Router – Can connect to VNC only when computer is connected to another vnc server

ipportroutervnc

I am having issues with a VNC. I am currently using Windows XP with UltraVNC. I am unable to connect to a vnc server. The only way for me to connect to the server is if I am connected to another VNC Server using the viewer.

Computer A
    |
Computer B

Computer C

Basically computer A can only view and can only be viewed if Computer B is connected to it via vnc. Computer C can see B without having any other VNC connections present. It's almost like ports are blocked when I am no longer connecting out. Previously I was able to connect to A, B, and C just fine. I have configured ports 5500 and 5900 in my routers firewall. Is there any reason why this should be happening?

I also used Microsofts tool called port query. I put in my external IP address and queried the port 5900 TCP and it came back with this message:

Starting portqry.exe -n 12.34.56.78 -e 5900 -p TCP ...

Querying target system called:

 12.34.56.78

Attempting to resolve IP address to a name...

IP address resolved to 12.34.56.78.p0.tel.com

querying...

TCP port 5900 (unknown service): FILTERED
portqry.exe -n 12.34.56.78 -e 5900 -p TCP exits with return code 0x00000002.

Here is what happens when I am not connected to a VNC using my vnc viewer

Starting portqry.exe -n 12.34.56.78 -e 5900 -p TCP ...

Querying target system called:

 12.34.56.78 

Attempting to resolve IP address to a name...

IP address resolved to 12.34.56.78 .tel.com

querying...

Error opening socket: 10065

No route to host. 
portqry.exe -n 12.34.56.78 -e 5900 -p TCP exits with return code 0x00000063.

I have obviously changed the Ip address, but is there anyone who knows what is going on here?

Thanks in advance.

Best Answer

If the server is behind a nat firewall/router, you have to do more than open a port in the firewall. You have to forward the port to the server.

So, if your router's external address is: 12.34.56.78 And your server's internal address is 192.168.1.2

Then you need to forward port 5900 on your router to 192.168.1.2:5900 which is your server.

Your correct in that 12.34.56.78 is not responding to connections. It's filtering all incoming connections.

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