ESP8266 unwanted delay using client.readStringUntil(), with Microsoft SQL server - sql-server

Question

My goal is to read the number of button press within a period(30s), upload it to a Microsoft SQl table using a php script. On the table, there is another column which adds in accumulated sum of the presses, which will be echo-ed back by the php script, and be read by the ESP8266 board.
So everything went through: I can read the count, upload it, read the accumulated sum back. The issue is it always takes ~5s in order to get a value back from the server. Attached is my troubleshooting:Serial Windows
It takes almost instantly to connect to the server(~100ms) but 5s to read the data that be echo-ed.
My guess was the php script takes time to run to the line where it echo out the value, but same delay(~5s) happens even if I tried a simple script(just echo).
Is this how the server behaves (not giving out the data right away) or is this how Arduino code (client.readStringUntil()) behaves?
Here is my code:
#include <SPI.h>
#include <ESP8266WiFi.h>
// Wifi Connection config
const char* ssid = "------";
const char* password = "------";
WiFiServer server(80);
IPAddress dbserver(10,1,1,138);
void setup_wifi()
{
delay(10);
// We start by connecting to a WiFi network
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
Serial.println("");
Serial.println("WiFi connected");
}
void setup()
{
Serial.begin(115200);
// Connect to WiFi network
setup_wifi();
}
void loop ()
{
WiFiClient client;
const int httpPort = 80;
bool conn = client.connect(dbserver,httpPort);
if (!conn) {
Serial.println("connection failed");
return;
}
else {
// call php script on the server(echo 1 value)
client.print("GET /test10.php HTTP/1.1");
client.println("Host: 10.1.1.138");
client.println("Connection: close");
client.println(); // Empty line
// Read from the server
Serial.println(millis()); // millis start reading
unsigned long timeout = millis();
while (client.available()==0){
if (millis()-timeout >1000){
Serial.println(">>> Client Timeout !");
client.stop();
}
}
Serial.println(millis()); // millis get the data stream
while (client.available()){
String line = client.readStringUntil('\r');
Serial.println(String(millis()) + " >>> "+line); // millis get each
// data line
}
delay(10);
client.stop(); // Closing connection to server
Serial.println("done");
}
delay(30000);
}
And is there any other way to fetch the data from the server to an ESP8266 module?
Thank you,
-Danny-

Answer 1

[SOLVED]: I need to set the Timeout parameter for the readStringUntil() function.
readStringUntil() is a blocking function. I will wait until it sees a char ('\r' in your case) or the timeout exceeds.
Just need to add client.setTimeout as:
WifiClient client;
client.setTimeout(10);
Still not sure if this practice is recommended, and how smaller should I go to for timeout?

Answer 2

Another solution would be using freeRTOS, and put the webserver in a separate task.
Then it can wait forever until a request is coming in.