Everything You Need to Know About Using OkHttp Websocket in Android

Introduction

Websockets are becoming increasingly popular in the world of web development. They provide a two-way communication channel between the client and the server, which is essential for real-time applications such as online gaming, chat applications, and stock market updates. OkHttp is a popular HTTP client for Android that provides support for websockets. In this article, we will discuss everything you need to know about using OkHttp websocket in Android.

What is OkHttp?

OkHttp is an open-source HTTP and HTTP/2 client for Android and Java applications. It is developed by Square and is widely used in the Android community. OkHttp is easy to use, efficient, and provides support for websockets. It is built on top of the Java URLConnection API, which provides a low-level interface for interacting with HTTP and HTTPS servers.

Features of OkHttp

Support for HTTP/2, which provides significant performance improvements over HTTP/1.1.
Support for websockets, which provides a two-way communication channel between the client and the server.
Transparent GZIP compression, which reduces the size of HTTP responses.
Connection pooling, which reduces the overhead of creating new connections to the server.
Caching, which reduces the number of requests to the server and improves performance.

What is Websocket?

Websocket is a protocol that provides a two-way communication channel between the client and the server. It is designed for real-time applications that require frequent updates, such as online gaming, chat applications, and stock market updates. Websocket provides a persistent connection between the client and the server, which allows data to be sent in both directions without the need for a new HTTP request.

How Websocket Works

Websocket is based on the WebSocket API, which provides a low-level interface for interacting with websockets. The WebSocket API is implemented by most modern web browsers, which allows web applications to use websockets without the need for additional plugins or libraries.

Websocket uses a handshake process to establish a connection between the client and the server. The handshake process consists of an HTTP request from the client to the server, followed by an HTTP response from the server to the client. Once the handshake process is complete, the connection is established, and data can be sent in both directions.

Using OkHttp Websocket in Android

OkHttp provides support for websockets through the WebSocket class. The WebSocket class provides a high-level interface for interacting with websockets and is easy to use. To use the WebSocket class, you need to create an instance of the OkHttpClient class and use it to create an instance of the WebSocket class.

Creating an Instance of OkHttpClient

The OkHttpClient class is the main entry point for using OkHttp. To create an instance of OkHttpClient, you can use the following code:

OkHttpClient client = new OkHttpClient();

The above code creates a new instance of OkHttpClient with default settings.

Creating an Instance of WebSocket

To create an instance of WebSocket, you need to provide a request object that specifies the URL of the websocket endpoint. The following code creates a new request object:

Request request = new Request.Builder().url(“ws://example.com/socket“).build();

The above code creates a new request object with the URL of the websocket endpoint.

Once you have created the request object, you can use it to create an instance of WebSocket:

WebSocket websocket = client.newWebSocket(request, new WebSocketListener() {
     @Override
     public void onOpen(WebSocket webSocket, Response response) {
         // Connection opened
     }
     @Override
     public void onMessage(WebSocket webSocket, String text) {
         // Text message received
     }
     @Override
     public void onClosing(WebSocket webSocket, int code, String reason) {
         // Connection closing
     }
     @Override
     public void onClosed(WebSocket webSocket, int code, String reason) {
         // Connection closed
     }
     @Override
     public void onFailure(WebSocket webSocket, Throwable t, Response response) {
         // Connection failed
     }
});

The above code creates a new instance of WebSocket with a WebSocketListener, which provides callback methods for handling events such as connection opened, message received, and connection closed.

Handling Events with WebSocketListener

The WebSocketListener interface provides callback methods for handling events such as connection opened, message received, and connection closed. The following methods are available:

onOpen(WebSocket webSocket, Response response): Called when the connection is opened.
onMessage(WebSocket webSocket, String text): Called when a text message is received.
onClosing(WebSocket webSocket, int code, String reason): Called when the connection is closing.
onClosed(WebSocket webSocket, int code, String reason): Called when the connection is closed.
onFailure(WebSocket webSocket, Throwable t, Response response): Called when the connection fails.

Example Usage of WebSocketListener

The following code shows an example usage of WebSocketListener:

WebSocketListener listener = new WebSocketListener() {
     @Override
     public void onOpen(WebSocket webSocket, Response response) {
         // Connection opened
     }
     @Override
     public void onMessage(WebSocket webSocket, String text) {
         // Text message received
         System.out.println(“Received message: ” + text);
     }
     @Override
     public void onClosing(WebSocket webSocket, int code, String reason) {
         // Connection closing
     }
     @Override
     public void onClosed(WebSocket webSocket, int code, String reason) {
         // Connection closed
     }
     @Override
     public void onFailure(WebSocket webSocket, Throwable t, Response response) {
         // Connection failed
     }
};

The above code creates a new instance of WebSocketListener and provides implementations for the callback methods.

Sending and Receiving Messages with WebSocket

Once the connection is established, you can send and receive messages using the WebSocket.send() and WebSocket.close() methods. The send() method is used to send messages to the server, while the close() method is used to close the connection.

Sending Messages

You can send messages using the send() method. The following code sends a text message:

websocket.send(“Hello, server!”);

The above code sends a text message to the server.

Receiving Messages

You can receive messages using the onMessage() method of the WebSocketListener interface. The following code shows an example implementation of onMessage() method:

@Override
public void onMessage(WebSocket webSocket, String text) {
System.out.println(“Received message: ” + text);
}

The above code prints the received message to the console.

FAQ

What is OkHttp?

OkHttp is an open-source HTTP and HTTP/2 client for Android and Java applications. It provides support for websockets and is easy to use.

What is Websocket?

How to use OkHttp websocket in Android?

To use OkHttp websocket in Android, you need to create an instance of OkHttpClient and use it to create an instance of WebSocket. You can then use the WebSocket.send() and WebSocket.close() methods to send and receive messages.

What are the features of OkHttp?

OkHttp provides support for HTTP/2, websockets, transparent GZIP compression, connection pooling, and caching.

What are the callback methods provided by WebSocketListener?

The WebSocketListener interface provides callback methods for handling events such as connection opened, message received, and connection closed. The available methods are onOpen(), onMessage(), onClosing(), onClosed(), and onFailure().

What is the WebSocket API?

The WebSocket API provides a low-level interface for interacting with websockets. It is implemented by most modern web browsers, which allows web applications to use websockets without the need for additional plugins or libraries.

What is the difference between HTTP and Websocket?

HTTP is a request-response protocol, while Websocket is a two-way communication protocol. HTTP requires a new request for each response, while Websocket provides a persistent connection between the client and the server.