Yes, I can confirm its working..
in the GatewayESP8266 make sure to change from this:

#if defined(MY_USE_UDP)
  #include <WiFiUdp.h>
#else
  #include <ESP8266WiFi.h>
#endif

to

  #include <WiFiUdp.h>
  #include <ESP8266WiFi.h>

You have to have both libraries instead of just one (wiFiUdp.h)
For case sensitive systems (Linux, OS X) also you have to have the correct upper/lower case in the library name.. it must be:

#include <WiFiUdp.h> 

and NOT:

#include <WiFiUDP.h> 

as in the the example mysensors file.

Scenario: GatewayESP8266 with UDP

If you clone the development version from github and try to compile the GatewayESP8266 with MY_USE_UDP it will fall over a bunch of compilation errors.
The reason is found in the MySensors.h around line 153, GATEWAY - TRANSPORT

#if (defined(MY_CONTROLLER_IP_ADDRESS) || defined(MY_CONTROLLER_URL_ADDRESS))
	#define MY_GATEWAY_CLIENT_MODE
#endif
#if defined(MY_USE_UDP) && !defined(MY_GATEWAY_CLIENT_MODE)
	#error You must specify MY_CONTROLLER_IP_ADDRESS or MY_CONTROLLER_URL_ADDRESS for UDP
#endif

Once you define MY_USE_UDP you will also want to define MY_CONTROLLER_IP_ADDRESS to send the packages to your controller,
However as you see in the first line if MY_CONTROLLER_IP_ADDRESS is defined then MY_GATEWAY_CLIENT_MODE will be auto defined and this
will conflict with UDP use.

I've fixed it changing to:

#if (defined(MY_CONTROLLER_IP_ADDRESS) || defined(MY_CONTROLLER_URL_ADDRESS)) && !defined(MY_USE_UDP)
	#define MY_GATEWAY_CLIENT_MODE
#endif
#if defined(MY_USE_UDP) && (!defined(MY_CONTROLLER_IP_ADDRESS) && !defined(MY_CONTROLLER_URL_ADDRESS))
	#error You must specify MY_CONTROLLER_IP_ADDRESS or MY_CONTROLLER_URL_ADDRESS for UDP
#endif

Scenario: GatewayESP8266 with UDP

If you clone the development version from github and try to compile the GatewayESP8266 with MY_USE_UDP it will fall over a bunch of compilation errors.
The reason is found in the MySensors.h around line 153, GATEWAY - TRANSPORT

#if (defined(MY_CONTROLLER_IP_ADDRESS) || defined(MY_CONTROLLER_URL_ADDRESS))
	#define MY_GATEWAY_CLIENT_MODE
#endif
#if defined(MY_USE_UDP) && !defined(MY_GATEWAY_CLIENT_MODE)
	#error You must specify MY_CONTROLLER_IP_ADDRESS or MY_CONTROLLER_URL_ADDRESS for UDP
#endif

Once you define MY_USE_UDP you will also want to define MY_CONTROLLER_IP_ADDRESS to send the packages to your controller,
However as you see in the first line if MY_CONTROLLER_IP_ADDRESS is defined then MY_GATEWAY_CLIENT_MODE will be auto defined and this
will conflict with UDP use.

I've fixed it changing to:

#if (defined(MY_CONTROLLER_IP_ADDRESS) || defined(MY_CONTROLLER_URL_ADDRESS)) && !defined(MY_USE_UDP)
	#define MY_GATEWAY_CLIENT_MODE
#endif
#if defined(MY_USE_UDP) && (!defined(MY_CONTROLLER_IP_ADDRESS) && !defined(MY_CONTROLLER_URL_ADDRESS))
	#error You must specify MY_CONTROLLER_IP_ADDRESS or MY_CONTROLLER_URL_ADDRESS for UDP
#endif

@Yveaux said:

I recently bumped into PlatformIO.
..
Does not include an editor, but I think this is a good thing as everyone has his own preferred editor, right?
Anyone have experience with it?

You should use Atom editor (IDE) with PlatformIO.
http://docs.platformio.org/en/stable/ide/atom.html
https://atom.io/packages/platformio-ide

Yes, I can confirm its working..
in the GatewayESP8266 make sure to change from this:

#if defined(MY_USE_UDP)
  #include <WiFiUdp.h>
#else
  #include <ESP8266WiFi.h>
#endif

to

  #include <WiFiUdp.h>
  #include <ESP8266WiFi.h>

You have to have both libraries instead of just one (wiFiUdp.h)
For case sensitive systems (Linux, OS X) also you have to have the correct upper/lower case in the library name.. it must be:

#include <WiFiUdp.h> 

and NOT:

#include <WiFiUDP.h> 

as in the the example mysensors file.

I'm trying to compile an Ethernet gateway with support for UDP (MY_USE_UDP) however I can't get it compiled.. I've tried with Arduino IDE 1.6.10 and also in PlatformIO

This library <WiFiUdp.h>, where do I grab it from? Use the one from the ESP8266Wifi arduino core?

Without UDP both Arduino and platformIO get it compiled successful, but it I enable the MY_USE_UDP will fail in:

(MyGatewayTransportEthernet.cpp:46:25: error: 'WiFiClient' does not name a type
  #define EthernetClient WiFiClient

Does anyone have success using UDP in 2.0.0 ?

Thanks.

Hi,
I just installed a fresh version MySensors library (2.0.?) and going through some tests here.
I have a Serial gateway with Nano+nRF24 powered with external +3.3v regulator, with enough juice.
And a node Nano+nRF24+DHT22.

Everything works fine “if” I keep the debug enabled (#define MY_DEBUG) in the gateway.
If I disable debug ( // #define MY_DEBUG) in the gateway then I get an error in the Node:

TSM:INIT
TSM:RADIO:OK
TSP:ASSIGNID:OK (ID=4)
TSM:FPAR
TSP:MSG:SEND 4-4-255-255 s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=bc:
TSP:MSG:READ 0-0-4 s=255,c=3,t=8,pt=1,l=1,sg=0:0
TSP:MSG:FPAR RES (ID=0, dist=0)
TSP:MSG:PAR OK (ID=0, dist=1)
TSM:FPAR:OK
TSM:ID
TSM:CHKID:OK (ID=4)
TSM:UPL
TSP:PING:SEND (dest=0)
!TSP:MSG:SEND 4-4-0-0 s=255,c=3,t=24,pt=1,l=1,sg=0,ft=0,st=fail:1
TSP:CHKUPL:FAIL (hops=255)
!TSM:UPL:FAIL

As i said before, the weird thing is that if debug enabled in the gateway, it works.
How can I start troubleshooting this issue?

Thanks.