This works fine with the current install of the ESP8266 for Arduino libraries
Just set your own router SSID and Password, and run using Jinx software available from http://www.live-leds.de/
This forms the basis of a few projects I am running using multiple universes and browser-based configuration
/*
SmartShow AirPixel ONE - Single Universe ArtNet to WS2812 Driver - For Wemos D1
You can set the Device IP, and universe number below
Works perfectly with Jinx LED software
*/
#include <ESP8266WiFi.h>
#include <WiFiUdp.h>
#define WSout 5 // Pin D1
#define WSbit (1<<WSout)
// ARTNET CODES
#define ARTNET_DATA 0x50
#define ARTNET_POLL 0x20
#define ARTNET_POLL_REPLY 0x21
#define ARTNET_PORT 6454
#define ARTNET_HEADER 17
WiFiUDP udp;
uint8_t uniData[514];
uint16_t uniSize;
uint8_t hData[ARTNET_HEADER + 1];
uint8_t net = 0;
uint8_t universe = 0;
uint8_t subnet = 0;
const char* ssid = "RouterSSID";
const char* password = "RouterPASS";
IPAddress local_ip(192, 168, 1, 200);
IPAddress gateway_ip(192, 168, 1, 1);
IPAddress subnet_ip(255, 255, 255, 0);
void setup() {
Serial.begin(115200);
delay(10);
Serial.println();
Serial.println();
Serial.print("Connecting to ");
Serial.println(ssid);
WiFi.begin(ssid, password);
WiFi.config(local_ip, gateway_ip, subnet_ip);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
udp.begin(ARTNET_PORT); // Open ArtNet port
Serial.println("");
Serial.println("WiFi connected");
Serial.println("IP address: ");
Serial.println(WiFi.localIP());
pinMode(WSout, OUTPUT);
}
void ICACHE_FLASH_ATTR sendWS() {
uint32_t writeBits;
uint8_t bitMask, time;
os_intr_lock();
for (uint16_t t = 0; t < uniSize; t++) { // outer loop counting bytes
bitMask = 0x80;
while (bitMask) {
// time=0ns : start by setting bit on
time = 4;
while (time--) {
WRITE_PERI_REG( 0x60000304, WSbit ); // do ON bits // T=0
}
if ( uniData[t] & bitMask ) {
writeBits = 0; // if this is a '1' keep the on time on for longer, so dont write an off bit
}
else {
writeBits = WSbit; // else it must be a zero, so write the off bit !
}
time = 4;
while (time--) {
WRITE_PERI_REG( 0x60000308, writeBits ); // do OFF bits // T='0' time 350ns
}
time = 6;
while (time--) {
WRITE_PERI_REG( 0x60000308, WSbit ); // switch all bits off T='1' time 700ns
}
// end of bite write time=1250ns
bitMask >>= 1;
}
}
os_intr_unlock();
}
void loop() {
if (udp.parsePacket()) {
udp.read(hData, ARTNET_HEADER + 1);
if ( hData[0] == 'A' && hData[1] == 'r' && hData[2] == 't' && hData[3] == '-' && hData[4] == 'N' && hData[5] == 'e' && hData[6] == 't') {
if ( hData[8] == 0x00 && hData[9] == ARTNET_DATA && hData[15] == net ) {
if ( hData[14] == (subnet << 4) + universe ) { // UNIVERSE
uniSize = (hData[16] << 8) + (hData[17]);
udp.read(uniData, uniSize);
//Serial.print("ArtNet packet RX Uni 0 - size:");
//Serial.println(uniSize);
sendWS();
}
} // if Artnet Data
}
}
}
... The first one which do not flicker leds. But I'm totally newbie in arduino coding 
I'm total newbie in arduino and when I paste your code into .ino in place of orginal one this give me error