How to have multiple connections to a Arduino webserver? - http

Question

I have an Arduino running a webserver that is receiving data every 2 seconds. I CAN connect to its IP address by typing into the browser. I also created a web app that pulls data from this IP address every time new data comes in. The issue is that I need to access the IP address with the web app while another program is accessing it. Currently only one program can access at a time. I would like to have a Python script pulling data from the IP address constantly and still allow the web app to connect to view it live. How can I achieve this?
Arduino code with a lot of other stuff removed...
WiFiServer server(80); //server socket
WiFiClient client_1 = server.available();
void setup() {
Serial.begin(9600);
enable_WiFi(); // function to enable wifi
connect_WiFi(); // function to connect to wifi
server.begin();
}
void loop() {
client_1 = server.available();
if (client_1) {
printWEB(client_1); // this posts the data as text to the web IP address
}
delay(2000);
}
void printWEB(WiFiClient client) {
if (client) { // if you get a client,
Serial.println("new client"); // print a message out the serial port
String currentLine = ""; // make a String to hold incoming data from the client
while (client.connected()) { // loop while the client's connected
if (client.available()) { // if there's bytes to read from the client,
char c = client.read(); // read a byte, then
Serial.write(c); // print it out the serial monitor
if (c == '\n') { // if the byte is a newline character
// if the current line is blank, you got two newline characters in a row.
// that's the end of the client HTTP request, so send a response:
if (currentLine.length() == 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("Access-Control-Allow-Origin: *");
client.println("Access-Control-Allow-Methods: GET");
client.println("Content-type: application/json");
client.println();
moistureReading = analogRead(A1);
tmpString = dataPosted;
tmpString.replace("%moistureData%", String(moistureReading) );
client.flush();
client.print( tmpString );
// The HTTP response ends with another blank line:
client.println();
// break out of the while loop:
break;
}
else { // if you got a newline, then clear currentLine:
currentLine = "";
}
}
else if (c != '\r') { // if you got anything else but a carriage return character,
currentLine += c; // add it to the end of the currentLine
}
}
}
// close the connection:
client.stop();
Serial.println("client disconnected");
}
}

Answer 1

The solution here was to take the delay off of the arduino code by simply removing the sleep function (Turns out this is not required). I then had to create a delay in all of my fetching codes. The React.js needed a sleep function and the python script needed a sleep function. This allows the two platforms to collect data from the same IP Address simultaneously. I needed a minimum of about 5-10 second sleep for both apps in order for this to work. I initially tried 1 second for each and it didn't work.

Answer 2

The webserver as programmed on your Arduino can only serve one request from a client at a time, not two simultaneously.
If two clients are doing requests in a loop, and are doing that fairly quickly, there will be situations where one client is blocking access for the other.
Try making the two clients much slower, i.e. retrieve information at a much lower frequency, just to see if the Arduino can keep up then.
Also, make the webserver on the Arduino as fast as possible, and call it as often as possible.
So, don't put delay()s in the loop, or anywhere else, and try to do the analogread() and the return string preparation outside of the webserver code and in the loop() every x seconds using millis(), so as little time as possible is spent in the webserver code.