STOMP is a simple text-orientated messaging protocol. It defines an interoperable wire format so that any of the available STOMP clients can communicate with any STOMP message broker to provide easy and widespread messaging interoperability among languages and platforms (the STOMP web site has a list of STOMP client and server implementations.
WebSockets are "TCP for the Web".
When Google announced the availability ofWebSocket in Google Chrome,it explained the idea behind WebSockets:
The WebSocket API enables web applications to handle bidirectional communications with server-side process in a straightforward way. Developers have been using XMLHttpRequest ("XHR") for such purposes, but XHR makes developing web applications that communicate back and forth to the server unnecessarily complex. XHR is basically asynchronous HTTP, and because you need to use a tricky technique like long-hanging GET for sending data from the server to the browser, simple tasks rapidly become complex. As opposed to XMLHttpRequest, WebSockets provide a real bidirectional communication channel in your browser. Once you get a WebSocket connection, you can send data from browser to server by calling a send() method, and receive data from server to browser by an onmessage event handler.
In addition to the new WebSocket API, there is also a new protocol (the "WebSocket Protocol") that the browser uses to communicate with servers. The protocol is not raw TCP because it needs to provide the browser's "same-origin" security model. It's also not HTTP because WebSocket traffic differers from HTTP's request-response model. WebSocket communications using the new WebSocket protocol should use less bandwidth because, unlike a series of XHRs and hanging GETs, no headers are exchanged once the single connection has been established. To use this new API and protocol and take advantage of the simpler programming model and more efficient network traffic, you do need a new server implementation to communicate with.
The API is part of HTML5 and is supported (at various degree...) by most modern Web Browsers (including Google Chrome, Firefox and Safari on Mac OS X and iOS).
This library supports multiple version of STOMP protocols:
This library is not a pure STOMP client. It is aimed to run on the WebSockets protocol which is not TCP. Basically, the WebSocket protocol requires a handshake between the browser's client and the server to ensure the browser's "same-origin" security model remains in effect.
This means that this library can not connect to regular STOMP brokers since they would not understand the handshake initiated by the WebSocket which is not part of the STOMP protocol and would likely reject the connection.
There are ongoing works to add WebSocket support to STOMP broker so that they will accept STOMP connections over the WebSocket protocol.
HornetQ is the Open Source messaging system developed by Red Hat and JBoss.
To start HornetQ with support for STOMP Over WebSocket, download the latest version and run the following steps:
$ cd hornetq-x.y.z/examples/jms/stomp-websockets $ mvn clean install ... INFO: HQ221020: Started Netty Acceptor version 3.6.2.Final-c0d783c localhost:61614 for STOMP_WS protocol Apr 15, 2013 1:15:33 PM org.hornetq.core.server.impl.HornetQServerImpl$SharedStoreLiveActivation run INFO: HQ221007: Server is now live Apr 15, 2013 1:15:33 PM org.hornetq.core.server.impl.HornetQServerImpl start INFO: HQ221001: HornetQ Server version 2.3.0.CR2 (black'n'yellow2, 123) [c9e29e45-a5bd-11e2-976a-b3fef7ceb5df]
HornetQ is now started and listens to STOMP over WebSocket on the port 61614
.
It accepts WebSocket connections from the URL ws://localhost:61614/stomp
To configure and run HornetQ with STOMP Over WebSocket enabled, follow the instructions.
ActiveMQ is the Open Source messaging system developed by Apache. Starting with 5.4 snapshots, ActiveMQ supports STOMP Over WebSocket.
To configure and run ActiveMQ with STOMP Over WebSocket enabled, follow the instructions.
ActiveMQ Apollo is the next generation of ActiveMQ broker. From the start, Apollo supports STOMP Over WebSocket.
To configure and run Apollo with STOMP Over WebSocket enabled, follow the instructions.
RabbitMQ is Open Source messaging system sponsored by VMware.
To configure and run RabbitMQ with STOMP Over WebSocket enabled, follow the instructions to install the Web-Stomp plugin.
Stilts is a STOMP-native messaging framework which aims to address treating STOMP as primary contract for messaging, and integrating around it, instead of simply applying STOMP shims to existing services.
TorqueBox uses the Stilts project to provide its WebSockets and STOMP stack.
You can download stomp.js to use it in your Web applications
A minified version is also provided to be used in production.
This JavaScript file is generated from CoffeeScript files. See the Contribute section to download the source code or browse the annotated source code.
STOMP Over WebSocket provides a straightforward mapping from a STOMP frame to a JavaScript object.
Property | Type | Notes |
---|---|---|
command |
String | name of the frame ("CONNECT" , "SEND" , etc.) |
headers |
JavaScript object | |
body |
String |
The command
and headers
properties will always be defined but the headers
can be empty if the frame has no headers. The body
can be null
if the frame does not have a body.
STOMP JavaScript clients will communicate to a STOMP server using a ws://
URL.
To create a STOMP client JavaScript object, you need to call Stomp.client(url)
with the URL corresponding to the server's WebSocket endpoint:
var url = "ws://localhost:61614/stomp";
var client = Stomp.client(url);
The Stomp.client(url, protocols)
can also be used to override the default subprotocols provided by the library: ['v10.stomp', 'v11.stomp]'
(for STOMP 1.0 & 1.1 specifications). This second argument can either be a single string or an array of strings to specify multiple subprotocols.
Web browsers supports different versions of the WebSocket protocol. Some older browsers does not provide the WebSocket JavaScript or expose it under another name. By default, stomp.js
will use the Web browser native WebSocket
class to create the WebSocket.
However it is possible to use other type of WebSockets by using the Stomp.over(ws)
method.This method expects an object that conforms to the WebSocket definition.
For example, it is possible to use the implementation provided by the SockJS project which falls back to a variety of browser-specific transport protocols instead:
Use Stomp.client(url)
to use regular WebSockets or use Stomp.over(ws)
if you required another type of WebSocket.
Apart from this initialization, the STOMP API remains the same in both cases.
The library can also be used in node.js application by using the stompjs npm package.
$ npm install stompjs
In the node.js app, require the module with:
var Stomp = require('stompjs');
To connect to a STOMP broker over a TCP socket, use the Stomp.overTCP(host, port)
method:
var client = Stomp.overTCP('localhost', 61613);
To connect to a STOMP broker over a Web Socket, use instead the Stomp.overWS(url)
method:
var client = Stomp.overWS('ws://localhost:61614/stomp');
Apart from this initialization, the STOMP API remains the same whether it is running in a Web browser or in node.js application.
Once a STOMP client is created, it must call its connect()
method to effectively connect and authenticate to the STOMP server. The method takes two mandatory arguments, login
and passcode
corresponding to the user credentials.
Behind the scene, the client will open a connection using a WebSocket and send a CONNECT frame.
The connection is done asynchronously: you have no guarantee to be effectively connected when the call to connect
returns. To be notified of the connection, you need to pass a connect_callback
function to the connect()
method:
var connect_callback = function() {
// called back after the client is connected and authenticated to the STOMP server
};
But what happens if the connection fails? the connect()
method accepts an optional error_callback
argument which will be called if the client is not able to connect to the server. The callback will be called with a single argument, an error object corresponding to STOMP ERROR frame:
var error_callback = function(error) {
// display the error's message header:
alert(error.headers.message);
};
The connect()
method accepts different number of arguments to provide a simple API to use in most cases:
client.connect(login, passcode, connectCallback);
client.connect(login, passcode, connectCallback, errorCallback);
client.connect(login, passcode, connectCallback, errorCallback, host);
where login
, passcode
are strings and connectCallback
and errorCallback
are functions (some brokers also require to pass a host String).
The connect()
method also accepts two other variants if you need to pass additional headers:
client.connect(headers, connectCallback);
client.connect(headers, connectCallback, errorCallback);
where header
is a map and connectCallback
and errorCallback
are functions.
Please note that if you use these forms, you must add the login
, passcode
(and eventually host
) headers yourself:
var headers = {
login: 'mylogin',
passcode: 'mypasscode',
// additional header
'client-id': 'my-client-id'
};
client.connect(headers, connectCallback);
To disconnect a client from the server, you can call its disconnect()
method. The disconnection is asynchronous: to be notified when the disconnection is effective, the disconnect
method takes an optional callback
argument.
client.disconnect(function() {
alert("See you next time!");
};
When a client is disconnected, it can no longer send or receive messages.
If the STOMP broker accepts STOMP 1.1 frames, heart-beating is enabled by default.
The client
object has a heartbeat
field which can be used to configure heart-beating by changing its incoming
and outgoing
integer fields (default value for both is 10000
ms):
client.heartbeat.outgoing = 20000; // client will send heartbeats every 20000ms
client.heartbeat.incoming = 0; // client does not want to receive heartbeats
// from the server
The heart-beating is using window.setInterval()
to regularly send heart-beats and/or check server heart-beats.
When the client is connected to the server, it can send STOMP messages using the send()
method. The method takes a mandatory destination
argument corresponding to the STOMP destination. It also takes two optional arguments: headers
, a JavaScript object containing additional message headers and body
, a String object.
client.send("/queue/test", {priority: 9}, "Hello, STOMP");
The client will send a STOMP SEND frame to /queue/test
destination with a header priority
set to 9
and a body Hello, STOMP
.
If you want to send a message with a body, you must also pass the headers
argument. If you have no headers to pass, use an empty JavaScript literal {}
:
client.send(destination, {}, body);
To receive messages in the browser, the STOMP client must first subscribe to a destination.
You can use the subscribe()
method to subscribe to a destination. The method takes 2 mandatory arguments: destination
, a String corresponding to the destination and callback
, a function with one message
argument and an optional argument headers
, a JavaScript object for additional headers.
var subscription = client.subscribe("/queue/test", callback);
The subscribe()
methods returns a JavaScript obect with 1 attribute, id
, that correspond to the client subscription ID and one method unsubscribe()
that can be used later on to unsubscribe the client from this destination.
By default, the library will generate an unique ID if there is none provided in the headers. To use your own ID, pass it using the headers
argument:
var mysubid = '...';
var subscription = client.subscribe(destination, callback, { id: mysubid });
The client will send a STOMP SUBSCRIBE frame to the server and register the callback. Every time the server send a message to the client, the client will in turn call the callback with a STOMP Frame object corresponding to the message:
callback = function(message) {
// called when the client receives a STOMP message from the server
if (message.body) {
alert("got message with body " + message.body)
} else {
alert("got empty message");
}
});
The subscribe()
method takes an optional headers
argument to specify additional headers when subscribing to a destination:
var headers = {ack: 'client', 'selector': "location = 'Europe'"};
client.subscribe("/queue/test", message_callback, headers);
The client specifies that it will handle the message acknowledgement and is interested to receive only messages matching the selector location = 'Europe'
.
If you want to subscribe the client to multiple destinations, you can use the same callback to receive all the messages:
onmessage = function(message) {
// called every time the client receives a message
}
var sub1 = client.subscribe("queue/test", onmessage);
var sub2 = client.subscribe("queue/another", onmessage);
To stop receiving messages, the client can use the unsubscribe()
method on the object returned by the subscribe()
method.
var subscription = client.subscribe(...);
...
subscription.unsubscribe();
The body of a STOMP message must be a String
. If you want to send and receive JSON objects, you can use JSON.stringify()
and JSON.parse()
to transform the JSON object to a String and vice versa.
var quote = {symbol: 'APPL', value: 195.46};
client.send("/topic/stocks", {}, JSON.stringify(quote));
client.subcribe("/topic/stocks", function(message) {
var quote = JSON.parse(message.body);
alert(quote.symbol + " is at " + quote.value);
};
By default, STOMP messages will be automatically acknowledged by the server before the message is delivered to the client.
The client can chose instead to handle message acknowledgement by subscribing to a destination and specify a ack
header set to client
or client-individual
.
In that case, the client must use the message.ack()
method to inform the server that it has acknowledge the message.
var subscription = client.subscribe("/queue/test",
function(message) {
// do something with the message
...
// and acknowledge it
message.ack();
},
{ack: 'client'}
);
The ack()
method accepts a headers
argument for additional headers to acknowledge the message. For example, it is possible to acknowledge a message as part of a transaction and ask for a receipt when the ACK
STOMP frame has effectively be processed by the broker:
var tx = client.begin();
message.ack({ transaction: tx.id, receipt: 'my-receipt' });
tx.commit();
The nack()
method can also be used to inform STOMP 1.1 brokers that the client did not consume the message. It takes the same arguments than the ack()
method.
Messages can be sent and acknowledged in a transaction.
A transaction is started by the client using its begin()
method which takes an optional transaction
, a String which uniquely identifies the transaction. If no transaction
is passed, the library will generate one automatically.
This methods returns a JavaScript object with a id
attribute corresponding to the transaction ID and two methods:
commit()
to commit the transaction abort()
to abort the transactiontransaction
set with the transaction
id
.
// start the transaction
var tx = client.begin();
// send the message in a transaction
client.send("/queue/test", {transaction: tx.id}, "message in a transaction");
// commit the transaction to effectively send the message
tx.commit();
If you forget to add the transaction
header when calling send()
the message will not be part of the transaction and will be sent directly without waiting for the completion of the transaction.
var txid = "unique_transaction_identifier";
// start the transaction
var tx = client.begin();
// oops! send the message outside the transaction
client.send("/queue/test", {}, "I thought I was in a transaction!");
tx.abort(); // Too late! the message has been sent
There are few tests in the code and it is helpful to see what is sent and received from the library to debug application.
The client can set its debug
property to a function with takes a String
argument to see all the debug statements of the library:
client.debug = function(str) {
// append the debug log to a #debug div somewhere in the page using JQuery:
$("#debug").append(str + "\n");
};
By default, the debug messages are logged in the browser window's console.
The source code contains a chat example in examples/chat/index.html
You need to start a STOMP server with support for WebSocket (using for example HornetQ).
Click on the Connect button to connect to the server and subscribe to the /queue/test/
queue.
You can then type messages in the form at the bottom of the page to send STOMP messages to the queue. Messages received by the client will be displayed at the top of the page.
You can also send regular STOMP messages and see them displayed in the browser. For example using directly telnet on STOMP default port:
$ telnet localhost 61613 CONNECT login:guest passcode:guest ^@ CONNECTED session:1092296064
^@ is a null (control-@ in ASCII) byte.
SEND destination:/queue/test Hello from TCP! ^@
You should now have received this message in your browser.
The source code is hosted on GitHub:
git clone git://github.com/jmesnil/stomp-websocket.git