A co-worker just reminded me that I promised to discuss the effects a home network could have on your Indigo Service, and how that could differ based on the transport you are using.

The first thing to realize about a home network is that your computer is likely behind a NAT. Most DSL or Cable routers will act in this role. The router is assigned an IP Address from your service provider via DHCP, and therefore your router is the only member of your network that is globally addressable. Which means that while you can connect to other machines on the internet, they cannot connect to you.

The practical upshot of this situation is that you cannot use the “dual” standard bindings (a.k.a. WsProfileDualHttpBinding and NetProfileDualTcpBinding) to access services located outside of your home network. Which won’t affect you unless you are using a duplex service contract. I can already hear you saying “but duplex contracts are incredibly useful!” Yes they are. And if you want to use them from behind a NAT you have 2 options:

1. Use NetProfileTcpBinding. This will allow you to be the client for duplex communication with another Indigo endpoint.
2. Host a router service on the Internet. This is a complicated solution that entails bridging the TCP connection from your home machine to a dual HTTP connection with the service. I call out HTTP specifically, because the only scenario where NetProfileTcpBinding will prove insufficient is if your service is a non-Indigo service and needs to be contacted through HTTP. I will try to comment further on this solution in a future post.

The second thing to note is that your network may not be configured with DNS. Which means that even though machines within your network are all addressable, you may need to identify them by their IP Address. To do this, simply use your machine’s IP Address where you would normally use a hostname (for a Service’s URL or a Proxy’s remote endpoint).

And now back to our (somewhat) regularly scheduled Channels/layering tutorial…