Added DHCP and DNS-based Twitter client for Ethernet library

libraries/Ethernet/examples/TwitterClient/TwitterClient.ino

@@ -0,0 +1,124 @@
+/*
+  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
+ 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[] = { 
+  0x00, 0xAA, 0xBB, 0xCC, 0xDE, 0x01 };
+IPAddress ip(192,168,1,20);
+
+// initialize the library instance:
+Client client;
+
+const int requestInterval = 60000;  // delay between requests
+
+char serverName[] = "api.twitter.com";  // twitter URL
+
+boolean requested;                   // whether you've made a request since connecting
+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:
+  if (!Ethernet.begin(mac)) {
+    // if DHCP fails, start with a hard-coded address:
+    Ethernet.begin(mac, 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();
+}