/*
* Cettia
* http://cettia.io/projects/cettia-protocol/
*
* Copyright 2017 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");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 = [];The above sending and queue are required to guarantee messages the client sends to the serve
is sent in order.
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 = {};cettia-transport-id param should be added to query. As the URI has already
cettia-transport-name param, & can be preceded safely.
reqOpts.path += "&cettia-transport-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, cettia-transport-id param should be
added to query and cettia-transport-when param should be set to abort.
var reqOpts = url.parse(uri + "&cettia-transport-when=abort&cettia-transport-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;
};