Serial interface is common requirement for most of the application development. We are discussing on how to do 3.3V to 5V level conversion for converting serial TTL to RS232 level from 3.3V you can use MAX3232 it operates at 3.3V levels.
On ESP8266 we have one hardware serial i.e. GPIO2 (Tx) and GPIO3 (Rx).
Hardware Serial Programming is similar to the Arduino Serial. Remember that few USB to Serial converter does not support higher baud rate. It is better to keep baud rate below 115200. Continue reading ESP8266 Serial Communication