ESP8266 Serial

 Serial.swap();
 // Hardware serial is now on RX:GPIO13 TX:GPIO15
 // use SoftwareSerial on regular RX(3)/TX(1) for logging
 logger = new SoftwareSerial(3, 1);

• http://arduino.esp8266.com/Arduino/versions/2.1.0-rc2/doc/reference.html

UART0

U0_TXD = IO1
U0_RXD = IO3
can be remapped to GPIO15 (TX) and GPIO13 (RX) 

UART1

U1_TXD = IO2