This library is no longer maintained and has been superseded.

Please use the new SerialNetworkBridge library for all future projects and updates.

SerialTCPClient has been replaced by SerialNetworkBridge. The new library offers improved performance, better architecture, and continued support.

If you are currently using SerialTCPClient, we highly recommend migrating your project to SerialNetworkBridge. The documentation below is kept for legacy reference only.

Bring secure TCP/UDP networking to any Arduino board via a simple serial bridge.

SerialTCPClient provides a simple way to use TCP or UDP client functionality over a serial link, enabling boards without native networking to communicate through a WiFi‑capable device.

It is designed for Arduino boards such as AVR, STM32, and Teensy that lack built‑in WiFi or Ethernet, offering a straightforward alternative to firmware‑based solutions available only on certain boards. By bridging communication through modules like ESP32, ESP8266, Raspberry Pi Pico W, or MKR WiFi 1010, the library makes network access broadly available. With support for SSL/TLS and protocol upgrades, SerialTCPClient enables secure communication without requiring firmware‑level certificate management, making it a practical and flexible option for embedded developers.

• Bridge TCP and UDP client communication via serial interface.
• Designed for Arduino boards that lack built‑in WiFi/Ethernet.
• Compatible with WiFi‑capable modules (ESP32/ESP8266/Raspberry Pi Pico W, MKR WiFi 1010, etc) acting as a network bridge.
• Lightweight, header‑only design for embedded use.
• Support for SSL/TLS (HTTPS) and STARTTLS upgrades.
• Example sketches included for quick start.

You can install SerialTCPClient directly from the Library Manager:

1. Open Arduino IDE.
2. Go to Sketch → Include Library → Manage Libraries… 3. Search for SerialTCPClient.
3. Click Install.

Add SerialTCPClient via the PlatformIO Library Registry:

1. Open your project’s platformio.ini.
2. Add the library under lib_deps:

lib_deps = mobizt/SerialTCPClient

3. Build your project — PlatformIO will automatically fetch and install the library.

• Arduino AVR boards (e.g., Uno, Mega2560)
• ESP32 / ESP8266 (as WiFi bridge)
• Raspberry Pi Pico W
• STM32 series
• Teensy boards
• MKR WiFi 1010, MKR 1000 WiFi, Arduino UNO WiFi Rev2
• Other boards with HardwareSerial support

Most Arduino AVR boards (Uno, Mega) operate at 5V, while ESP32/ESP8266 modules operate at 3.3V.

• Arduino TX (5V) → ESP32 RX (3.3V): You MUST use a logic level converter or a voltage divider (e.g., 10kΩ + 20kΩ resistors) to step down 5V to 3.3V. Connecting 5V directly to an ESP32 RX pin may damage it.
• ESP32 TX (3.3V) → Arduino RX (5V): This is usually safe directly, as 3.3V is high enough to be read as HIGH by 5V logic.

The following benchmarks were collected running the Basic HTTP GET example with ENABLE_SERIALTCP_DEBUG disabled.

*Teensy 4.1 RAM usage combines RAM1 and RAM2 variables.

#define ENABLE_SERIALTCP_DEBUG // For debugging
#include <SerialTCPClient.h>

SerialTCPClient client(Serial2, 0 /* slot */); // Corresponding to Network client 
                                               // or SSL client slot 0 on the host

void setup()
{
  Serial.begin(115200);

  // The baud rate should be matched the host baud rate.
  Serial2.begin(115200, SERIAL_8N1, 16, 17);

  client.setLocalDebugLevel(1); // 0=None, 1=Enable

  if (client.connect("example.com", 443))
  {
    client.print("GET / HTTP/1.1\r\n");
    client.print("Host: example.com\r\n");
    client.print("Connection: close\r\n\r\n");

    while (client.available() == 0)
      delay(0);

    while (client.available())
    {
      int b = client.read();
      if (b >= 0)
      {
        Serial.print((char)b);
      }
    }

    client.stop();
  }
}

void loop()
{
}

This library is released under the MIT License.
See LICENSE for details.

Pull requests are welcome!
Please open an issue first to discuss proposed changes or enhancements.

Developed and maintained by mobizt.