WiFiServer hangs after 24+ hours

Official Hardware UNO Family UNO WiFi Rev2
1

I am running WiFiServer & WiFiClient on a Arduino WiFi Rev2. After a day or more, the web server becomes unresponsive, causing an ERR_EMPTY_RESPONSE on my Chrome browser. Tracing the Ethernet traffic, I can see that Arduino accepts the tcp connection, and acknowledges my "GET /" http request, but immediately after this closes the tcp connection with a FIN packet.

Anybody out there also having stability problems with WiFiServer ?

I initially thought that the USB connection would provide a good debug backdoor to my Arduino, but when I plug-in a USB cable to my hanging Arduino and connect it to the web-based Arduino Editor, the Arduino is reset when I start the Monitor. Also Monitor data is often garbled (suspect bad USB driver on pc, since garbling requires a pc reboot to be fixed).

Does anybody have an idea how I can establish a backdoor to my hanging Arduino, to tweak out some data from it ?

#include "DHT.h"
#include <WiFiNINA.h>

#define DHTPIN 2     // Digital pin connected to the DHT sensor
#define DHTTYPE DHT22   // DHT 22  (AM2302), AM2321
DHT dht(2, DHT22);

char ssid[] = "home_network";             //  your network SSID (name) between the " "
char pass[] = "password";      // your network password between the " "
int status = WL_IDLE_STATUS;      //connection status
WiFiServer server(80);            //server socket
WiFiClient client = server.available();

int ledPin = 2;
int statHttpRequests = 0;
int statSensorOk = 0;
int statSensorZero = 0;
int statSensorError = 0;
int statWifiReconnects = 0;
long unsigned statLoopCnt = 0;
long unsigned statLoopCntHigh = 0;
long unsigned watchdogCnt = 0;

void resetFunc() { asm volatile ("jmp 0"); }

void printStatus() {
  client.print("<br>http_request ");
  client.print(statHttpRequests);
  client.print("<br>sensor_ok ");
  client.println(statSensorOk);
  client.print("<br>sensor_zero ");
  client.println(statSensorZero);
  client.print("<br>sensor_err ");
  client.println(statSensorError);
  client.print("<br>wifi_rssi ");
  client.print(WiFi.RSSI());
  client.print("dBm<br>");
  client.print("wifi_reconnects ");
  client.print(statWifiReconnects);
  client.print("<br>statLoopCnt ");
  client.print(statLoopCnt);
}

void printHumTemp() {
  // Reading temperature or humidity takes about 250 milliseconds!
  // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
  float h = dht.readHumidity();
  float t = dht.readTemperature();
  
  // Check if any reads failed and exit early (to try again).
  if (isnan(h) || isnan(t)) {
    statSensorError++;
    client.println("sensor1 ?? ??");
    // The 'F' macro moves the constant string from the 6KB ram to the 48KB flash 
    Serial.println(F("Warning: failed to read from DHT sensor"));
    return;
  } else if (h == 0.0 || t == 0.0) {
    statSensorZero++;
  } else {
    statSensorOk++;
  }

  // Rendering of html removes multiple spaces.
  client.print("sensor1 ");
  client.print(h, 1);
  client.print("%RH ");
  client.print(t, 1);
  client.println("degC<br>");
  
}

void printWifiStatus() {
  // print the SSID of the network you're attached to:
  Serial.print("SSID: ");
  Serial.println(WiFi.SSID());

  // print your board's IP address:
  IPAddress ip = WiFi.localIP();
  Serial.print("IP Address: ");
  Serial.println(ip);

  // print the received signal strength:
  long rssi = WiFi.RSSI();
  Serial.print("signal strength (RSSI):");
  Serial.print(rssi);
  Serial.println(" dBm");

  Serial.print("To see this page in action, open a browser to http://");
  Serial.println(ip);
}

void webWifiStatus () {
  // same as 'printWifiStatus' but as a web line
  client.print("SSID ");
  client.println(WiFi.SSID());

  long rssi = WiFi.RSSI();
  client.print("RSSI ");
  client.print(rssi);
  client.println(" dBm");
}

void enable_WiFi() {
  // check for the WiFi module:
  if (WiFi.status() == WL_NO_MODULE) {
    Serial.println("Communication with WiFi module failed!");
    // don't continue
    while (true);
  }

  String fv = WiFi.firmwareVersion();
  if (fv < "1.0.0") {
    Serial.println("Please upgrade the firmware");
  }
}

void connect_WiFi() {
  // attempt to connect to Wifi network:
  while (status != WL_CONNECTED) {
    Serial.print("Attempting to connect to SSID: ");
    Serial.println(ssid);
    status = WiFi.begin(ssid, pass);
    // wait 10 seconds for connection:
    delay(10000);
  }
}

void printWEB() {

  if (client) {                             // if you get a client,
    Serial.println("---------- Received from browser client: -----------------");
    statHttpRequests++;
    String currentLine = "";                
    String httpGetLine = "";
    while (client.connected()) {            
      if (client.available()) {             
        char c = client.read();             
        Serial.write(c);                    // echo http request on terminal
        if (c != '\n' && c != '\r')
          currentLine += c;

        if (c == '\n') {
          if (currentLine.startsWith("GET "))
            httpGetLine = currentLine;
            
          if (currentLine.length() == 0) {
            // got a blank line meaning http request header is done, and we can send a http response
            
            if (httpGetLine.startsWith("GET / ")) {

              // HTTP headers always start with a response code (e.g. HTTP/1.1 200 OK)
              // and a content-type so the client knows what's coming, then a blank line:
              client.println("HTTP/1.1 200 OK");
              client.println("Content-type:text/html");
              client.println();
  
              printHumTemp();
              printStatus();

              //client.println("</body></html>");
  
            }
            else {
              // GET on anything else than '/' is not supported. This was a bug with the original web server code, where the browser
              // would also request some icon file, causing the web server to resend the page
              client.println("HTTP/1.1 404 Not Found");
              client.println();
            }
            
            // The http request header was processed and a response was sent. Now exit the request-reading loop
            break;
            
          }
          
          currentLine = "";
        } // done processing http request header line
      } // done processing http character
    }
    // close tcp connection:
    client.stop();
    Serial.println("Info: browser client link closed");
  }
}

void setup() {
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT);
  while (!Serial);
  
  enable_WiFi();
  connect_WiFi();

  server.begin();
  printWifiStatus();

  dht.begin();
}

void loop() {
  // 1372 count/second
  statLoopCnt++;
  watchdogCnt++;
  if (statLoopCnt == 0) {
    statLoopCntHigh++;
  }
  
  // Reset if no web requests has been received for 2 hours. Observed that Arduino web server would stop working,
  // for unknown reason. ping showed that WiFi connection was working.
  if (watchdogCnt > 1372*60*60*2) {
    resetFunc();
  }
  
  client = server.available();
  if (client) {
    watchdogCnt = 0;
    printWEB();
  }
  
  status = WiFi.status();
  if (status != WL_CONNECTED) {
    Serial.print("Wifi connection lost, WiFi.status = ");
    Serial.println(WiFi.status());
    statWifiReconnects++;
    connect_WiFi();
    printWifiStatus();
  }
}
2

don't use String

3

Thanks for the tip. I rewrote my program avoiding the String type, see below. My problem however still persists: after 24+ hours the webserver becomes unresponsive. Ethernet traffic however looks different: now not even a tcp connection is established. Arduino responds with a [RST, ACK]. ICMP (ping) and ARP protocol seems to be working.

My only idea is start reporting heap, stack & free ram sizes, and see if there are memory leaks in the WiFiNINA or the DHT libraries.

Any idea how to get a backdoor into an Arduino ?

#include "DHT.h"
#include <WiFiNINA.h>

#define DHTPIN 2     // Digital pin connected to the DHT sensor
#define DHTTYPE DHT22   // DHT 22  (AM2302), AM2321
DHT dht(2, DHT22);

char ssid[] = "network";             //  your network SSID (name) between the " "
char pass[] = "password";      // your network password between the " "
int status = WL_IDLE_STATUS;      //connection status
WiFiServer server(80);            //server socket
WiFiClient client = server.available();

int ledPin = 2;
int statHttpRequests = 0;
int statSensorOk = 0;
int statSensorZero = 0;
int statSensorError = 0;
int statWifiReconnects = 0;
long unsigned statLoopCnt = 0;
long unsigned statLoopCntHigh = 0;
long unsigned watchdogCnt = 0;

// 
void resetFunc() { asm volatile ("jmp 0"); }

// Max length of strings. Must be at least long enough to hold "GET / HTTP".
#define MAX_LEN 120

void add_char(char dest_str[], char new_char) {
  int slen = strlen(dest_str);
  if (slen < MAX_LEN-1) {
    dest_str[slen] = new_char;
    dest_str[slen+1] = '\0';
  }
}

void printStatus() {
  client.print("<br>http_request ");
  client.print(statHttpRequests);
  client.print("<br>sensor_ok ");
  client.println(statSensorOk);
  client.print("<br>sensor_zero ");
  client.println(statSensorZero);
  client.print("<br>sensor_err ");
  client.println(statSensorError);
  client.print("<br>wifi_rssi ");
  client.print(WiFi.RSSI());
  client.print("dBm<br>");
  client.print("wifi_reconnects ");
  client.print(statWifiReconnects);
  client.print("<br>statLoopCnt ");
  client.print(statLoopCnt);
}

void printHumTemp() {
  // Reading temperature or humidity takes about 250 milliseconds!
  // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
  float h = dht.readHumidity();
  // Read temperature as Celsius (the default)
  float t = dht.readTemperature();
  
  // Check if any reads failed and exit early (to try again).
  if (isnan(h) || isnan(t)) {
    statSensorError++;
    client.println("sensor1 ?? ??");
    // The 'F' macro moves the constant string from the 6KB ram to the 48KB flash 
    Serial.println(F("Warning: failed to read from DHT sensor"));
    return;
  } else if (h == 0.0 || t == 0.0) {
    statSensorZero++;
  } else {
    statSensorOk++;
  }

  // Rendering of html removes multiple spaces.
  client.print("sensor1 ");
  client.print(h, 1);
  client.print("%RH ");
  client.print(t, 1);
  client.println("degC<br>");
  
}

void printWifiStatus() {
  // print the SSID of the network you're attached to:
  Serial.print("SSID: ");
  Serial.println(WiFi.SSID());

  // print your board's IP address:
  IPAddress ip = WiFi.localIP();
  Serial.print("IP Address: ");
  Serial.println(ip);

  // print the received signal strength:
  long rssi = WiFi.RSSI();
  Serial.print("signal strength (RSSI):");
  Serial.print(rssi);
  Serial.println(" dBm");

  Serial.print("To see this page in action, open a browser to http://");
  Serial.println(ip);
}

void webWifiStatus () {
  // same as 'printWifiStatus' but as a web line
  client.print("SSID ");
  client.println(WiFi.SSID());

  long rssi = WiFi.RSSI();
  client.print("RSSI ");
  client.print(rssi);
  client.println(" dBm");
}

void enable_WiFi() {
  // check for the WiFi module:
  if (WiFi.status() == WL_NO_MODULE) {
    Serial.println("Communication with WiFi module failed!");
    // don't continue
    while (true);
  }

  String fv = WiFi.firmwareVersion();
  if (fv < "1.0.0") {
    Serial.println("Please upgrade the firmware");
  }
}

void connect_WiFi() {
  // attempt to connect to Wifi network:
  while (status != WL_CONNECTED) {
    Serial.print("Attempting to connect to SSID: ");
    Serial.println(ssid);
    // Connect to WPA/WPA2 network. Change this line if using open or WEP network:
    status = WiFi.begin(ssid, pass);

    // wait 10 seconds for connection:
    delay(10000);
  }
}

// Longest http line seen:
//   Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
// but only needs to be long enough to handle "GET / http1.1"
char currentLine[MAX_LEN];
char httpGetLine[MAX_LEN];
int curlen;
void printWEB() {

  if (client) {                             // if you get a client,
    Serial.println("---------- Received from browser client: -----------------");
    statHttpRequests++;
    currentLine[0] = '\0';                
    httpGetLine[0] = '\0';
    while (client.connected()) {            
      if (client.available()) {             
        char c = client.read();             
        Serial.write(c);                    // echo http request on terminal
        if (c != '\n' && c != '\r')
          add_char(currentLine, c);
          
        if (c == '\n') {
          if (strncmp(currentLine, "GET ", 4) == 0)
            // httpGetLine = currentLine;
            strlcpy(httpGetLine, currentLine, sizeof(httpGetLine));
            
          if (strlen(currentLine) == 0) {
            // got a blank line meaning http request header is done, and we can send a http response
            
            if (strncmp(httpGetLine, "GET / HTTP", 10) == 0) {

              // HTTP headers always start with a response code (e.g. HTTP/1.1 200 OK)
              // and a content-type so the client knows what's coming, then a blank line:
              client.println("HTTP/1.1 200 OK");
              client.println("Content-type:text/html");
              client.println();
  
              // To view the raw html in Chrome: right-click and select 'View page source'. The 'html' and 'head' tags
              // are not required. Without these Chrome still renders page ok.
              //
              //client.println("<html><head></head>");
              //client.println("<body>");
              
              printHumTemp();
              printStatus();

              //client.println("</body></html>");
  
            }
            else {
              // GET on anything else than '/' is not supported. This was a bug with the original web server code, where the browser
              // would also request some icon file, causing the web server to resend the page
              client.println("HTTP/1.1 404 Not Found");
              client.println();
            }
            
            // The http request header was processed and a response was sent. Now exit the request-reading loop
            break;
            
          }
          
          currentLine[0] = '\0';
        } // done processing http request header line
      } // done processing http character
    }
    // close tcp connection:
    client.stop();
    Serial.println("Info: browser client link closed");
  }
}

void setup() {
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT);
  while (!Serial);
  
  enable_WiFi();
  connect_WiFi();

  server.begin();
  printWifiStatus();

  dht.begin();
}

void loop() {
  // 1372 count/second
  statLoopCnt++;
  watchdogCnt++;
  if (statLoopCnt == 0) {
    statLoopCntHigh++;
  }
  
  // Reset if no web requests has been received for 2 hours. Observed that Arduino web server would stop working,
  // for unknown reason. ping showed that WiFi connection was working.
  if (watchdogCnt > 1372*60*60*2) {
    resetFunc();
  }
  
  client = server.available();
  if (client) {
    watchdogCnt = 0;
    printWEB();
  }
  
  status = WiFi.status();
  if (status != WL_CONNECTED) {
    Serial.print("Wifi connection lost, WiFi.status = ");
    Serial.println(WiFi.status());
    statWifiReconnects++;
    connect_WiFi();
    printWifiStatus();
  }
}
4

I don't think it is a problem with WiFiNINA. I test it in my large project with 3 servers and it works pretty good.
I use fw an library build form latest source code. But there are no bugs fixed compared to released versions.

5

My WiFiNINA WiFiServer is exposed to the internet, and can therefore potentially see malformed / malicious packets. Is this also true in your usage of WiFiNINA ?

The last 3 WiFiServer crashes/unresponsiveness happens after 2-6 days of ok functioning. When analyzing traffic to the unresponsive Arduino, I can see ok TCP handshake establishing a connection. Then internet web browser sends "GET /" request to Arduino, and WiFiNINA responds by closing the TCP connection with a TCP FIN packet. This indicates that WiFiServer is not working, but TCP stack works fine.