Wifi server to control led on and off from local webpage.. - ..if statement doesnt work...

Question

Im a newbie on this arduino thing and I would like to build a curtain remotecontrolled from a local webpage with 2 buttons... a up an a down...

I got the connection via my phone the the local page with the buttons. :D

My problem on this one is that the buttons' if statement (command == on); doesnt work or in other words the client.println(command); get the "on" command and write it on the page... but it dont do the function in the if statement (the button)...

Can anybody help me...? it should be simple..:D

 #include <Bridge.h>
 #include <YunServer.h>
 #include <YunClient.h>
 int LEDPIN = 3; // your LED PIN
 YunServer server;
 String readString;
 void setup() {
 // Start our connection
 Serial.begin(9600);
 pinMode(LEDPIN,OUTPUT);
 digitalWrite(LEDPIN,HIGH); // turn on Led while connecting
 Bridge.begin(); 
 // Show a fancy flash pattern once connected
 digitalWrite(LEDPIN,LOW); 
 delay(150);
 digitalWrite(LEDPIN,HIGH); 
 delay(150);
 digitalWrite(LEDPIN,LOW); 
 delay(150);
 digitalWrite(LEDPIN,HIGH); 
 delay(150);
 digitalWrite(LEDPIN,LOW); 
 delay(150);
 // Disable for some connections:
 // Start listening for connections 
 // server.listenOnLocalhost();
 server.begin();
}
/* ------------------------------------------------*/
/* --------------- End WIFI connection ------------*/
/* ------------------------------------------------*/
void loop() {
 YunClient client = server.accept();
 if (client) {
 process(client);
 client.stop();
 }
 delay(50);
}
void process(YunClient client) {
 String command = client.readStringUntil('\\'); 
 client.println("Status: 200");
 client.println("Content-type: text/html");
 client.println();
 client.println("<B><Center><br><br><br>");
 client.println("<a href='/arduino/on\\'>ON</a><br><br><br>");
 client.println("<a href='/arduino/off\\'>OFF</a><br><br><br>");
 client.print("Command: ");
 client.println(command);
 client.println("</B></Center>");
/* ------------------------------------------------*/
/* ------------------- Buttons --------------------*/
/* ------------------------------------------------*/
 if (command == "on") {
 digitalWrite(LEDPIN,HIGH);
 digitalWrite(13,HIGH);
 }
 if (command == "off") {
 digitalWrite(LEDPIN,LOW);
 digitalWrite(13,LOW); 
 }
}

• Chris Stratton: Perhaps your command isn't exactly "on" or "off" - could it have trailing characters? Try displaying its length in your debugging message, or only comparing only the beginning with startsWith. Also, comparing your code to a reference example, you seem to have replaced a single forward slash with an escaped backslash in the readStringUntil() so perhaps you are mistakenly reading the whole thing.
• TDHofstetter: Is it possible you have a case sensitivity issue ("ON" != "on")?

Answer 1

Pretty sure your problem is coming from the fact that you chose to use the backslash as your terminator character. The backslash requires special handling when encoded as a URL. You can observe this by Googling for "\" and and the results page you'll see your query in the address bar assigned to the "q" variable: q=%5C my entire URL looked like this, you may have something a bit different: https://www.google.com/?gws_rd=ssl#q=%5C

Ok - so if you want a quick fix, stop using the \ to terminate your commands, since backslashes are often used to help sort out special characters (like "TAB" as \t) it's a a really bad choice, but an honest mistake.

If you change your code to generate links terminated with dashes you can get around the issue

client.println("<a href='/arduino/on-'>ON</a><br><br><br>");
client.println("<a href='/arduino/off-'>OFF</a><br><br><br>");

and of course change your readStringUntil invocation too

client.readStringUntil('-');

Edit: You might want to use the "" if the hostname part of your URL contains a space: http://my-web-server.com/on

And one more alternative, seek the "%" instead since that's going to be used to encode the backslash. In that case you just need to change the readStringUntil()