/*
* Cettia
* http://cettia.io/projects/cettia-protocol/
*
* Copyright 2015 The Cettia Project
* Licensed under the Apache License, Version 2.0
* http://www.apache.org/licenses/LICENSE-2.0
*/
var events = require("events");
var WebSocket = require("ws");This function is exposed to the module’s transport module’s
createWebSocketServer as a factory to create server which consumes
WebSocket connection and produces transport.
module.exports = function() {A transport server object.
var self = new events.EventEmitter();A factory to upgrade HTTP exchange to WebSocket.
var webSocketUpgrader = new WebSocket.Server({noServer: true});A link between Cettia WebSocket transport protocol and Node.js. req,
sock and head are expected to be passed from Node.js’s http/https
module’ server’ upgrade event.
self.handle = function(req, sock, head) {
webSocketUpgrader.handleUpgrade(req, sock, head, function(ws) {
self.emit("transport", createWebSocketTransport(ws));
});
};
return self;
};WebSocket is a protocol designed for a full-duplex communications over a TCP connection.
function createWebSocketTransport(ws) {A transport object.
var self = new events.EventEmitter();Simply delegates WebSocket’s events to transport and transport’s behaviors to WebSocket.
ws.onmessage = function(event) {event.data is a message. It is string if text frame is sent and
Buffer if binary frame is sent.
if (typeof event.data === "string") {
self.emit("text", event.data);
} else {
self.emit("binary", event.data);
}
};
ws.onerror = function(error) {
self.emit("error", error);
};A flag to check the transport is opened.
var opened = true;
ws.onclose = function() {
opened = false;
self.emit("close");
};
self.send = function(data) {Allows to send data only it is opened. If not, fires an error.
if (opened) {If data is string, a text frame is sent, and if it’s Buffer, a
binary frame is sent.
ws.send(data);
} else {
self.emit("error", new Error("notopened"));
}
return this;
};
self.close = function() {
ws.close();
return this;
};
return self;
}