A high-performance, non-blocking Telnet server library specifically designed for the ESP32 using the Arduino framework.

By leveraging the AsyncTCP stack, this library operates entirely through event-driven callbacks. This ensures your main loop() remains unblocked, providing maximum stability for time-critical applications such as sensor polling, display updates, or motor control.

• Fully Asynchronous: No polling or loop() overhead; events are handled via background tasks.
• Flash Optimized: Minimal binary footprint.
• Single-Client Lock: Automatically manages connection attempts to ensure stable logging.
• Robust Memory Management: Implements active protection against dangling pointers and network-related crashes.

This library requires the following asynchronous TCP stack depending on your platform:

• ESP32: AsyncTCP

Include the header and instantiate the server. The default port is 23.

#include "AsyncTelnet.h"

// Initialize server on default port 23
AsyncTelnet logsrv;

void onTelnetConnect(void* arg, AsyncClient* client) {
    Serial.println("Telnet: Client connected.");
}

#if HANDLE_INCOMMING_DATA
void onTelnetData(const char* data) {
    Serial.printf("Telnet Input: %s\n", data);
}
#endif

Start the server in your setup() function.

void setup() {
    Serial.begin(115200);
    // Standard WiFi initialization...

    logsrv.onConnect(onTelnetConnect);

    #if HANDLE_INCOMMING_DATA
    logsrv.onIncomingData(onTelnetData);
    #endif

    if (logsrv.begin()) {
        Serial.println("Telnet Server active.");
    }
}