/*
* Cettia
* http://cettia.io/projects/cettia-protocol/
*
* Copyright 2015 the original author or authors.
* Licensed under the Apache License, Version 2.0
* http://www.apache.org/licenses/LICENSE-2.0
*/
var events = require("events");
var url = require("url");
var http = require("http");
var createBaseTransport = require("./transport-base-transport");
http.globalAgent.maxSockets = Infinity;It creates a base transport which provides common functionalities of HTTP transport.
module.exports = function(uri, options) {A transport object.
var self = createBaseTransport(uri, options);A flag to mark the transport is sending data now.
var sending = false;A waiting queue for messages to be sent to the server.
var queue = [];For the client to send message to the server. In order to guarantee message is sent in
order, the above sending and queue are used.
self.write = function(data) {If sending is false, sets sending to true and sends data immediately without
going through the queue.
if (!sending) {
sending = true;
send(data);If not, adds data to the waiting queue. Then it will be sent through the queue later.
} else {
queue.push(data);
}
function send(data) {
var reqOpts = url.parse(uri);Somehow it’s turned out that KeepAlive Agent is required on Node 4+.
reqOpts.agent = new http.Agent({keepAlive: true});Prepares for the request headers.
reqOpts.headers = {};id param should be added to query. As it has already transport param, & can be
preceded safely.
reqOpts.path += "&id=" + encodeURIComponent(self.id);The request’s method should be POST.
reqOpts.method = "POST";Any error occurred when performing a request should propagate to transport.
function onerror(error) {
self.emit("error", error);
}If the underlying connection of request-response was closed, closes the connection this transport established if it is opened.
function onclose() {
if (self.opened) {It will fire close event finally.
self.close();
}
}The server is supposed to send the response after reading the request body.
function onresponse() {If there are pending data in the queue, removes the first one from the queue and sends it one-by-one.
if (queue.length) {FYI, [1,2,3].shift() returns in 1 and results in [2,3].
send(queue.shift());If not, set false to sending as all data in the waiting queue are sent.
} else {
sending = false;
}
}data should be either a Buffer or a string.
if (typeof data === "string") {The content type header should be text/plain; charset=utf-8 for text message.
reqOpts.headers["content-type"] = "text/plain; charset=utf-8";The final body should be prefixed with data= and encoded in utf-8.
http.request(reqOpts).on("error", onerror).on("close", onclose).on("response", onresponse)
.end("data=" + data, "utf-8");
} else {The content type header should be application/octet-stream for binary message.
reqOpts.headers["content-type"] = "application/octet-stream";
http.request(reqOpts).on("error", onerror).on("close", onclose).on("response", onresponse)
.end(data);
}
}
};
self.close = function() {Aborts the real connection. abort should be implemented by others and ensure that
close event is fired.
self.abort();Server may not detect disconnection for some reason. Notifies the server of disconnection
of this connection to make sure. In this request, id param should be added to query and
when param should be set to abort.
var reqOpts = url.parse(uri + "&when=abort&id=" + encodeURIComponent(self.id));Somehow it’s turned out that KeepAlive Agent is required on Node 4+.
reqOpts.agent = new http.Agent({keepAlive: true});
http.request(reqOpts)Node.js kills the process by default when an error event is fired if there is no
listener for it. However, a user doesn’t need to be notified of an error from this
request as it is just for the server.
.on("error", function() {
}).end();
return this;
};
return self;
};