How can I achieve serial communication between 4 esp8266,just to transfer some sensor data to one another,without using the router.please help me if someone know about this.
RS-485 might be used but that's hard to tell because the specification is almost non-existing.
How is the data formatted? Is the data simply spread to all other devices or is there a kind of hierarchy? Should there be a bus between them? Why is using the WiFi connection not an option? What distance do you have between the different ESP8266? How is the MQTT mentioned in the subject involved? You see, questions over questions.
You can try creating software UART ports for your ESPs.
I have the same scenario but I have to send sensor data to application having 3 different esp8266-01 the range between these are quiet far please help the both of us