added basic linux tutorial

docs/walkthrough.md

@@ -0,0 +1,38 @@
+Walkthrough
+======
+
+In this document we'll run through a simple example which should demonstrate the concept of the ZeroTierSDK. For this tutorial you'll need two devices (or at least the ability to run a VM or something like Docker).
+
+### Create your virtual network
+ - Download ZeroTier at (zerotier.com)[https://www.zerotier.com/]
+ - Install it on a device/computer
+ - Create an account and new virtual network at (my.zerotier.com)[https://my.zerotier.com/]
+ - Join your device to the network and assign it an address `zerotier-cli join <nwid>`
+ - Use `zerotier-cli listnetworks` to verify that you've joined the network.
+
+### On your second device, Build the SDK
+ - On Linux: `make linux SDK_PICOTCP=1 SDK_IPV4=1 SDK_DEBUG=1; make -s check; ls -lG build`
+
+### Build test apps
+
+```
+make tests
+```
+
+### Start the SDK service
+```
+./zerotier-cli -U -p8000 /network/homepath &
+```
+
+### Set environment variables 
+```
+export ZT_NC_NETWORK=/network/homepath/nc_XXXXXXXXXXXXXXXX
+export LD_PRELOAD=./libztintercept.so
+```
+
+### Start your app
+```
+./build/tests/linux.tcpserver4.out 8001
+```
+
+*Now, you'll note that your new TCP server is automatically intercepted and available at on port 80001*