your Macs as SSH connections. Once you ssh log into the
system you can get your current non-routing IP address that way.

Bob Harris

On 7/31/04 12:58 PM, in article
harris-3096A3.13582531072004@cacnews.cac.cpqcorp.net, "Bob Harris"
<harris@zk3.dec.com> wrote:

> In article <BD31516E.1B583%mlevin77@comcast.net>,
> Michael Levin <mlevin77@comcast.net> wrote:
>
>> I'm a biologist with a number of Macs in the lab running OS X. One of my
>> Macs has a static IP address, so I can access it from home. The others have
>> dynamic addresses. I figure, one way for me to access them from home is to
>> run a little program on each one which would, every 30 minutes or so, open
>> an FTP connection to my static Mac and dump their name and current IP
>> address to a 1-line file (replacing the old one). That way, all I have to do
>> is log onto my static Mac, check the files, and find the current IP address
>> of each of my machines. If anyone has a better scheme, I'd love to hear it.
>> Otherwise, does anyone have or know of a code snippet like this? I know it's
>> probably not too tough to write; somewhere there must be a public-domain C
>> library which implements FTP client-side functions. Or perhaps there's a
>> quick Perl script around which does this. Can anyone help?
>
> http://no-ip.com
> http://dyndns.org
>
> If these are real IP addresses (not the hidden non-routing addresses),
> then you should be able to use either No-IP.com or DynDNS.org to get a
> free DNS name and a utility to run on your Macs that will update
> No-IP.com or DynDNS.org as to what your current IP address is.
>
> I happen to use No-IP.com on my Mom's iMac. I then ssh tunnel into her
> system and run OSXvnc and Chicken of the VNC to manage her system
> remotely.
>
> Now if you are using a non-routing DHCP address, such as 192.168.*.*, or
> 10.*.*.*, then No-IP and DynDNS would only find your router's internet
> connection IP address. This can still be used to some advantage if you
> have your router forward explicit ports to your individual Macs. For
> example port 22 is the SSH port, you could have different ports
> forwarded for each machine, and then arrange for those ports to be
> monitored on your Macs as SSH connections. Once you ssh log into the
> system you can get your current non-routing IP address that way.
>
> Bob Harris

I am a LAN Manager at Vanderbilt University Medical Center. Unless your DHCP
server is set up differently, your computers will retain their IP addresses
indefinitely. Ours actually has a "lease" time of three days, but if the
computer remains on, it retains the same IP.
--
Brian Ehni

On 7/31/04 1:49 PM, in article
tomstiller-C55B10.13494731072004@com...a.giganews.com, "Tom Stiller"
<tomstiller@comcast.net> wrote:

> In article <BD31516E.1B583%mlevin77@comcast.net>,
> Michael Levin <mlevin77@comcast.net> wrote:
>
>> I'm a biologist with a number of Macs in the lab running OS X. One of my
>> Macs has a static IP address, so I can access it from home. The others have
>> dynamic addresses. I figure, one way for me to access them from home is to
>> run a little program on each one which would, every 30 minutes or so, open
>> an FTP connection to my static Mac and dump their name and current IP
>> address to a 1-line file (replacing the old one). That way, all I have to do
>> is log onto my static Mac, check the files, and find the current IP address
>> of each of my machines. If anyone has a better scheme, I'd love to hear it.
>> Otherwise, does anyone have or know of a code snippet like this? I know it's
>> probably not too tough to write; somewhere there must be a public-domain C
>> library which implements FTP client-side functions. Or perhaps there's a
>> quick Perl script around which does this. Can anyone help?
>
> You don't say who issues the dynamic IP addresses. If they are being
> issued by an ISP, you can use a service like DynDns
> (<http://www.dyndns.org/services/dyndns/> to register a domain name and
> download a client which will keep the mapping up to date. If the
> dynamic IP addresses are issued by a local router, you will have to
> configure the router to map selected ports through to the target
> machines. Specifics of the mapping are router dependent.

they're issued by our system administrator - the building is on a T1 line,
and they have a server which hands out IP addresses to any machines plugged
into the ethernet. Actually, I already have my own domain name registered.
Is that sufficient for DYNDNS or do I have to pay them again? Does their
client run on OS X? The port mapping is an issue - I forgot about it. I
guess I have to ask our sysadmin...

--

Mike Levin
mlevin77@comcast.net

On 7/31/04 1:58 PM, in article
harris-3096A3.13582531072004@cacnews.cac.cpqcorp.net, "Bob Harris"
<harris@zk3.dec.com> wrote:

> In article <BD31516E.1B583%mlevin77@comcast.net>,
> Michael Levin <mlevin77@comcast.net> wrote:
>
>> I'm a biologist with a number of Macs in the lab running OS X. One of my
>> Macs has a static IP address, so I can access it from home. The others have
>> dynamic addresses. I figure, one way for me to access them from home is to
>> run a little program on each one which would, every 30 minutes or so, open
>> an FTP connection to my static Mac and dump their name and current IP
>> address to a 1-line file (replacing the old one). That way, all I have to do
>> is log onto my static Mac, check the files, and find the current IP address
>> of each of my machines. If anyone has a better scheme, I'd love to hear it.
>> Otherwise, does anyone have or know of a code snippet like this? I know it's
>> probably not too tough to write; somewhere there must be a public-domain C
>> library which implements FTP client-side functions. Or perhaps there's a
>> quick Perl script around which does this. Can anyone help?
>
> http://no-ip.com
> http://dyndns.org
>
> If these are real IP addresses (not the hidden non-routing addresses),
> then you should be able to use either No-IP.com or DynDNS.org to get a
> free DNS name and a utility to run on your Macs that will update
> No-IP.com or DynDNS.org as to what your current IP address is.
>
> I happen to use No-IP.com on my Mom's iMac. I then ssh tunnel into her
> system and run OSXvnc and Chicken of the VNC to manage her system
> remotely.
>
> Now if you are using a non-routing DHCP address, such as 192.168.*.*, or
> 10.*.*.*, then No-IP and DynDNS would only find your router's internet
> connection IP address. This can still be used to some advantage if you
> have your router forward explicit ports to your individual Macs. For
> example port 22 is the SSH port, you could have different ports
> forwarded for each machine, and then arrange for those ports to be
> monitored on your Macs as SSH connections. Once you ssh log into the
> system you can get your current non-routing IP address that way.
>
> Bob Harris

Great - thanks!!

--

Mike Levin
mlevin77@comcast.net

In article <BD316A0F.1B65B%mlevin77@comcast.net>,
Michael Levin <mlevin77@comcast.net> wrote:

> On 7/31/04 1:49 PM, in article
> tomstiller-C55B10.13494731072004@com...a.giganews.com, "Tom Stiller"
> <tomstiller@comcast.net> wrote:
>
> > In article <BD31516E.1B583%mlevin77@comcast.net>,
> > Michael Levin <mlevin77@comcast.net> wrote:
> >
> >> I'm a biologist with a number of Macs in the lab running OS X. One
> >> of my Macs has a static IP address, so I can access it from home.
> >> The others have dynamic addresses. I figure, one way for me to
> >> access them from home is to run a little program on each one which
> >> would, every 30 minutes or so, open an FTP connection to my static
> >> Mac and dump their name and current IP address to a 1-line file
> >> (replacing the old one). That way, all I have to do is log onto my
> >> static Mac, check the files, and find the current IP address of
> >> each of my machines. If anyone has a better scheme, I'd love to
> >> hear it. Otherwise, does anyone have or know of a code snippet
> >> like this? I know it's probably not too tough to write; somewhere
> >> there must be a public-domain C library which implements FTP
> >> client-side functions. Or perhaps there's a quick Perl script
> >> around which does this. Can anyone help?
> >
> > You don't say who issues the dynamic IP addresses. If they are being
> > issued by an ISP, you can use a service like DynDns
> > (<http://www.dyndns.org/services/dyndns/> to register a domain name and
> > download a client which will keep the mapping up to date. If the
> > dynamic IP addresses are issued by a local router, you will have to
> > configure the router to map selected ports through to the target
> > machines. Specifics of the mapping are router dependent.
>
> they're issued by our system administrator - the building is on a T1 line,
> and they have a server which hands out IP addresses to any machines plugged
> into the ethernet. Actually, I already have my own domain name registered.
> Is that sufficient for DYNDNS or do I have to pay them again? Does their
> client run on OS X? The port mapping is an issue - I forgot about it. I
> guess I have to ask our sysadmin...

I guess the real question is: given the current IP address of one of the
machines in question, can you connect to it from home? If the answer is
yes, then registration with a service like dyndns and running an
available client on the target machine to keep the mapping up to date is
all that is required. If you can't access the target machine via its
(known) IP address, you will have to negotiate with your sysadmin to
provide the appropriate routing.

--
There are 10 kinds of people in the world:
those who understand binary, and those who don't.

Tom Stiller

PGP fingerprint = 5108 DDB2 9761 EDE5 E7E3
7BDA 71ED 6496 99C0 C7CF

Michael Levin <mlevin77@comcast.net> wrote:

> Is that sufficient for DYNDNS or do I have to pay them again?

No, their service is free if you accept one of their own domains, see:

<http://www.dyndns.org/services/dyndns/domains.html>

it's free for up to 5 names...

HC

On 7/31/04 4:12 PM, in article
tomstiller-7D8CF5.16125231072004@com...a.giganews.com, "Tom Stiller"
<tomstiller@comcast.net> wrote:

> In article <BD316A0F.1B65B%mlevin77@comcast.net>,
> Michael Levin <mlevin77@comcast.net> wrote:
>
>> On 7/31/04 1:49 PM, in article
>> tomstiller-C55B10.13494731072004@com...a.giganews.com, "Tom Stiller"
>> <tomstiller@comcast.net> wrote:
>>
>>> In article <BD31516E.1B583%mlevin77@comcast.net>,
>>> Michael Levin <mlevin77@comcast.net> wrote:
>>>
>>>> I'm a biologist with a number of Macs in the lab running OS X. One
>>>> of my Macs has a static IP address, so I can access it from home.
>>>> The others have dynamic addresses. I figure, one way for me to
>>>> access them from home is to run a little program on each one which
>>>> would, every 30 minutes or so, open an FTP connection to my static
>>>> Mac and dump their name and current IP address to a 1-line file
>>>> (replacing the old one). That way, all I have to do is log onto my
>>>> static Mac, check the files, and find the current IP address of
>>>> each of my machines. If anyone has a better scheme, I'd love to
>>>> hear it. Otherwise, does anyone have or know of a code snippet
>>>> like this? I know it's probably not too tough to write; somewhere
>>>> there must be a public-domain C library which implements FTP
>>>> client-side functions. Or perhaps there's a quick Perl script
>>>> around which does this. Can anyone help?
>>>
>>> You don't say who issues the dynamic IP addresses. If they are being
>>> issued by an ISP, you can use a service like DynDns
>>> (<http://www.dyndns.org/services/dyndns/> to register a domain name and
>>> download a client which will keep the mapping up to date. If the
>>> dynamic IP addresses are issued by a local router, you will have to
>>> configure the router to map selected ports through to the target
>>> machines. Specifics of the mapping are router dependent.
>>
>> they're issued by our system administrator - the building is on a T1 line,
>> and they have a server which hands out IP addresses to any machines plugged
>> into the ethernet. Actually, I already have my own domain name registered.
>> Is that sufficient for DYNDNS or do I have to pay them again? Does their
>> client run on OS X? The port mapping is an issue - I forgot about it. I
>> guess I have to ask our sysadmin...
>
> I guess the real question is: given the current IP address of one of the
> machines in question, can you connect to it from home? If the answer is
> yes, then registration with a service like dyndns and running an
> available client on the target machine to keep the mapping up to date is
> all that is required. If you can't access the target machine via its
> (known) IP address, you will have to negotiate with your sysadmin to
> provide the appropriate routing.

right. Worst comes to worst, what I'll do is ssh in to the static machine
(which I know I can do), and from there, ssh to the other machines, once I
know what their address is. That should get around the port rules and
firewall business, right?

--

Mike Levin
mlevin77@comcast.net

In comp.sys.mac.system Michael Levin <mlevin77@comcast.net> exponit:
> I'm a biologist with a number of Macs in the lab running OS X. One of my
> Macs has a static IP address, so I can access it from home. The others have
> dynamic addresses. I figure, one way for me to access them from home is to
> run a little program on each one which would, every 30 minutes or so, open
> an FTP connection to my static Mac and dump their name and current IP
> address to a 1-line file (replacing the old one). That way, all I have to do
> is log onto my static Mac, check the files, and find the current IP address
> of each of my machines. If anyone has a better scheme, I'd love to hear it.
> Otherwise, does anyone have or know of a code snippet like this? I know it's
> probably not too tough to write; somewhere there must be a public-domain C
> library which implements FTP client-side functions. Or perhaps there's a
> quick Perl script around which does this. Can anyone help?

In our lab here at UC Davis, we run our own network, using the
university-assigned IP as a gateway. If you want to access the
network easily from home, you can simply tunnel in through the
gateway & your home machine is "in" the lab network.

We use FreeBSD in our gateway machine, but I'm confident that it
could be done just as well with an OS/X machine.

Greg Shenaut

On 7/31/04 6:29 PM, in article 1ghtag9.l5d14z1tpq246N%bounce.this@rude.com,
"Hugh Chaloner" <bounce.this@rude.com> wrote:

> Michael Levin <mlevin77@comcast.net> wrote:
>
>> Is that sufficient for DYNDNS or do I have to pay them again?
>
> No, their service is free if you accept one of their own domains, see:
>
> <http://www.dyndns.org/services/dyndns/domains.html>
>
> it's free for up to 5 names...
>
> HC

ah, cool! Now, several people have pointed out that due to our firewall, I
may not be able to get to the dynamic IP machines from outside anyway. This
is true. So, my plan now is to ssh in to the static machine, and knowing the
IP address of the others, ssh to them from inside. Sounds like it should
work. The question is: does the client software I just downloaded from
DYNDNS help me with that or does it only work directly with the DYNDNS
service (which I guess I can't use, since the machines won't be allowed
direct contact from outside)? What exactly does their client software do -
where does it put the IP address info?

--

Mike Levin
mlevin77@comcast.net

On 7/31/04 7:08 PM, in article ceh8ps$t2a$1@woodrow.ucdavis.edu, "Greg
Shenaut" <gkshenaut@ucdavis.edu> wrote:

> In comp.sys.mac.system Michael Levin <mlevin77@comcast.net> exponit:
>> I'm a biologist with a number of Macs in the lab running OS X. One of my
>> Macs has a static IP address, so I can access it from home. The others have
>> dynamic addresses. I figure, one way for me to access them from home is to
>> run a little program on each one which would, every 30 minutes or so, open
>> an FTP connection to my static Mac and dump their name and current IP
>> address to a 1-line file (replacing the old one). That way, all I have to do
>> is log onto my static Mac, check the files, and find the current IP address
>> of each of my machines. If anyone has a better scheme, I'd love to hear it.
>> Otherwise, does anyone have or know of a code snippet like this? I know it's
>> probably not too tough to write; somewhere there must be a public-domain C
>> library which implements FTP client-side functions. Or perhaps there's a
>> quick Perl script around which does this. Can anyone help?
>
> In our lab here at UC Davis, we run our own network, using the
> university-assigned IP as a gateway. If you want to access the
> network easily from home, you can simply tunnel in through the
> gateway & your home machine is "in" the lab network.
>
> We use FreeBSD in our gateway machine, but I'm confident that it
> could be done just as well with an OS/X machine.
>
> Greg Shenaut

Yep - that's my plan now, I can use ssh. But, once I get into the gateway
machine, I still somehow need to know the IP address currently owned by the
box I'm trying to get to. I am looking for a simple way to have my lab
machines save their IP addresses to a file on the gateway.

--

Mike Levin
mlevin77@comcast.net

Michael Levin <mlevin77@comcast.net> wrote:

> Now, several people have pointed out that due to our firewall, I
> may not be able to get to the dynamic IP machines from outside anyway.

But I thought you said you could login to your work machine remotely -
earlier in the thread? If this is the case, then the firewall has
already allowed you through. Is the static machine (you were talking
about earlier) behind the firewall?

> So, my plan now is to ssh in to the static machine, and knowing the
> IP address of the others, ssh to them from inside.

Are you using X11? you can do all sorts of fancy tunnelling with ssh &
X11.

> Sounds like it should
> work. The question is: does the client software I just downloaded from
> DYNDNS help me with that or does it only work directly with the DYNDNS
> service (which I guess I can't use, since the machines won't be allowed
> direct contact from outside)? What exactly does their client software do -
> where does it put the IP address info?

There are extensive FAQs on the dyndns site which may answer your
questions. I'm not sure i understand them completely.

Your machines will appear as ONE ip address to the outside world - that
will be the ip of your router / firewall.

HC

In article <1ghtduz.nwse0ri9g73aN%bounce.this@rude.com>, Hugh Chaloner
<bounce.this@rude.com> wrote:

> Michael Levin <mlevin77@comcast.net> wrote:
>
> > Now, several people have pointed out that due to our firewall, I
> > may not be able to get to the dynamic IP machines from outside anyway.
>
> But I thought you said you could login to your work machine remotely -
> earlier in the thread? If this is the case, then the firewall has
> already allowed you through. Is the static machine (you were talking
> about earlier) behind the firewall?

No. If I remember correctly, he has access to one machine with a static
address, and would like to access others which have locally assigned
dynamic addresses.

Rob.

In article <BD319D99.1B67A%mlevin77@comcast.net>,
Michael Levin <mlevin77@comcast.net> wrote:

> right. Worst comes to worst, what I'll do is ssh in to the static machine
> (which I know I can do), and from there, ssh to the other machines, once I
> know what their address is. That should get around the port rules and
> firewall business, right?

That will work and that brings us back to your original question. Maybe
the simplest gimmick is to have the target machine email its IP address
to the known machine where it can be read in the first hop and used to
complete the second hop.

--
There are 10 kinds of people in the world:
those who understand binary, and those who don't.

Tom Stiller

PGP fingerprint = 5108 DDB2 9761 EDE5 E7E3
7BDA 71ED 6496 99C0 C7CF