Connect to attached pc from WP7 by opening a socket to localhost

When developing and testing WP7 apps you're pc is connected to either a real WP7 phone or to the WP7 Device Emulator. For a specific development-purpose I would like to connect directly to the development pc (let's call it the host pc) from the WP7 app without having to rely on an external toast-server. I'm using plain sockets, System.Net.Sockets.Socket.

There seem to be two options:

1. Obtain the host pc's LAN IP and connect to that
2. Connect to localhost

Option 1 usually works well, but not always: The host pc may not necessaily have an IP, in which case there's nothing to connect to. Also, in some scenarios all LAN traffic is directed through a company-wide proxy which will disrupt this mechanism.

That lead me to try out option 2. To my surprise it seems to work, but I need to be more sure than simply "it seems to work". I've googled all over but can't find any definitive answer, not even on Microsoft's site like e.g. http://msdn.microsoft.com/en-us/library/ff754351(v=VS.92).aspx. So this is my question:

What exactly is the defined behavior of connecting to localhost from a WP7 app?

Altrernatively, is there a fool-proof way of connecting back to the host-pc?

(Let me stress this again: For this particular purpose I can't use toasts, because the development pc may not even be online.)

Edit: I work at EQATEC and the开发者_运维百科 application in question is the EQATEC Profiler. Right now the profiler/app-communication is handled by injecting a socket/http-client into the deployed WP7 app that connects back to the profiler's LAN IP address. It works very well and is really fast, but in some very rare cases users are offline and therefore doesn't have an IP, or have some prohibitive lan proxy rules.

Therefore connecting to "localhost" would be excellent if that somehow magically would always work for everybody. It works for me and a couple of test-users, but does it work for all our many thousand profiler users all over the world? I'd like to be more sure.

"localhost" by definition is the machine running the code (well specifically the NIC doing the communication). For either the Phone or the Emulator, that would mean the phone or the emulator, not the PC they are attached to.

When you attach to a PC, you do have a network - it's an RNDIS connection in which both sides get an IP address which traditionally (pre-WP7) could be resolved with 'ppp-peer', though I've not tested that resolution on the Phone. I suspect it will be the same, since WMDC is still what's connecting and they'd have little reason to change that connection mechanism.

If the emulator is resolving localhost to the PC on which is resides, that's a definite bug and I would not count on it continuing to work as they add more robust socket support to the Phone platform.

System.Net.Sockets.Socket isn't really currently available for WP7 programming, but it might be available at some future point (maybe in Mango... maybe...)

AFAIK, the only way to reliably do what you want to do is to set up an http server on the development PC and to provide your app with an HTTP address of that server - or to route messages via some "Cloud proxy"

I'm surprised localhost works at all on the real device... I can only assume that they are asking the connected PC to resolve that DNS name - but even then I'm surprised 127.0.0.1 works.

The ip you're looking for is "192.168.55.100"

That's the ip address the phone uses to connect to the host pc.

If you'd like to connect to the phone, apparently its ip address will be "192.168.55.101"

For the emulator just use localhost or 127.0.0.1

This is from the old ActiveSync days, so I don't know how official it is or how likely it is to last, but for right now at least it worked on my phone.