Socket.io is a JavaScript library that enables real-time bidirectional event-based communication between web clients and servers. It uses multiple transport mechanisms including WebSocket, polling, and flash sockets and has built-in support for reconnecting clients and detecting disconnections through heartbeats. Socket.io allows for multiple sockets under a single connection using namespaces and has a lightweight protocol that sits on top of HTTP.

1. socket.io
in 10 minutes

2. what it is?
• WebSocket-like API
• Multiple transport support (old user
agents, mobile browsers, etc).
• Multiple sockets under the same
connection (namespaces).
• Disconnection detection through
heartbeats.

3. what it is?
• Reconnection support with buffering
(ideal for mobile devices or bad
networks)
• Lightweight protocol that sits on top of
HTTP.

4. socket.io states
• disconnected
• disconnecting
• connected
• connecting

5. transport connection
• closed
• closing
• open
• opening

6. supported transports
• xhr-polling
• xhr-multipart
• htmlfile
• websocket
• flashsocket
• jsonp-polling

7. code
var socket = io.listen(app);
var clients = {};
socket.on('connection', function(client) {
var id = client.sessionId;
clients[id] = client;
client.on('disconnect', function(){
delete clients[id]
})
});

8. code
$.each(config.logfile, function(index, log) {
tail = spawn('tail', ['-n', '1', '-f', log])
tail.stdout.on('data', function (data) {
$.each(clients, function(index, client) {
client.send(json({output: data.toString(), file: log}));
});
})
tail.stderr.on('data', function (data) {
$.each(clients, function(index, client) {
client.send(json({output: data.toString(), file: log}));
});
})
});

9. code
<script>
var socket = new io.Socket(#{"'" + hostname + "'"});
socket.connect();
socket.on('message', function(data) {
log = JSON.parse(data)
if (log.file == $('#logfiles').val()){
$('.logs').append(log.output);
}
});
</script>

10. our maptail fork

11. server logs

12. credits
• https://github.com/LearnBoost/
socket.io-spec
• https://github.com/LearnBoost/
Socket.IO-node-client
• https://github.com/stagas/maptail