This project contains different examples of the use of Websockets (see below chapters for explanations of each example).

NOTE: All the following examples make use of an embedded web server, the Jetty server. This server is included as a dependency library in gradle (see build.gradle), and it's needed for all the tests to work.

The classes com.ilozanof.learning.websocket.WebsocketHttpServer.java and com.ilozanof.learning.websocket.WebsocketSecureServer.java take care of running this server, and it's used by all the Tests in this project.

In this example, we have:

• 1 Endpoint in the Server. It keeps track of all the Sessions opened by different clientes, and for each Message it receives, it sends it back to ALL the clients (including the one who sent it).
• 1 Java Client that sends messages and also works as a Listener for incoming messags from the Server.
• 1 Web Client, implemented in (HTML + CSS + JS + jQuery). The source code is composed of the following files:
  • broadcastClient.html: The HTML containing the user interface
  • *clientCommon.css": Commons styles for all the examples in this project.
  • *clientCommon.js": Commons JS functions
  • messageHandling.js": Implementation of functions responsible for encoding/decoding messages from/to the WebSocket.

Just run the tests.

In this case, we need to run the Server first, and then test the HTML pages. And depending on whether we are testing HTTP or SSL, there are some minor things that we need to be aware of:

Nothing special needs to be done here, since both Server implementations (WebsocketHttpSever and WebsocketSecureServer) include HTTP support in the port 8080. So open the file src/main/resources/webClient/broadcastClient.html file in a web browser, that will show the Client pre-configured for HTTP. Now you can type and send messages, and they will be displayed below in the page, after being sent to the Server and back to the client. You can open different browsers at the same time, to check that the messages are broadcasted to all of them...

• NOTE: If you try to select SSL in the Web client, you'll get an error due to the certificate this example is using. To fix that issue, go to the next chapter.

If you try to select the SSL option in the example from the previoopus chapter, you will get an error. In order to enable SSL you must do the following:

1. Make sure that the Server is NOT running (make sure the WebsocketHttpServer class has stopped).
2. Run the WebsocketSecureServer class.
3. Open the file src/main/resources/webClient/broadcastClient.html file in a Web browser. DO NOT select the SSL option yet.
4. the SSL option triggers an error because the SSL Server is configured with a self-signed certificate, which might be fine for testing purposes, but it will trigger an error unless we tell the browser to trust that certificate. So in order to do that:
   1. Open a new Tab in the same browser
   2. Type the url: https://localhost:8443. This will show an Alert window, saying that you are accessing a page signed with a non trusted certificate. The way forward here might depend on the browser: in Chrome, click on "Advanved", and then on "Proceed to 127.0.0.1 (unsafe)". This will make the browser trust our test certificate.
   3. Go back to the src/main/resources/webClient/broadcastClient.html file asn refresh.

This example provides the same functionality as the previous one, but in this case the information exchange between the client and the server is NOT plain text, but a Message object.

All the explanations for the previous example also apply for this one, with some additions in the form of:

• A new Message class implementing the Messages exchanged, for example:

Message structure (3 fields):

• from: "a Java client/machine/browser, etc"
• content: "Hi, this is a message"
• version: "1.0"

• Encoders and decoders in the Server side for Message objects.

All the guidelines explained for the Broadcast client also apply here.