Infinite stall on WiFiWebServer sample / MKR 1000 #318

andreasp79 · 2021-12-19T01:31:28Z

Using MKR 1000, Firmware version 19.6.1, WiFi101 library version 0.16.1

The sample web server code will stall forever as it waits for data never supplied by the library. This can be reproduced by running the server and continuously connecting to it from a web browser from another machine (tried with Safari 15.1 from OSX, don't think it matters). Simultaneously hitting the server from multiple machines may make the repro easier/faster, but it happens very consistently and within a few minutes for me even from one client, assuming it is constantly hitting the server with requests (i.e. keep clicking the refresh button on the browser).

During the stall, WiFiClient.connected() will return true, but WiFiClient.available() will keep returning false forever, creating an infinite loop in the sample code.

Sketch included at the bottom, but is practically identical to the sample code at https://www.arduino.cc/en/Tutorial/LibraryExamples/Wifi101WiFiWebServer. The issue happens with the sample code as well.

Minimal repro sketch:

/*

  WiFi Web Server

 A simple web server that shows the value of the analog input pins.

 using a WiFi shield.

 This example is written for a network using WPA encryption. For

 WEP or WPA, change the WiFi.begin() call accordingly.

 Circuit:

 * WiFi shield attached

 * Analog inputs attached to pins A0 through A5 (optional)

 created 13 July 2010

 by dlf (Metodo2 srl)

 modified 31 May 2012

 by Tom Igoe

 */

#include <SPI.h>
#include <WiFi101.h>

///////please enter your sensitive data in the Secret tab/arduino_secrets.h
char ssid[] = "<my ssid>";        // your network SSID (name)
char pass[] = "<my password>";    // your network password (use for WPA, or use as key for WEP)
int keyIndex = 0;                 // your network key Index number (needed only for WEP)

int status = WL_IDLE_STATUS;

WiFiServer server(80);

void setup() {

  //Initialize serial and wait for port to open:

  Serial.begin(9600);

  while (!Serial) {

    ; // wait for serial port to connect. Needed for native USB port only

  }

  // check for the presence of the shield:

  if (WiFi.status() == WL_NO_SHIELD) {

    Serial.println("WiFi shield not present");

    // don't continue:

    while (true);

  }

  // 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);

  }

  server.begin();

  // you're connected now, so print out the status:

  printWiFiStatus();
}

void loop() {

  // listen for incoming clients

  WiFiClient client = server.available();

  if (client) {

    Serial.println("new client");

    // an http request ends with a blank line

    bool currentLineIsBlank = true;

    while (client.connected()) 
    {

      if (client.available()) 
      {

        char c = client.read();

        Serial.write(c);

        // if you've gotten to the end of the line (received a newline

        // character) and the line is blank, the http request has ended,

        // so you can send a reply

        if (c == '\n' && currentLineIsBlank) {

          // send a standard http response header

          client.println("HTTP/1.1 200 OK");

          client.println("Content-Type: text/html");

          client.println("Connection: close");  // the connection will be closed after completion of the response

          client.println("Refresh: 5");  // refresh the page automatically every 5 sec

          client.println();

          client.println("<!DOCTYPE HTML>");

          client.println("<html>");

          // output the value of each analog input pin

          for (int analogChannel = 0; analogChannel < 6; analogChannel++) {

            int sensorReading = analogRead(analogChannel);

            client.print("analog input ");

            client.print(analogChannel);

            client.print(" is ");

            client.print(sensorReading);

            client.println("<br />");

          }

          client.println("</html>");

          break;

        }

        if (c == '\n') {

          // you're starting a new line

          currentLineIsBlank = true;

        }

        else if (c != '\r') {

          // you've gotten a character on the current line

          currentLineIsBlank = false;

        }

      }
      else

      {
        Serial.println("Connected was 1, but available was 0");
        // delay(1);
      }

    }

    // give the web browser time to receive the data

    delay(1);

    // close the connection:

    client.stop();

    Serial.println("client disconnected");

  }
}

void printWiFiStatus() {

  // print the SSID of the network you're attached to:

  Serial.print("SSID: ");

  Serial.println(WiFi.SSID());

  // print your WiFi shield'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");
}

The text was updated successfully, but these errors were encountered:

JAndrassy · 2022-01-09T13:54:21Z

For WiFi101 you must add && client.available() to if (client) because available() here has an undocumented 'feature'. It returns just connected client even if the client doesn't have data yet. A fix would be a breaking change for some WiFi101 users so it can only by applied for version 1.0.0 (next major version)

per1234 added topic: documentation Related to documentation for the project type: imperfection Perceived defect in any part of project labels Dec 19, 2021

JAndrassy mentioned this issue Jan 9, 2022

server.available() according to reference. with example #323

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Infinite stall on WiFiWebServer sample / MKR 1000 #318

Infinite stall on WiFiWebServer sample / MKR 1000 #318

andreasp79 commented Dec 19, 2021

JAndrassy commented Jan 9, 2022 •

edited

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Infinite stall on WiFiWebServer sample / MKR 1000 #318

Infinite stall on WiFiWebServer sample / MKR 1000 #318

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andreasp79 commented Dec 19, 2021

JAndrassy commented Jan 9, 2022 • edited Loading

JAndrassy commented Jan 9, 2022 •

edited

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