From b1c444883f4c7b5ad66c347365f39a15c909dccf Mon Sep 17 00:00:00 2001
From: Paul Querna <pquerna@apache.org>
Date: Mon, 13 Dec 2010 23:27:40 -0800
Subject: [PATCH] Add basic chat client & server

---
 udp/chat-client.js | 24 ++++++++++++++++
 udp/chat-server.js | 72 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 96 insertions(+)
 create mode 100644 udp/chat-client.js
 create mode 100644 udp/chat-server.js

diff --git a/udp/chat-client.js b/udp/chat-client.js
new file mode 100644
index 0000000..8e0bb7f
--- /dev/null
+++ b/udp/chat-client.js
@@ -0,0 +1,24 @@
+/* This code is PUBLIC DOMAIN, and is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND. See the accompanying 
+ * LICENSE file.
+ */
+
+var Buffer = require('buffer').Buffer;
+var dgram = require('dgram');
+
+var stdin = process.openStdin();
+stdin.setEncoding('utf8');
+
+SERVER_HOST = '127.0.0.1';
+SERVER_PORT = 7000;
+
+var sock = dgram.createSocket("udp4");
+
+stdin.on('data', function (input) {
+  var buf = new Buffer(input);
+  sock.send(buf, 0, buf.length, SERVER_PORT, SERVER_HOST);
+});
+
+sock.on('message', function (buf) {
+  process.stdout.write(buf.toString());
+});
diff --git a/udp/chat-server.js b/udp/chat-server.js
new file mode 100644
index 0000000..b98eb1e
--- /dev/null
+++ b/udp/chat-server.js
@@ -0,0 +1,72 @@
+/* This code is PUBLIC DOMAIN, and is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND. See the accompanying 
+ * LICENSE file.
+ */
+
+var Buffer = require('buffer').Buffer;
+var dgram = require('dgram');
+var log = require('sys').log;
+var CLIENT_GENERATION_GAP = 10;
+var CLIENT_CLEANER_INTERVAL = 1000;
+SERVER_HOST = '127.0.0.1';
+SERVER_PORT = 7000;
+
+function ts() {
+  return Math.round(new Date().getTime() / 1000);
+}
+
+var clients = {};
+var generation = ts();
+var sock = null;
+
+var si = setInterval(function() {
+  generation = ts();
+  for (var ckey in clients) {
+    if (clients.hasOwnProperty(ckey)) {
+      var gap = generation - clients[ckey];
+      /* No ping from this client in X seconds, assume its dead. */
+      if (gap > CLIENT_GENERATION_GAP) {
+        delete clients[ckey];
+      }
+    }
+  }
+}, CLIENT_CLEANER_INTERVAL);
+
+function updateTimeout(key) {
+  clients[key] = generation;
+}
+
+function broadcast(buf) {
+  var c = 0;
+  for (var ckey in clients) {
+    if (clients.hasOwnProperty(ckey)) {
+      var host = ckey.slice(0, ckey.lastIndexOf(':'));
+      var port = parseInt(ckey.slice(ckey.lastIndexOf(':')+1), 10);
+      c++;
+      sock.send(buf, 0, buf.length, port, host);
+    }
+  }
+  log('Broadcasted to '+ c + ' clients');
+}
+
+function processMsg(msg, peer) {
+  var str = msg.toString();
+  str = str.replace(/[\n\r]/g, ""); 
+  if (str.length > 0) {
+    var buf = new Buffer(peer.address + ":"+ peer.port + "> "+  str + '\n');
+    broadcast(buf);
+  }
+}
+
+sock = dgram.createSocket("udp4", function (msg, peer) {
+  var key = peer.address + ":" + peer.port;
+  log('got message');
+  updateTimeout(key);
+  processMsg(msg, peer);
+});
+
+sock.on('listening', function() {
+  log('Bound to '+ SERVER_HOST + ':' + SERVER_PORT);
+});
+sock.bind(SERVER_PORT, SERVER_HOST);
+