Debugging the reason why your router cannot be found
Version 1 (Alan McGovern, 11/09/2009 12:59 AM) → Version 2/6 (Alan McGovern, 11/09/2009 01:03 AM)
h1. Debugging the reason why your router cannot be found
The uPnP specification is (generally speaking) badly implemented by a lot of router vendors. There are so many different quirks that I've come across that it's very hard to say whether or not a specific router will work with Mono.Nat. For Some routers do case sensitive matching on the cases where your router does not work, here's how soap messages. Some routers advertise the incorrect service. Some routers don't support the full range of port forwarding features, and there's no way to debug the issue. query this.
h2. Step 0: Enabling To help debug output
If you're running in a console application you these various incompatibilities, Mono.Nat can print debug information straight to the screen:
<pre>NatUtility.Logger = Console.Out;</pre>
If you want to be made log to a file, it's just as easy:
<pre>NatUtility.Logger = new StreamWriter (File.OpenWrite ("logfile.txt"));</pre>
If you fail to get past lot of useful information from each step 1 below, or just want all in the debug output, you should enable verbose mode:
<pre>NatUtility.Verbose = true</pre>
router discovery process.
h2. Step 1: Detecting available services
In order to detect what services are available on the local network, a udp broadcast message is sent. There are two kinds of message:
# The 'tell me everything you support' message
# The 'respond if you support service X' message
Mono.Nat uses the 'tell me everything you support' style message. I haven't come across a router which has failed to respond to this, though there are some which fail to respond to the second type of message. If your router fails at this step, then this is probably why. Typical output from this step is a dozen or so copies of the following:
<pre>
UPnP Response: HTTP/1.1 200 OK
SERVER: Ambit OS/1.0 UPnP/1.0 AMBIT-UPNP/1.0
EXT:
LOCATION: http://192.168.0.10:80/Public_UPNP_gatedesc.xml
CACHE-CONTROL: max-age=3600
ST: upnp:rootdevice
USN: uuid:e346a71d-99ef-86a6-3222-e9ba2bb3dfa0::upnp:rootdevice
UPnP Response: HTTP/1.1 200 OK
SERVER: Ambit OS/1.0 UPnP/1.0 AMBIT-UPNP/1.0
EXT:
LOCATION: http://192.168.0.10:80/Public_UPNP_gatedesc.xml
CACHE-CONTROL: max-age=3600
ST: urn:schemas-upnp-org:device:InternetGatewayDevice:1
USN: uuid:e346a71d-99ef-86a6-3222-e9ba2bb3dfa0::urn:schemas-upnp-org:device:InternetGatewayDevice:1
</pre>
h2. Step 2: Getting the service listing
If your router advertises one of the three services that Mono.Nat assumes will allow port forwarding, you will see output similar to this:
<pre>
UPnP Response: Router advertised a 'urn:schemas-upnp-org:service:WANIPConnection:' service
Found device at: http://192.168.0.10:80/Public_UPNP_gatedesc.xml
Parsed device as: 192.168.0.10:80
Fetching service list: 192.168.0.10:80
</pre>
h3. Step 3: Parsing a service listing
The service listing contains the details required to connect to the upnp service on the router. If the listing can be retrieved and parsed, you'll see output similar to this:
<pre>
192.168.0.10:80: Parsed services list
192.168.0.10:80: Found service: urn:schemas-upnp-org:service:Layer3Forwarding:1
192.168.0.10:80: Found service: urn:schemas-upnp-org:service:WANCommonInterfaceConfig:1
192.168.0.10:80: Found service: urn:schemas-upnp-org:service:WANIPConnection:1
192.168.0.10:80: Found upnp service at: /Public_UPNP_C3
192.168.0.10:80: Assuming control Uri is relative: /Public_UPNP_C3
192.168.0.10:80: Handshake Complete
</pre>
h4: Step 4: Using the device
Once the control Uri has been discovered, the DeviceFound event will be raised and you will be passed the INatDevice to use. From here you just need to make calls to the various methods like INatDevice.MapPort or INatDevice.GetExternalIP. It's worth noting that some devices will accept port maps which have a different internal IP address and external IP address, for example mapping external port 10000 to internal port 5000, while others will throw an exception. A few devices will silently ignore the internal port value and just map the external port 5000 to the internal port 5000.
h5. Submitting patches so your router works without modifications
If your router requires a fix to be detected with Mono.Nat, please let me know and supply a patch with the required changes. I'll gladly incorporate any changes which increase compatibility with different router models.