Arduino: ESP8266 web server stops responding after some time while sending sensor data

[satyamsanghi1]

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1. Include a Minimal Complete Reproducible Example sketch that shows your issue. Do not include your entire project, or a huge piece of code.
2. Include debug messages:

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Basic Infos

• [ ] This issue complies with the issue POLICY doc.
• [ ] I have read the documentation at readthedocs and the issue is not addressed there.
• [ ] I have tested that the issue is present in current master branch (aka latest git).
• [ ] I have searched the issue tracker for a similar issue.
• [ ] If there is a stack dump, I have decoded it.
• [ ] I have filled out all fields below.

Platform

• Hardware: [ESP-12|ESP-01|ESP-07|ESP8285 device|other]
• Core Version: [latest git hash or date]
• Development Env: [Arduino IDE|Platformio|Make|other]
• Operating System: [Windows|Ubuntu|MacOS]

Settings in IDE

• Module: [Generic ESP8266 Module|Wemos D1 mini r2|Nodemcu|other]
• Flash Mode: [qio|dio|other]
• Flash Size: [4MB/1MB]
• lwip Variant: [v1.4|v2 Lower Memory|Higher Bandwidth]
• Reset Method: [ck|nodemcu]
• Flash Frequency: [40Mhz]
• CPU Frequency: [80Mhz|160MHz]
• Upload Using: [OTA|SERIAL]
• Upload Speed: [115200|other] (serial upload only)

Problem Description

Detailed problem description goes here.

MCVE Sketch

```cpp#include

include

include

include

include

//multiplexing
//int x=D3;
int s0 = D0;
int s1 = D1;
int s2 = D2;
int s3 = D6;
int sig=D5;

//Temperature
dht DHT;
int d=2;

//LIGHT
//analog pin
int ldr=A0;
//D3
int led=0;

//PIR SENSOR
//D8
int pir=15;
//D7
int pirled=13;
String sensordata="";
ESP8266WebServer server(80);

String page="";

void handleClient()
{
String message="";
message+="number of args ";
message+=server.args();
message+=" "+server.argName(0)+" "+server.arg(0);
// server.send(200, "text/plain",message);

if(server.arg(0).equals("on"))
{

digitalWrite(s0,HIGH);
digitalWrite(s1,HIGH);
digitalWrite(s2,HIGH);
digitalWrite(s3, HIGH);
digitalWrite(sig,LOW);
//server.send(200, "text/plain","on");
}
else if(server.arg(0).equals("off"))
{

digitalWrite(s0,LOW);
digitalWrite(s1,LOW);
digitalWrite(s2,LOW);
digitalWrite(s3,LOW);
digitalWrite(sig,LOW);
//server.send(200, "text/plain","off");
}
}
void setup()
{
Serial.begin(9600);
//WiFi.begin("sanghi@19","9165269100@19699");
WiFi.begin("Satyam","hell1234");
delay(50);
while(WiFi.status() != WL_CONNECTED)
{
delay(500);
Serial.println(".");
}

Serial.println("");
Serial.print("Connected to ");
Serial.println("sanghi@19");
Serial.print("IP address: ");
Serial.println(WiFi.localIP());

//LIGHT

pinMode(led,OUTPUT);
pinMode(ldr,INPUT);

//PIR
pinMode(pir,INPUT);
pinMode(pirled,OUTPUT);

//multiplexing
pinMode(s0, OUTPUT);
pinMode(s1, OUTPUT);
pinMode(s2, OUTPUT);
pinMode(s3, OUTPUT);
pinMode(sig,OUTPUT);
digitalWrite(s0, LOW);
digitalWrite(s1, LOW);
digitalWrite(s2, LOW);
digitalWrite(s3, LOW);
digitalWrite(sig,LOW);

if (MDNS.begin("esp8266")) {
Serial.println("MDNS responder started");
}
server.on("/", handleClient);
server.on("/sensordata", {

server.send(200, "text/plain",sensordata);
});

server.begin();
Serial.println("HTTP server started");
delay(3000);
pinMode(s0, OUTPUT);
pinMode(s1, OUTPUT);
pinMode(s2, OUTPUT);
pinMode(s3, OUTPUT);
pinMode(sig,OUTPUT);
digitalWrite(s0, LOW);
digitalWrite(s1, LOW);
digitalWrite(s2, LOW);
digitalWrite(s3, LOW);
digitalWrite(sig,LOW);
}

void loop() {

server.handleClient();
int chk = DHT.read11(d);
// Serial.print("Temperature = ");
// Serial.println(DHT.temperature);
// Serial.print("Humidity = ");
// Serial.println(DHT.humidity);

// sensordata+="
temperature : "+String(DHT.temperature)+" humidity : "+String(DHT.humidity);
sensordata+=",temperature : "+String(DHT.temperature)+" humidity : "+String(DHT.humidity);
// delay(500);
///// LIGHT //////////////////////////////////

// Serial.print("Light Intensity :");
// Serial.println(analogRead(ldr));
int reading=analogRead(ldr);
sensordata+=" Light Intensity : "+String(reading);
if(reading<35)
{
digitalWrite(led,HIGH);
}
else
{
digitalWrite(led,LOW);
}
// delay(500);

//////// PIR SENSOR /////////////////////////////////

String pirstatus;
if(digitalRead(pir)==HIGH)
{
pirstatus=" detected motion";
// Serial.println("detected motion");
digitalWrite(pirled,HIGH);
//delay(50);
}
else{
pirstatus=" motion not detected";
// Serial.println("not detected");
//delay(50);
digitalWrite(pirled,LOW);
}
sensordata+=" PIR value : "+pirstatus;
delay(500);

/////////////////////////////////////////////////
delay(500);

}

[d-a-v]

Your MCVE is not working, sensordata is filling memory, causing an uncaught exception.
Even with this fixed, it still does not work even once. Please test it, update it.
I am currently making requests in a loop running the example ESP8266WebServer>Helloserver and this one works flawlessly.
Please restart your app using this example as a basis.

[devyte]

@BlackBlood007 said (with commented lines removed):

void loop() {

 server.handleClient();
 int chk = DHT.read11(d);
 sensordata+=",temperature : "+String(DHT.temperature)+"  humidity :  "+String(DHT.humidity);
...

sensordata is a String that will keep growing and growing, because it's a global and is never being reset.
Closing due to user error.

[d-a-v]

Also, the unconditional delay(500) in the main loop where server.handleClient() is called is killing the webserver.
There is absolutely no need of any unconditional delay() in the main loop.

[satyamsanghi1]

@BlackBlood007 said (with commented lines removed):

void loop() {

 server.handleClient();
 int chk = DHT.read11(d);
 sensordata+=",temperature : "+String(DHT.temperature)+"  humidity :  "+String(DHT.humidity);
...

sensordata is a String that will keep growing and growing, because it's a global and is never being reset.
Closing due to user error.

@BlackBlood007 said (with commented lines removed):

void loop() {

 server.handleClient();
 int chk = DHT.read11(d);
 sensordata+=",temperature : "+String(DHT.temperature)+"  humidity :  "+String(DHT.humidity);
...

sensordata is a String that will keep growing and growing, because it's a global and is never being reset.
Closing due to user error.
@d-a-v Thank you so much sir for going through my code and making it bug free . After making the changes you told , this works very smoothly .