Example of a persistent TCP server using ESP8266Wifi and ESPAsyncTCP

esp8266wifi-async-tcp.ino

#include <ESP8266WiFi.h>
#include <ESPAsyncTCP.h>

#define SERVER_HOST_NAME "esp_server"
#define SSID "YOUR_SSID"
#define PASSWORD "YOUR_SSID_PASSWORD"

#define SERVER_HOST_NAME "esp_server"

#define TCP_PORT 8888

#define MAX_BAUD_RATE 115200
AsyncServer* server = NULL;

/* clients events */
static void handleError(void* arg, AsyncClient* client, int8_t error) {
  Serial.printf("\n connection error %s from client %s \n", client->errorToString(error), client->remoteIP().toString().c_str());
}

static void handleData(void* arg, AsyncClient* client, void* data, size_t len) {
  Serial.printf("\n data received from client %s \n", client->remoteIP().toString().c_str());
  Serial.write((uint8_t*)data, len);

  // reply to client
  if (client->space() > 32 && client->canSend()) {
    char reply[32];
    sprintf(reply, "this is from %s", SERVER_HOST_NAME);
    client->add(reply, strlen(reply));
    client->send();
  }
}

static void handleDisconnect(void* arg, AsyncClient* client) {
  Serial.printf("\n client %s disconnected \n", client->remoteIP().toString().c_str());
}

static void handleTimeOut(void* arg, AsyncClient* client, uint32_t time) {
  Serial.printf("\n client ACK timeout ip: %s \n", client->remoteIP().toString().c_str());
}


/* server events */
static void handleNewClient(void* arg, AsyncClient* client) {
  Serial.printf("\n new client has been connected to server, ip: %s", client->remoteIP().toString().c_str());

  // register events
  client->onData(&handleData, NULL);
  client->onError(&handleError, NULL);
  client->onDisconnect(&handleDisconnect, NULL);
  client->onTimeout(&handleTimeOut, NULL);
}

void setup_wifi() {
  // WiFi parameters
  const char* ssid = SSID;
  const char* password = PASSWORD;

  //Static IP address configuration
  IPAddress staticIP(192, 168, 1, 61);  //ESP static ip
  IPAddress gateway(192, 168, 1, 1);    //IP Address of your WiFi Router (Gateway)
  IPAddress subnet(255, 255, 255, 0);   //Subnet mask
  IPAddress dns(8, 8, 8, 8);            //DNS

  WiFi.disconnect();  // Prevent connecting to wifi based on previous configuration
  ESP.eraseConfig();

  WiFi.config(staticIP, subnet, gateway);
  WiFi.mode(WIFI_STA);  // WiFi mode station (connect to wifi router only
  WiFi.setSleepMode(WIFI_NONE_SLEEP);
  WiFi.begin(ssid, password);

  // Connect to WiFi
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {  // blink to indicate the device is trying to connect to WIFI
    Serial.print(".");
  }
  Serial.println("");
  Serial.println("WiFi connected");

  Serial.println("START MIRRORING SERIAL");
  Serial.println(WiFi.localIP());
}

void setup_serial() {
  Serial.begin(MAX_BAUD_RATE);
}

void setup() {
  setup_serial();
  setup_wifi();

  server = new AsyncServer(TCP_PORT);  // start listening on tcp port 7050
  server->onClient(&handleNewClient, server);
  server->begin();
}

void loop() {
}