Idot's Guide to Real VNC on Netgear Broadband Router

Posted on 2003-12-08
Medium Priority
Last Modified: 2012-08-14
I am trying to access my sisters computer which is at another location.  She has Real VNC Server installed and I have the viewer.  She is using W2K, and has a wireless USB Netgear Adaptor, which is connecting her to a Wireles Netgear broadband rounter (which I think has a built-in firewall).

When she runs the Real VNC server, the protocal that appears is:

When I run the Real VNC viewer and try to connect to the protocal, I get an error "Failed to connect to server."

How can I connect to her machine?

Question by:semmes
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LVL 31

Expert Comment

ID: 9900728
Oh, well, you got the wrong answer.  You have to understand two things: 1) what a UNID is, and 2) how it is formed.

The API User Guide explains UNIDs.  (Although the title misnames them Note IDs.)  The UNID has two parts, the UNID.File and UNID.Note.  Each is a 16-digit hex number.  Starting with Notes 3.0, it is a random number.  UNID.Note is the time-date that the document was created.

So, by pure happenstance, it is unlikely that two documents would share a UNID.  They would have to coincidentally be created at the same time (or its equivalent, given clock inaccuracies).  And it would have a 1/2^128 chance even given taht possibility.  On the same server, it is even less likely, because the busy time the server has when creating the note typically precludes another document getting created in the same clock tick (not to be confused with CPU clock cycle), and teh random number generation routine more or less precludes the server from using the same random number twice in a row.

That saud, all the above is a lie.  Smetimes.  Aside from the fact that the UNID can be manipulated (an accident Bob Balaban made, I think), there are situations where Notes contrives to re-use a UNID.  When documents are moved from one database to another, Notes OMSTIMES attempts to keep the UNID of the original document.  It does this, for example, in certain versions, on cut and paste, so it does not have to recalculate $Ref values.  The router does this for mail thread tracking.  So, i all likelihood, if you have two mail users on a single server who communicate with each other, they have common UNIDs in their mail databases, so the likelihood is actually quite HIGH that Arun's situation will occur, at least for mail.
LVL 31

Expert Comment

ID: 9900732
My apologies, QuickPost jumped threads on me, please ignore the above message.
LVL 31

Accepted Solution

qwaletee earned 400 total points
ID: 9900806
I hope the follownig "good comment" makes up for the "bad comments" above.

192.168.x.y is a "private" address space.  The NetGear is what is called a "NAT" router -- network address translation.  This allows the broadband provider to assign her only a single IP address, yet whe can use it with multiple computers.  the NAT routers Tramslates the Network Addresses that she uses on the "inside" computers behind the forewall) and the single outside address.

So, you need to know what th outside address is.  If it is a static address (unlikely), then you are most of the way there.  If it is a dynamic address, then it can change constantly, making this rather difficult.

Let;s say you know the addess (static, or you just checked what her current dynamic address is).  the next issue is that the firewall (NetGear) will not let the traffic through.  You have to enable port forwaring on teh NetGear, then port forward port 5900 (the default VNC port) to -- with another gotcha.  Usually, the NAT addresses are also dynamic.  It is possible that address will change as well.  You can set up static addressing inside the firewall, which will at least remove that issue.

Now, how do you find the external dynamic address?  You can use one of the DYnamic DNS services to assign a hostname that frequently updates itself to whatever the dynamic address is.  Or, if your sister will be home when you do teh VNC, you can have her go to teh NetGear admin screen, and read off whatever it shows to be its current address.

Actually, if she is there, then you have another way arond it.  Yo can run teh VNC Viewer in "listening" mode.  Normally, you start the VNC server at the "host" machine, and it just sits "listening" for you to have a viewer call the server.  In the listening viewer, you do almost the opposite. You start the viewer in listen mode, and it waits for the SERVER TO CALL TEH VIEWER! your sister can right-click on te VNC tray icon, choose ADD CLIENT from the pop-up menu, and type your IP address.

Of course, if you have a dynamic IP or a frewall, then you will have all the same problems mentinoed above, just in reverse!  The viwer normally listens on port 550, by the way.
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LVL 18

Expert Comment

ID: 9901204
open ports 5800 5801 5900 5901 (assuming you'll only have one or two viewers, one for web one for the client)
You need to make the inside client's address static and open those ports to it.
You then need to know the outside address, which you can get from the router infornation page (it changes periodically, the above tip on dynamic dns works but you have to configure the netgear to notify the dynamic dns provider and understand it could take hours to days to change on a particular DNS server)
LVL 10

Expert Comment

ID: 9907414
And remember to turn the VNC server off when you have done as you are leaving a nice point of attack otherwise, also the actual data being sent back and forth has very simple protection so can be cracked if somebody has a mind to.
LVL 18

Expert Comment

ID: 9907992
unless you run it over ssh

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