WiFi testing program

Over in the Support category a member was recently having trouble connecting to WiFi to update firmware: Can’t connect to wifi. It occurred to me that the firmware update is not the ideal way to debug WiFi problems. So I wrote a small WiFi application where the code can be easily fiddled with to try various potential solutions to WiFi problems.

Here is the program:

// Programming example: connecting to a WiFi network and periodically exchanging UDP datagrams with the
// NTP server at time.nist.gov (port 123). UDP is an unreliable protocol in that no UDP datagram is guaranteed
// to reach its destination, so not every request for current time will be honored. Furthermore time.nist.gov
// does not allow requests less than 4 seconds apart. So this program requests the time approximately every
// 10 seconds and extrapolates the time after each 10-second request by using the jiffy clock function millis().

// This program is intended to allow debugging WiFi connection problems including DNS failures. See the highlited
// code below where the user may customize this program to use either the DHCP-supplied DNS server or a known
// good DNS server, and to attempt to connect to a NIST NTP server either by name or by IP address. If the
// connection by name fails to resolve the name, then the DNS server in use is failing.

// If the WiFi connection to the specified SSID with the specified password succeeds, and the NTP server name
// resolves, the program will display the date/time returned by the server. If datagrams get lost, there may be
// momentary pauses in updating the date/time while the UDP request is retried; occasional datagram loss is
// expected as such is the nature of UDP.

// See highlighted comments below to customize program for your network and DNS testing.

// Example coded 5/10/2020 by Frank Prindle.

#include "MAKERphone.h"
MAKERphone mp;

void setup()

  /* Set the following two strings to match your WiFi network. */
  char *SSID = "FrankNet5";
  char *WPAPassword = "1234ABCD";

  /* Disable the following line to use DHCP supplied DNS server.       */
  /* Enable the following line to use a well-known DNS server.         */
  /*    Set the first IP address to a valid static IP on your network. */
  /*    Set the second IP address to the IP address of your router.    */
  /*    Set the third IP address to your network mask.                 */
  /*    Leave the fourth IP address alone (Google DNS).                */
  int count=100;
  while(WiFi.status() != WL_CONNECTED && count--) delay(100);
  if(WiFi.status() != WL_CONNECTED)
    Serial.printf("WiFi cannot connect to given SSID with given password\n");
    statusline("WiFi Connect Failure", true);
    statusline("WiFi Connect Failure", false);
    Serial.printf("WiFi is connected\n");
    statusline("WiFi Is Connected", true);
    statusline("WiFi Is Connected", false);

void loop()
  unsigned int localPort = 8888; // Fairly arbitrary
  unsigned char inPacket[48];
  // NTP time request packet
  unsigned char outPacket[48] = {0b11100011, 0, 6, 0xEC, 0, 0 ,0, 0, 0, 0, 0, 0, 49, 0x4E, 49, 52, 0, 0, 0, 0, 0,
                                 0, 0, 0, 0 ,0 ,0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
  WiFiUDP udp;
  statusline("Trying To Resolve Server", true);

  /* Enable only one of the following two lines.                 */
  /* Enable first line to use DNS to find an NTP server by name. */
  /* Enable second line to use an NTP server's IP address.       */
  udp.beginPacket("time.nist.gov", 123); // NTP requests are to port 123
  //udp.beginPacket("", 123); // NTP requests are to port 123

  statusline("Trying To Resolve Server", false);
  udp.write(outPacket, sizeof(outPacket));
  int count=100;
  while(udp.parsePacket() < sizeof(inPacket) && --count)
    statusline("NTP Waiting For Response", true);
  statusline("NTP Waiting For Response", false);
    // NTP request honored - time is in packet
    unsigned long ms = millis();
    udp.read(inPacket, sizeof(inPacket));
    unsigned long secsSince1900 = (inPacket[40]<<24) | (inPacket[41]<<16) | (inPacket[42]<<8) | inPacket[43];
    long secsSinceEpoch = secsSince1900 - 2208988800UL;

    // Extrapolate displayed time over 10 seconds
    while(millis()-ms < 10000)
      // Extrapolate time now
      long sse = secsSinceEpoch+(millis()-ms)/1000;
      char *msg = ctime(&sse);
      Serial.printf("%s UTC\n",msg);

      // Display the extrapolated time - if top line is yellow, time is from NTP - if green, time is exratpolated
      if(sse == secsSinceEpoch) mp.display.setTextColor(TFT_YELLOW);
      else                      mp.display.setTextColor(TFT_GREEN);
      mp.display.print("FROM: time.nist.gov");
      mp.display.print("\n\n            UTC");
    // NTP request not honored (either outgoing packet or incoming packet lost)
    statusline("NTP No Response - Retry", true);
    statusline("NTP No Response - Retry", false);
  // Shut down UDP in preparation for next loop

// Display (on==true) or erase (on==false) transient status line near bottom of display
void statusline(char *msg, bool on)
  mp.display.setTextColor(on ? TFT_YELLOW : TFT_BLACK);


You can compile and upload this to the Ringo phone using the Arduino IDE after customizing it (see comments in code). If your WiFi is working well and you’ve used a valid WiFi network SSID and password, it will display the UTC date and time obtained from NTP server time.nist.gov. If the WiFi connection fails or time.nist.gov cannot be resolved to an IP address, a status line will so indicate, and you can modify the code to further explore the problem. You are obviously not limited to the code variations I’ve marked; feel free to change this in any way that benefits you and enhances your understanding of using WiFi from the Ringo phone.

This is a simple example using UDP over IP. There are other more complex protocols supported by the ESP32 WiFi library such as TCP and HTTP, which you may want to explore on your own.