86 lines
4.6 KiB
Markdown
86 lines
4.6 KiB
Markdown
---
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banner_title: "Flash - Websockets"
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banner_description: "Learn how to create and manage server-side Websockets in Flash."
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---
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# 🌐 Websockets
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In this section, we illustrate how to create and manage Websockets in Flash, which are used to establish a bidirectional communication channel between the client and the server.
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## Understanding Websockets
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Websockets are a communication protocol that provides full-duplex communication channels over a single TCP connection.
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Unlike HTTP, which is a request-response protocol, Websockets allow for real-time, low-latency communication between the client and the server.
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Imagine a scenario where you need to send real-time updates to the client, such as a chat application or a live feed: if you were to use HTTP,
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you would need to poll the server at regular intervals to check for updates, which is inefficient and resource-intensive.
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## Creating a Websocket
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To create a Websocket in Flash, you need to extend the `WebsocketHandler` class and override the `onOpen`, `onMessage`, `onClose`, and `onError` methods.
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These methods are called when the Websocket connection is opened, a message is received, the connection is closed, and an error occurs, respectively,
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and they provide you with an instance of the `WebSocketSession` object to be able to interact with it.
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```java
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public class MyWebsocketHandler extends WebsocketHandler {
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@Override
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public void onOpen(WebSocketSession session) {
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System.out.println("WebSocket connection opened");
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}
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@Override
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public void onClose(WebSocketSession session, int statusCode, String reason) {
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System.out.println("WebSocket connection closed");
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}
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@Override
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public void onMessage(WebSocketSession session, String message) {
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System.out.println("Received message: " + message);
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//optionally send a reponse back to the client
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session.sendMessage("I received your message!");
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}
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@Override
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public void onError(WebSocketSession session, Throwable error) {
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System.out.println("WebSocket error: " + error.getMessage());
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}
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}
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```
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To register your Websocket handler with the server, you can use the `server.ws()` method:
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```java
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public class Example {
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public static void main(String[] args) {
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FlashServer server = new FlashServer(8080);
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server.ws("/ws")
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.register(new MyWebsocketHandler());
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server.start();
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}
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}
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```
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## Interacting with Websockets sessions
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The `WebSocketSession` object provides methods to interact with the Websocket session, such as sending messages, closing the connection, and getting the remote address and session ID.
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| Method | Params | Description |
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|--------------------|------------------|--------------------------------------------------------------------------------------------------------------------------------------------------|
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| `getChannel()` | `none` | Returns an instance of `AsynchronousSocketChannel` useful for retrieving info about the client . |
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| `getRequestInfo()` | `none` | Returns an instance of `RequestInfo` containing all sorts of information about the request (headers, method, path etc.) . |
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| `getPath()` | `none` | Returns the path to the websocket endpoint as a `String`. |
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| `getId()` | `none` | Returns the id of the websocket session as a `String`, useful if you want to keep track of the connected clients in a custom manager. |
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| `getBuffer()` | `none` | Returns the ByteBuffer for that session. |
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| `sendMessage()` | `String message` | Sends the `message` to the client as a `String`. it's up to the developer to stringify and de-stringify any data you want to send back and forth |
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| `close()` | `none` | Closes the websocket session. |
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::: warning NOTE
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`WebsocketHandler` includes a `setId(String id)` method for overriding the default session ID. Unless you have a specific reason to change it, it's best to leave it as is.
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Similarly, the `setBuffer(ByteBuffer buffer)` method allows you to override the default buffer. If you're unsure about this, it's recommended to keep the default setting.
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:::
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