- Android java websocket client
- Java WebSocket Programming with Android and Spring Boot
- Android WebSocket Client
- Connect the Client to the Server
- Send Messages to the Server
- Spring Boot WebSocket Server
- Handle the WebSocket Messages
- Configure the WebSocket Request Handling
- Send Data between Server and Client
- Update the Android Client to Pub/Sub
- Modify the Android Client
- Send Data Between Clients
- Android java websocket client
Android java websocket client
WebSockets are an alternative to HTTP communication in Web Applications. They offer a long lived, bidirectional communication channel between client and server. Once established, the channel is kept open, offering a very fast connection with low latency and overhead.
HTTP is a very different protocol, and also a different way of communicate. HTTP is a request/response protocol: the server returns some data when the client requests it.
- the server can send a message to the client without the client explicitly requesting something
- the client and the server can talk to each other simultaneously
- very little data overhead needs to be exchanged to send messages. This means a low latency communication.
WebSockets are great for real-time and long-lived communications. HTTP is great for occasional data exchange and interactions initiated by the client.
Always use the secure, encrypted protocol for WebSockets, wss:// . ws:// refers to the unsafe WebSockets version (the http:// of WebSockets), and should be avoided for obvious reasons.
Let’s use Tornado as Server and nv-websocket-client as WebSocket client for Android.
We are going to update the AndroidManifest.xml file by adding the following user permissions
Add nv-websocket-client dependencies to your project dependencies by adding the following lines in your build.gradle and syncing the project:
Following is a example of WebSocket client for Android.
Socket.IO-client Java is the Socket.IO v1.x Client Library for Java, which is simply ported from the JavaScript client.
Create server as described here.
We are going to update the AndroidManifest.xml file by adding the following user permissions
Add socket.io-client dependencies to your project dependencies by adding the following lines in your build.gradle and syncing the project:
Following is a example of Socket.IO client for Android.
- Socket class implements client sockets
- ServerSocket class implements server sockets. A server socket waits for requests to come in over the network.
- Autobahn|Java is a client library providing WAMP on Java 8 (Netty) and Android, plus (secure) WebSocket for Android.
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Java WebSocket Programming with Android and Spring Boot
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The WebSocket protocol provides an always-on connection between a client and a server for bi-directional communication. This is great for applications that require a real-time connection, such as multiplayer games, internet of things applications, and chat apps. In this tutorial, we are going to set up a simple Android client that will connect to a WebSocket server using Spring Boot.
Android WebSocket Client
For the Android client, we are going to make a simple demo app that contains four image buttons of cute animals. To get started, initialize a new project on Android Studio, with a Basic Activity, called JavaWebSocketClient. We are going to use a lightweight WebSocket client library for the app, which can be found in this repo. In order to use this library, we have to add it to the build.gradle file in the app directory. Add the following to the dependencies and sync the project:
Make sure to include the internet access permission in the manifest file:
Connect the Client to the Server
Go to MainActivity.java, import the following packages and set up onCreate():
Next, create a new method createWebSocketClient():
This may look like a lot, but really, we are doing four key things in this method:
- Starting a new connection to the localhost “ws://10.0.2.2:8080/websocket”.
- Sending a message to the server once a connection is opened.
- Displaying the messages sent from the server on the app.
- Setting timeouts and automatic reconnection.
Now that we connected the client to the server, let’s set up the method to send messages to the server.
Send Messages to the Server
In MainActivity.java, add the following to sendMessage():
When a button is pressed, the button id is sent to the server. This method is called from the file animal_sounds.xml, which you can get from my Java WebSocket Programming Repo. Make sure to modify the file strings.xml under the values directory so you won’t get any errors in the XML file.
The last thing to do on the client-side is to add the images for the animals in the drawable directory. The images are made by Freepik from www.flaticon.com.
Run the Android app in your emulator:
Nothing happens right now because the server is not set up. Let’s do that right now!
Spring Boot WebSocket Server
For our server, we will use Spring Boot which makes it easy to create production-grade Spring applications with minimum configurations. To quickly bootstrap our project, we will use Spring Initializr. We will generate a Gradle project, but you can also generate a Maven project if you prefer. Configure the Initializr like the screenshot below and make sure to add WebSocket as a dependency:
Generate the project to download a zip file. Once you unzip the file, go to the src directory and keep on clicking the subdirectories until you get to the JavaWebSocketServerApplication.java file.
Add two files to the directory: WebSocketHandler.java and WebSocketConfiguration.java.
Handle the WebSocket Messages
We have to handle the incoming messages that arrive in the server. To do so, in WebSocketHandler.java inherit the class to implement the method handleTextMessage(). Add the following code to the file:
Inside the method, we simply get the string value of the message payload and do a switch expression to check the value of the message with the value of each case. A unique message with the animal sound is sent to the client.
Configure the WebSocket Request Handling
In WebSocketConfiguration.java, implement the interface WebSocketConfigurer and add the following code to the file:
We set up the method registerWebSocketHandlers to configure the WebSocketHandler to the path “/websocket“.
That is all for the server-side. Now that we have everything set up, let’s start the WebSocket server and run the app!
Send Data between Server and Client
In the terminal, go to the root directory of your Spring Boot project and run the following command to start the server:
Next, run the Android client in Android Studio and once the app loads, click any of the four buttons.
Play around with the Android app and see how messages are sent from client-to-server with WebSockets!
Update the Android Client to Pub/Sub
Sending data client-to-server or server-to-client is not difficult and can be done pretty fast. But what if you want to send data client-to-client? You can’t directly connect clients without implementing some routing and broker logic on the server.
There are several tools we can use to make this task less time-consuming. One such tool is Socket.IO, which sets up a real-time, bidirectional connection between clients. This is a great open-source tool to use, but we still need to set up a server and connect the client to the server. Is there an easier way to securely and reliably send data between clients without manually setting up a server? With PubNub, we can.
PubNub provides the real-time infrastructure to power any device that speaks TCP. We can stream data from client-to-client, client-to-server or server-to-client using PubNub’s Global Data Stream Network in under 100 ms! With PubNub, an always-on connection is made between the devices connected to the channel, similar to WebSockets. The best part is that you don’t have to worry about setting up a server and maintaining the server because PubNub is serverless and is infinitely scalable.
To see how PubNub simplifies the process of sending data from client-to-client, we will modify the Android app we built earlier. But first, sign up for a free PubNub account to get your free Pub/Sub API keys. Sign up and log in using the form below:
Modify the Android Client
To differentiate the updated app from the old app, create a new Android project called PubNubJavaClient. In order to use PubNub’s Android SDK, add the following to the build.gradle file in the app directory and sync the project:
Include the following permissions to the manifest file:
Everything else, except MainActivity.java, is the same. From the previous app, add the following files to the updated app: animal_sounds.xml, strings.xml and the images from the drawable directory. Once you finish this, go to MainActivity.java to add the new code. Import the following packages and set up onCreate():
Make a call to initPubNub() to initialize PubNub:
We do three key things in this method:
- Initialize the PubNub client API. Make sure to replace “ENTER_YOUR_PUB_KEY” and “ENTER_YOUR_SUB_KEY” with your Pub/Sub keys.
- Set up a listener to get notified of messages that arrive on the channel. As we did earlier, display the message on the app for the client to see.
- Subscribe to the global channel where messages will be published.
When the user presses a button, the method sendMessage() is called:
This method is similar to what we did earlier, except now we publish the actual message, the animal sound, to the global channel and not the server. We use publishMessage() as a helper function to publish the message.
That is all we need to get the app up-and-running!
Send Data Between Clients
Run the Android app in two emulators to see messages appear in real time.
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Android java websocket client
Java/Android WebSocket Client
A very lightweight WebSocket client library for Java/Android which aims to implement the WebSocket protocol as defined in RFC 6455.
This library is published into JCenter and Maven Central.
This is an example of how you can start a new connection.
If you don’t specify a port into the URI, the default port will be 80 for ws and 443 for wss.
This is the list of the default HTTP Headers that will be included into the WebSocket client handshake
- Host
- Upgrade
- Connection
- Sec-WebSocket-Key
- Sec-WebSocket-Version
If you wish to include more headers, like Origin, you can add them using addHeader(String key, String value) method.
You can also override the default SSLSocketFactory using setSSLSocketFactory(SSLSocketFactory factory) .
When an Exception occurs, the library calls onException(Exception e) .
When you are finished using the WebSocket, you can call webSocketClient.close() to close the connection.
Automatic reconnection is supported through enableAutomaticReconnection(long waitTimeBeforeReconnection) method. Every time an IOException occurs, onException(Exception e) method is called and automatically a new connection is created and started. For performance reasons, between every reconnection intent you should specify a wait time before trying to reconnect again, using waitTimeBeforeReconnection parameter.
Connect and read timeouts are supported through setConnectTimeout(int connectTimeout) and setReadTimeout(int readTimeout) . If one of those timeouts expires, onException(Exception e) is called. If automatic reconnection is enabled, a new connection could be established automatically.
Connect timeout is used in establishing a TCP connection between this client and the server. Read timeout is used when this WebSocket Client doesn’t received data for a long time. A server could send data periodically to ensure that the underlying TCP connection is not closed unexpectedly due to an idle connection, and this read timeout is designed for this purpose.
This library supports secure and insecure WebSockets. You just need to define the scheme as wss or ws (case-sensitive) into the URI.
Ping and Pong frames
When a Ping frame is received, automatically a Pong frame is sent with the same Application Data of the Ping frame. You can also send Ping and Pong frames unsolicited using sendPing(byte[] data) and sendPong(byte[] data) . Data can be null if don’t want to send Application Data.
You need Gradle to build the project. Any version will do.
Then you cand find a .jar file inside the build/libs folder
If you want to open the project in Eclipse, just type
and Gradle will automatically generate the source files required to open the project in Eclipse.
If you want to open the project in IntelliJ IDEA, just type
and Gradle will automatically generate the source files required to open the project in IntelliJ IDEA.
This libary requires at minimum Java 1.6 or Android 1.6 (API 4)
Copyright 2017 Gustavo Avila
Licensed under the Apache License, Version 2.0 (the «License»); you may not use this file except in compliance with the License. You may obtain a copy of the License at
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an «AS IS» BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
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