Arduino/libraries/Ethernet/examples/TwitterClient/TwitterClient.ino

/*
  Twitter Client with Strings
 
 This sketch connects to Twitter using an Ethernet shield. It parses the XML
 returned, and looks for <text>this is a tweet</text>
 
 You can use the Arduino Ethernet shield, or the Adafruit Ethernet shield, 
 either one will work, as long as it's got a Wiznet Ethernet module on board.
 
 This example uses the DHCP routines in the Ethernet library which is part of the 
 Arduino core from version 1.0 beta 1
 
 This example uses the String library, which is part of the Arduino core from
 version 0019.  
 
 Circuit:
  * Ethernet shield attached to pins 10, 11, 12, 13
 
 created 21 May 2011
 updates 2 Mar 2012
 by Tom Igoe
 
 This code is in the public domain.
 
 */
#include <SPI.h>
#include <Ethernet.h>


// Enter a MAC address and IP address for your controller below.
// The IP address will be dependent on your local network:
byte mac[] = { 
  0xDE,0xAD,0xBE,0xEF,0xFE,0xED };
IPAddress ip(192,168,1,20);

// initialize the library instance:
EthernetClient client;

const unsigned long requestInterval = 60000;  // delay between requests

char serverName[] = "api.twitter.com";  // twitter URL

boolean requested;                   // whether you've made a request since connecting
unsigned long lastAttemptTime = 0;            // last time you connected to the server, in milliseconds

String currentLine = "";            // string to hold the text from server
String tweet = "";                  // string to hold the tweet
boolean readingTweet = false;       // if you're currently reading the tweet

void setup() {
  // reserve space for the strings:
  currentLine.reserve(256);
  tweet.reserve(150);

// initialize serial:
  Serial.begin(9600);
  // attempt a DHCP connection:
  Serial.println("Attempting to get an IP address using DHCP:");
  if (!Ethernet.begin(mac)) {
    Serial.println("failed to get an IP address using DHCP, trying manually");
    // if DHCP fails, start with a hard-coded address:
    Ethernet.begin(mac, ip);
  }
  Serial.print("My IP address:");
  Serial.println(ip);
  // connect to Twitter:
  connectToServer();
}



void loop()
{
  if (client.connected()) {
    if (client.available()) {
      // read incoming bytes:
      char inChar = client.read();

      // add incoming byte to end of line:
      currentLine += inChar; 

      // if you get a newline, clear the line:
      if (inChar == '\n') {
        currentLine = "";
      } 
      // if the current line ends with <text>, it will
      // be followed by the tweet:
      if ( currentLine.endsWith("<text>")) {
        // tweet is beginning. Clear the tweet string:
        readingTweet = true; 
        tweet = "";
      }
      // if you're currently reading the bytes of a tweet,
      // add them to the tweet String:
      if (readingTweet) {
        if (inChar != '<') {
          tweet += inChar;
        } 
        else {
          // if you got a "<" character,
          // you've reached the end of the tweet:
          readingTweet = false;
          Serial.println(tweet);   
          // close the connection to the server:
          client.stop(); 
        }
      }
    }   
  }
  else if (millis() - lastAttemptTime > requestInterval) {
    // if you're not connected, and two minutes have passed since
    // your last connection, then attempt to connect again:
    connectToServer();
  }
}

void connectToServer() {
  // attempt to connect, and wait a millisecond:
  Serial.println("connecting to server...");
  if (client.connect(serverName, 80)) {
    Serial.println("making HTTP request...");
  // make HTTP GET request to twitter:
    client.println("GET /1/statuses/user_timeline.xml?screen_name=arduino&count=1 HTTP/1.1");
    client.println("HOST: api.twitter.com");
    client.println();
  }
  // note the time of this connect attempt:
  lastAttemptTime = millis();
}