title: The use of "if (strcmp(URL, "/") == 0)" in Arduino network sketches
body: <p>I'm trying to understand the "if (strcmp(URL, "/") == 0)" line in the Arduino sketch below (see the sendMyPage function about halfway down): </p>
  
  <pre><code>#include &lt;WiServer.h&gt;
  
  #define WIRELESS_MODE_INFRA 1
  #define WIRELESS_MODE_ADHOC 2
  #define AREF_VOLTAGE 5
  const int tmpPin = A0;
  int tmpReading = 0;
  // Wireless configuration parameters ----------------------------------------
  unsigned char local_ip[] = {192,168,31,199}; // IP address of WiShield
  unsigned char gateway_ip[] = {192,168,1,1}; // router or gateway IP address
  unsigned char subnet_mask[] = {255,255,255,0}; // subnet mask for the local network
  const prog_char ssid[] PROGMEM = {"MERCURY_7F3F70"}; // max 32 bytes
  
  unsigned char security_type = 3; // 0 - open; 1 - WEP; 2 - WPA; 3 - WPA2
  
  // WPA/WPA2 passphrase
  const prog_char security_passphrase[] PROGMEM = {"11163127"}; // max 64 characters
  
  // WEP 128-bit keys
  // sample HEX keys
  prog_uchar wep_keys[] PROGMEM = { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, // Key 0
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // Key 1
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // Key 2
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 // Key 3
  };
  
  // setup the wireless mode
  // infrastructure - connect to AP
  // adhoc - connect to another WiFi device
  unsigned char wireless_mode = WIRELESS_MODE_INFRA;
  
  unsigned char ssid_len;
  unsigned char security_passphrase_len;
  // End of wireless configuration parameters ----------------------------------------
  float testTmp (void){
    tmpReading = analogRead (tmpPin);
    float voltage = tmpReading * AREF_VOLTAGE;
    voltage /= 1023;
    float tmpC = (voltage - 0.5) * 100;
    return tmpC;
  }
  
  // This is our page serving function that generates web pages
  **boolean sendMyPage(char* URL)** {
  
      // Check if the requested URL matches "/"
      **if (strcmp(URL, "/") == 0) {**
          // Use WiServer's print and println functions to write out the page content
          float tmpC = testTmp ();
          WiServer.print("&lt;html&gt;");
  //        WiServer.print("Hello World!");
          WiServer.print(tmpC);
          WiServer.print("&lt;/html&gt;");
  
          // URL was recognized
          return true;
      }
      // URL not found
      return false;
  }
  
  
  void setup() {
    // Initialize WiServer and have it use the sendMyPage function to serve pages
    WiServer.init(sendMyPage);
  
    // Enable Serial output and ask WiServer to generate log messages (optional)
    Serial.begin(57600);
    WiServer.enableVerboseMode(true);
  }
  
  void loop(){
  
    // Run WiServer
    WiServer.server_task();
  
    delay(10);
  }
  </code></pre>
  
  <p>It seems that the function accepts a URL as an argument, and sends data to the page using WiSever.print if the URL is valid. But how does  'if (strcmp(URL, "/") == 0)' determine if the URL is good?</p>
  
  <p>I've seen this kind of check before, but don't understand how it works.</p>
  
  <p>Thanks!</p>