NodeMCU stops responding after several hours

Question

I'm controlling some devices through a relay and a NodeMCU, it works fine and reconnects without problem in the meantime I'm testing it, but after I leave it like for 3 or more hours, it stops responding. I need this system to always be working without sleeping or anything. Here is my code:

#include <ESP8266WiFi.h>

const char* ssid = "wifi_Guerrero ";
const char* password = "3245968530";

int ledPin = 13; // GPIO13
int ledPin2 = 12; // GPIO13
int desconectado = 5;
int conectado = 4;
WiFiServer server(80);
WiFiClient client;

int counter = 0;

void setup() {
  Serial.begin(9600);
  delay(10);

  pinMode(ledPin, OUTPUT);
  digitalWrite(ledPin, LOW);

  pinMode(ledPin2, OUTPUT);
  digitalWrite(ledPin2, LOW);

  pinMode(conectado, OUTPUT);
  pinMode(desconectado, OUTPUT);
  digitalWrite(desconectado, HIGH);

  connectWifi();  

  Serial.print(F("Setting static ip to : "));
  Serial.println(WiFi.localIP());    

  // Start the server
  server.begin();
  Serial.println("Server started");



}

void loop() {

  delay(200);

  if (WiFi.status() != WL_CONNECTED) {
    delay(100);
    digitalWrite(conectado, LOW);
    digitalWrite(desconectado, HIGH);
   connectWifi(); 
  }

  // Check if a client has connected
  client = server.available();
  if (!client) {
    return;
  }

  // Wait until the client sends some data
  Serial.println("new client");
  int t = millis();
  while(!client.available()){
  delay(1);
  if (millis()-t>130) return;
  }

  // Read the first line of the request
  String request = client.readStringUntil('\r');
  Serial.println(request);
  client.flush();

  // Match the request
  if (request.indexOf("/switch") != -1)  {
    digitalWrite(ledPin, !digitalRead(ledPin));
    digitalWrite(ledPin2, !digitalRead(ledPin2));
    printSwitch();
  }else if (request.indexOf("/uno") != -1) {
    client.print("Canal 1 apagagado | Canal 2 encendido");
    digitalWrite(ledPin, HIGH);
    digitalWrite(ledPin2, LOW);
  }else if (request.indexOf("/dos") != -1){
    client.print("Canal 1 encendido | Canal 2 apagado");
    digitalWrite(ledPin, LOW);
    digitalWrite(ledPin2, HIGH);
  }else if (request.indexOf("/tres") != -1){
    client.print("Canal 1 apagado | Canal 2 apagado");
    digitalWrite(ledPin, HIGH);
    digitalWrite(ledPin2, HIGH);
  }else if (request.indexOf("/cuatro") != -1){
    client.print("Canal 1 encendido | Canal 2 encendido");
    digitalWrite(ledPin, LOW);
    digitalWrite(ledPin2, LOW);
  }else if (request.indexOf("/cinco") != -1){
    printIP();
  }else if (request.indexOf("/apagaruno") != -1){
    client.print("Canal 1 apagado");
    digitalWrite(ledPin, HIGH);
  }else if (request.indexOf("/apagardos") != -1){
    client.print("Canal 2 apagado");    
    digitalWrite(ledPin2, HIGH);
  }else if (request.indexOf("/prenderuno") != -1){
    client.print("Canal 1 encendido");
    digitalWrite(ledPin, LOW);
  }else if (request.indexOf("/prenderdos") != -1){
    client.print("Canal 2 encendido");
    digitalWrite(ledPin2, LOW);
  }else if (request.indexOf("/canaluno") != -1){

    if(digitalRead(ledPin) == HIGH) {    
      client.print("Off");
  } else {
    client.print("On");    
  }

  }else if (request.indexOf("/canaldos") != -1){

    if(digitalRead(ledPin2) == HIGH) {    
    client.print("Off");
  } else {
    client.print("On");
  }

  }

// Set ledPin according to the request
//digitalWrite(ledPin, value);

  // Return the response  

  delay(1);
  Serial.println("Client disonnected");
  Serial.println("");

}

void printSwitch(){ 
  if(digitalRead(ledPin) == LOW) {
    client.print("Canal 1 Encendido");
  } else {
    client.print("Canal 1 Apagado");
  }
  Serial.println("");
  if(digitalRead(ledPin2) == LOW) {
    client.print("Canal 2 Encendido");
  } else {
    client.print("Canal 2 Apagado");
  }
}

void printIP(){
  delay(100); 
  client.print(WiFi.localIP());
}

void connectWifi()
{
  Serial.print("Connecting to "+*ssid);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
  delay(500);
  Serial.print(".");
  }  

  // config static IP
  IPAddress ip(192, 168, 0, 8);
  IPAddress gateway(192, 168, 0, 1);
  IPAddress subnet(255, 255, 255, 0);  
  WiFi.config(ip, gateway, subnet);
  digitalWrite(conectado, HIGH);
  digitalWrite(desconectado, LOW);
  Serial.println("");
  Serial.println("Connected");
  Serial.println("");  

  // Print the IP address
  Serial.print("Use this URL to connect: ");
  Serial.print("http://");
  Serial.print(WiFi.localIP());
  Serial.println("/");
}//end connect

Answer 1

I think thatthe problem lies with this definition

String request = client.readStringUntil('\r');

which you define dynamically in loop this leads possibly to heap fragmentation, causing resets after sometime
Define a global char array

char request [256] ={'\0'};
char c;
uint cc = 0;

and work instead the String functions with

while(client.available()){      
c = client.read();    
if (c != '\r'){ 
  request[cc] = c;
   cc++;
 }
 else return;
}

then handle the filled request buffer like

if (strcmp(request,"/switch") != 0)  {
  ....
 }

This should keep you esp running