Arduino - TCP Client

In this tutorial, we will learn how to program the Arduino Uno R4 WiFi as a TCP Client and exchange data with TCP Server..

Hardware Required

1	×	Arduino UNO R4 WiFi
1	×	USB Cable Type-C
1	×	(Optional) Jumper Wires
1	×	(Recommended) Screw Terminal Block Shield for Arduino UNO R4
1	×	(Recommended) Breadboard Shield For Arduino UNO R4
1	×	(Recommended) Enclosure For Arduino UNO R4
1	×	(Recommended) Power Splitter For Arduino UNO R4

Or you can buy the following sensor kits:

1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	DIYables Sensor Kit (18 sensors/displays)

Disclosure: Some links in this section are Amazon affiliate links. If you make a purchase through these links, we may earn a commission at no extra cost to you.
Additionally, some links direct to products from our own brand, DIYables.

Arduino Code

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-tcp-client */ #include <WiFiS3.h> const char* WIFI_SSID = "YOUR_WIFI_SSID"; // CHANGE TO YOUR WIFI SSID const char* WIFI_PASSWORD = "YOUR_WIFI_PASSWORD"; // CHANGE TO YOUR WIFI PASSWORD const char* TCP_SERVER_ADDR = "192.168.0.26"; // CHANGE TO TCP SERVER'S IP ADDRESS const int TCP_SERVER_PORT = 1470; WiFiClient TCP_client; void setup() { Serial.begin(9600); Serial.println("Arduino: TCP CLIENT"); // check for the WiFi module: if (WiFi.status() == WL_NO_MODULE) { Serial.println("Communication with WiFi module failed!"); // don't continue while (true) ; } String fv = WiFi.firmwareVersion(); if (fv < WIFI_FIRMWARE_LATEST_VERSION) { Serial.println("Please upgrade the firmware"); } Serial.print("Attempting to connect to SSID: "); Serial.println(WIFI_SSID); // attempt to connect to WiFi network: while (WiFi.begin(WIFI_SSID, WIFI_PASSWORD) != WL_CONNECTED) { delay(10000); // wait 10 seconds for connection: } Serial.print("Connected to WiFi "); Serial.println(WIFI_SSID); // connect to TCP server if (TCP_client.connect(TCP_SERVER_ADDR, TCP_SERVER_PORT)) { Serial.println("Connected to TCP server"); TCP_client.write("Hello!"); // send to TCP Server TCP_client.flush(); } else { Serial.println("Failed to connect to TCP server"); } } void loop() { // Read data from server and print them to Serial if (TCP_client.available()) { char c = TCP_client.read(); Serial.print(c); } if (!TCP_client.connected()) { Serial.println("Connection is disconnected"); TCP_client.stop(); // reconnect to TCP server if (TCP_client.connect(TCP_SERVER_ADDR, TCP_SERVER_PORT)) { Serial.println("Reconnected to TCP server"); TCP_client.write("Hello!"); // send to TCP Server TCP_client.flush(); } else { Serial.println("Failed to reconnect to TCP server"); delay(1000); } } }

Quick Step

To do it, follow the below steps:

Connect Arduino to your PC via USB Type-C cable
Install a TCP server software program like ezTerm
Open the TCP server program and configure it as TCP Server, then click Listen button

Open Command Prompt on your PC.
Find the IP address of your PC by running the below command:

ipconfig

The output looks like below:

Command Prompt

C:\WINDOWS\system32>ipconfig Windows IP Configuration Ethernet adapter: Subnet Mask . . . . . . . . . . . : 255.0.0.0 IPv4 Address. . . . . . . . . . . : 192.168.0.26 Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . :

Change the IP address of your TCP Server (Your PC) in the Arduino code. In the example above, it's indicated by 192.168.0.26.
Compile and upload the code to the Arduino board by clicking on the Upload button in the Arduino IDE.
Open the Serial Monitor
You will see the below on Serial Monitor

COM6

Send

Connected to WiFi YOUR_WIFI_SSID Connected to TCP server

Autoscroll Show timestamp

Clear output

9600 baud

Newline

After connecting to TCP server, Arduino will send a "Hello!" to TCP server, and you'll see this text on the TCP server software.

Type some data in the TCP server program to send it to the Arduino through TCP.
If successful, you'll see the data in the Serial Monitor.