Background: I know nothing about hardware.

I am writing a small project with Arduino IDE, ESP8266 library, and my board is ESP8266 V3 ESP-12N F NodeMcu Lua CP2102.

Now I get Exception 29 and I don't know why.

Sketch and server code(written in Python) github link (I also posted the client and server code at the bottom)

Stack Dump:

Exception 29: StoreProhibited: A store referenced a page mapped with an attribute that does not permit stores
PC: 0x4000e1c3
EXCVADDR: 0x00000018

Decoding stack results
0x40100908: malloc(size_t) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\umm_malloc\umm_malloc.cpp line 511
0x40100b6e: calloc(size_t, size_t) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\umm_malloc\umm_malloc.cpp line 826
0x40100b60: calloc(size_t, size_t) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\umm_malloc\umm_malloc.cpp line 820
0x4020318b: loop_task(ETSEvent*) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\core_esp8266_main.cpp line 188
0x40100154: ets_post(uint8, ETSSignal, ETSParam) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\core_esp8266_main.cpp line 160
0x40100154: ets_post(uint8, ETSSignal, ETSParam) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\core_esp8266_main.cpp line 160
0x40100154: ets_post(uint8, ETSSignal, ETSParam) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\core_esp8266_main.cpp line 160
0x40100154: ets_post(uint8, ETSSignal, ETSParam) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\core_esp8266_main.cpp line 160
0x40100154: ets_post(uint8, ETSSignal, ETSParam) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\core_esp8266_main.cpp line 160
0x40100154: ets_post(uint8, ETSSignal, ETSParam) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\core_esp8266_main.cpp line 160
0x40100154: ets_post(uint8, ETSSignal, ETSParam) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\core_esp8266_main.cpp line 160
0x40100154: ets_post(uint8, ETSSignal, ETSParam) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\core_esp8266_main.cpp line 160
0x40100154: ets_post(uint8, ETSSignal, ETSParam) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\core_esp8266_main.cpp line 160
0x40100154: ets_post(uint8, ETSSignal, ETSParam) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\core_esp8266_main.cpp line 160
0x402109ff: tcp_output at core/tcp_out.c line 1259
0x4020216a: ClientContext::wait_until_sent(int) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\libraries\ESP8266WiFi\src/include/ClientContext.h line 331
0x40100908: malloc(size_t) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\umm_malloc\umm_malloc.cpp line 511
0x402151c0: mem_malloc at core/mem.c line 210
0x4020f104: pbuf_alloc_LWIP2 at core/pbuf.c line 284
0x40214732: ip4_output_if at core/ipv4/ip4.c line 1550
0x4020fe90: tcp_write at core/tcp_out.c line 263
0x402031dc: __esp_yield() at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\core_esp8266_main.cpp line 100
0x4020378e: __delay(unsigned long) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\core_esp8266_wiring.cpp line 54
0x4020230f: ClientContext::_write_from_source(DataSource*) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\libraries\ESP8266WiFi\src/include/ClientContext.h line 464
0x4020239d: WiFiClient::write(unsigned char const*, unsigned int) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\libraries\ESP8266WiFi\src/include/ClientContext.h line 364
0x40204c30: WiFiClient::write(unsigned char) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\libraries\ESP8266WiFi\src\WiFiClient.cpp line 217
0x40201bc4: DataSource::~DataSource() at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\libraries\ESP8266WiFi\src/include/DataSource.h line 12
0x402026c9: WiFiClient::flush(unsigned int) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\libraries\ESP8266WiFi\src\WiFiClient.cpp line 318
0x40201113: loop() at C:\Users\ptq00\Documents\Arduino\sketch_jan03b/sketch_jan03b.ino line 44
0x40100154: ets_post(uint8, ETSSignal, ETSParam) at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\core_esp8266_main.cpp line 160
0x402032f4: loop_wrapper() at C:\Users\ptq00\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266\core_esp8266_main.cpp line 180

Sketch(Client) Code:

#include <ESP8266WiFi.h>

const char ssid[] = "luminous";
const char pass[] = "zxcv78()[]";

//Mac IP 192.168.1.101 
//PC IP 192.168.1.103

IPAddress server(192,168,0,103);
int port = 12700;

WiFiClient client;

void setup() {
  // put your setup code here, to run once:
  
  Serial.begin(115200);
  Serial.println("");
  
  WiFi.begin(ssid, pass);
  delay(500);
  while(WiFi.status() != WL_CONNECTED){
    delay(500);
    Serial.print(".../");  
  }

  Serial.println("");
  //WiFi is connected
 
  if(client.connect(server, port)){
    Serial.println("connected to server");
  }

}

// 3s client read timeout. I set this value casually. The server has a 5s timeout when reading data from client.
const unsigned long clientTimeout = 3000; 
                                              
void loop() {
  // put your main code here, to run repeatedly:

  if(client.connected()){
    client.write(WiFi.RSSI());
    delay(100); // Add for nothing. Not sure if it's useful
    unsigned long timeout = millis();
    //Client timeout, if client can't reach the server, it should start to reconnect the server
    while(client.available() == 0){
      if (millis() - timeout >= clientTimeout){
        Serial.println(">>> Client Timetout !");
        client.stop();
        break;
      }
    }
    //Client is connected and has data to read
    //discard all data
    client.flush();
  }else{
    //Try to reconnect to the server
    client.connect(server,port);
    delay(500); // Add for nothing. Not sure if it's useful
    while(!client.connected()){
       //failed to reconnect
       Serial.println("Failed to reconnect...");
       delay(500);
       client.connect(server,port);
    }
    //succeed reconnecting
    Serial.println("Succeeded reconnecting..");
  }
}

Server Code:

import socket


HOST = '0.0.0.0'
PORT = 12700

catSafeZone = False
serverTimeout = 3

with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1);
    s.bind((HOST, PORT))
    s.listen()
    print("Start listening")
    print("Device is not conncted")

    while True:
        conn, addr = s.accept()
        try:
            with conn:
                print("Connected by", addr)
                print("Cat is online")
                conn.settimeout(serverTimeout)

                # client won't try to disconnect on its own.
                # So we only need to capture connection timeout exception
                while True:
                    data = conn.recv(128)
                    if data:
                        if catSafeZone == False:
                            catSafeZone = True
                            print("Cat is in safe zone.")
                        conn.send(b'1')
                    else:
                        print("Unexpected condition")
                        print("Client disconnected on its own.")
                        raise Exception("server data NULL")

                    # Code that is used for wifi signal strength detection:
                    #
                    # if not data:
                    #     break
                    # wifiStrength = int.from_bytes(data, byteorder='big', signed=True)
                    # print(wifiStrength)

        except socket.timeout:
            print("!!!Cat is out of safe zone")
            # Warn user in some ways
            catSafeArea = False



# never reach here
print("Server shutdown")