Note that what's really going on in this thread is the difference between setting up a private network vs. "bridging" to the outside (next up enclosing) network. Generally, when setting up virtual machines (regardless of which emulator software you are using), you have a choice between setting up the virtual machine on its own private network vs. bridging out to (usually) your home LAN. In the former case, you (usually) end up with an IP address like 10.x.y.z; in the later, you (usually) end up with an IP address like 192.168.x.y.
The basic difference is that with a private network, you can go out, but they can't come in. That's how your home LAN is setup - so that you can go out to the Internet, but they (the bad guys) can't come in. So, in this instance, when you tell QEMU to setup a 10.x.y.z network, you are setting up a network that, without special "hacks" (e.g., the "-redir" command line option), you can't get into it in from outside.
The easiest (though, perhaps not best) solution is to do whatever is needed to setup the QEMU emulated machine with a "bridged" network - which should get it on IP address in the 192.168.x.y range, and will be directly accessible from the other machines on your LAN.
And some folks need to stop being fanboys and see the forest behind the trees.
(One of the best lines I've seen on this board lately)