UDP connection issues

[deanfourie]

Hey Guys,

I have connection issues with an application over UDP. The connection involves an alarm panel (hardware TCP/UDP/IP Card) and the software.

Now, I am having huge issues connecting over UDP to this panel. I have a forward on the router at the alarm side for UDP/TCP port 3001.

I spoke to tech support, who told me I would also need a forward on the client (software side) initiating the connection. Now I have to say I disagreed and said that NAT would take care of the port mapping, knowing to forward all responses on port 3001 to my private IP.

Anyway, I did this and still NO luck, using ping.eu, I used port check and sure enough the port is showing as OPEN telling me that there is a path through to the TCP card and that its listening.

So I have setup

On the server side

Port 3001 -----> forwarded to internal host 192.168.x.x (255.255.255.0) UDP/TCP

On the client side I have

Port 3001 -----> forward to the client (initiating the connection) at 192.168.x.x (also 255.255.255.0) UDP/TCP

As the images below indicate, the port is unreachable and im also getting failed ICMP requests as I had ICMP disabled on the router, now I doubt that matters, but to be sure, I enabled ICMP on the router and still no go.

How can I tell if the connection is getting OUT on the client side, and how can I tell if this is a issues with the panel or router on the server side?

I need to sort this for work, and this client is getting rather angry. (its been a while).

Any ideas?

Thanks!!

PS.

Gateway is @ 192.168.0.254 - Router/PPP
DNS is @ 192.168.0.1 - Windows Server 2008 DNS Server
DHCP is @ 192.168.0.1 - Windows Server 2008 DHCP Server

Unsure if this is any use :P

[vnboost]

Are you sure all the client software needs is one UDP port, if so just select UDP in the router and not TCP/UDP, i would test this with the client software and wireshark on the LAN first to see.

Also the client does not need any forwarding all it needs is the external ip address to where the alarm panel is.

[deanfourie]

thats a good point, ill change it to a UDP forward and not TCP/UDP

I dont think thats it though

Ill give it a shot

[fromaron]

Are you using any firewalls on the server? Make sure you have the port open in the firewall as well (create an exception rule).
Also, it might be not the same with your setup, I am using Internet TV service which requires UDP connection to a range of ports open in order to have streaming without buffering. I can tell you, I tried three different routers and all they failed (couldn't establish UDP streaming, only TCP was running). Only one router worked - the router had port triggering as well. Even though people are saying the port triggering is not required these days but in my case that solved my streaming issues 100%.

[deanfourie]

Thanks for they reply,

There is no server running, just the router.

I dont think the port would be showing as OPEN if there were a firewall blocking it. The fact that the port shows as open indicates that there is a complete path to the IP Card and that that IP Card is listenning for connections.

I think my biggest problem is trying to determine if its client or server side that the problem resides. I cant really go deep in wireshark im not sure which layer traffic is actually comming to a stop at.

For all I know, this could be a simple layer 6 problem at (application). However I dont think so.

What i have is.

External IP of the router @ xxx.xxx.xxx.xxx
From there, there are 2x layer 2 switches conned, the second at which the IP card itself is connected at.
This is a single subnet network, no routing is taking place, no servers or any other equipment, very simple setup.

The client side however is running server 2008 acting as DHCP, DNS and router. I have even tried setting up static setting to go directly via the router with no luck (bypassing server 2008)

But again I go back to the basics that the port is however OPEN meaning that this may just be client side issue.

The software has nothing more to set then a simple IP, port and telling the software to use TCP/IP (over direct connect and modem connect etc)

Now theres the confusing part, its telling me TCP/IP but when I run a capture with wireshark its going out as UDP traffic.

So to sum thing up

xxx.xxx.xxx.xxx >> xxx.xxx.xxx.xxx >> forwarded on 3001 to 192.168.0.250

Its that simple lol.

Also, LAN connections appear to work fine.

Cheers