ESP8266 WiFi Module Tutorial 3 - WiFi Station Mode and TCP Client

In the previous tutorial, we have seen how to setup the ESP-01 module as an access point and running a TCP server on it. In this tutorial, I will explain how to setup the ESP module as a station (WiFi device) and connects to an existing access point. The ESP module is configured as a TCP client, so it can connect to any TCP server. This is the block diagram that explain the system in this tutorial.

In this system, I will setup a PC as a WiFi soft access point (using Connectify software). The PC also runs a TCP server on port 23 using Hercules TCP terminal. The ESP module which acts as a WiFi station can connect to the PC access point. The ESP module which also acts as a TCP client can make a connection to the TCP server on the PC. After the connection is created, we can exchange data with the server. Serial to USB converter and serial terminal (Hercules) is used for controlling the ESP module.

First, you must setup a PC as a soft access point using Connectify software. This software will turn the PC as a soft AP. After that, start TCP server (port 23) on the PC using Hercules TCP terminal.

We need to setup ESP module as station mode, so we send this command: AT+CWMODE=1. You can check the previous tutorial for the detail explanation about ESP mode. After you set the mode, you can check available WiFi AP using this command: AT+CWLAP.

You can join to an existing AP using "AT+CWJAP" command. This is the detail explanation of this command.

You can join to Connectify AP by sending this command: AT+CWJAP="Connectify","12345678". If this connection is successful, then ESP will return this response:

You can check the IP address of the ESP module using this command: AT+CIFSR.

To make sure the connection is successfully connected, we can try to ping between ESP module to PC. To ping from ESP module, we can use this command AT+PING="192.168.82.1". To ping from PC, we can use command line interface.

Up to this point, ESP module and PC is connected in one network, but we still have to setup the TCP connection. To connect to the TCP server, we can use "AT+CIPSTART" command.

To connect to the TCP server, we must know the IP address of the PC. We can get the PC IP address by using "ipconfig" command from Windows command line interface. After we know the I address, we can connect to a TCP server by this command: AT+CIPSTART="TCP","192.168.82.1",23. If the connection is successful, ESP module will return this response.

To send a data from the ESP module to the PC, we can use "AT+CIPSEND" command. After execute this command, you can type the data to be sent on the serial terminal. This is the detail explanation of this command.

For example, if you want to send this message: This message is from ESP8266 TCP client. from TCP client (ESP module) to TCP server (PC), you can send this command: AT+CIPSEND=40. "40" is the number of characters of the message.

The data that we have sent from ESP module as a TCP client will be displayed on TCP server. This is the received message on TCP server.

On the TCP server application we can also send a data to ESP module. The data received from TCP server will be in this format:

"35" is the number of received characters.

As in the previous tutorial, this tutorial is also explain how to setup ESP module manually using serial to USB converter and serial terminal software. If you want to make a useful project, you need to use a microcontroller to control the ESP. This tutorial will be useful for debugging purpose when you encounter a error when using a microcontroller

If you have a WiFi router, you can try another scenario such as ESP module as station (connected to the WiFi router), but runs as a TCP server instead of TCP client.