A barebones WebSocket client and server implementation written in 100% Java.

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Java WebSockets

This repository contains a barebones WebSocket server and client implementation written in 100% Java. The underlying classes are implemented using the Java ServerSocketChannel and SocketChannel classes, which allows for a non-blocking event-driven model (similar to the WebSocket API for web browsers).

Implemented WebSocket protocol versions are:

Running the Example

There's a simple chat server and client example located in the example folder. First, compile the example classes and JAR file:


Then, start the chat server (a WebSocketServer subclass):

java -cp build/examples:dist/WebSocket.jar ChatServer

Now that the server is started, we need to connect some clients. Run the Java chat client (a WebSocketClient subclass):

java -cp build/examples:dist/WebSocket.jar ChatClient

Note: If you're on Windows, then replace the : (colon) in the classpath in the commands above with a ; (semicolon).

The chat client is a simple Swing GUI application that allows you to send messages to all other connected clients, and receive messages from others in a text box.

There's also a simple HTML file chat client chat.html, which can be opened by any browser. If the browser natively supports the WebSocket API, then it's implementation will be used, otherwise it will fall back to a Flash-based WebSocket Implementation.

Writing your own WebSocket Server

The org.java_websocket.server.WebSocketServer abstract class implements the server-side of the WebSocket Protocol. A WebSocket server by itself doesn't do anything except establish socket connections though HTTP. After that it's up to your subclass to add purpose.

Writing your own WebSocket Client

The org.java_websocket.server.WebSocketClient abstract class can connect to valid WebSocket servers. The constructor expects a valid ws:// URI to connect to. Important events onOpen, onClose, onMessage and onIOError get fired throughout the life of the WebSocketClient, and must be implemented in your subclass.

WSS Support

WSS support is still VERY young ( ). The only way to use wss is currently the one shown in the example. That also means that you have to switch between ws and wss. You can not have both at the same time on the same port.

If you do not have a valid certificate in place then you will have to create a self signed one. Browsers will simply refuse the connection in case of a bad certificate and will not ask the user to accept it. So the first step will be to make a browser to accept your self signed certificate. ( ) If the websocket server url is wss://localhost:8000 visit the url htts://localhost:8000 with your browser. The browser will recognize the handshake and allow you to accept the certificate.

I ( @Davidiusdadi ) would be glad if you would give some feedback whether wss is working fine for you or not.

Minimum Required JDK

Java-WebSocket is known to work with:

Other JRE implementations may work as well, but haven't been tested.

Testing in Android Emulator

Please note Android Emulator has issues using IPv6 addresses. Executing any socket related code (like this library) inside it will address an error Bad address family

You have to manually disable IPv6 by calling

java.lang.System.setProperty("", "false");
java.lang.System.setProperty("", "true");

somewhere in your project, before instantiating the WebSocketClient class. You can check if you are currently testing in the Android Emulator like this

if ("google_sdk".equals( Build.PRODUCT )) {
  // ... disable IPv6

Getting Support

If you are looking for help using Java-WebSocket you might want to check out the #java-websocket IRC room on the FreeNode IRC network.


Everything found in this repo is licensed under an MIT license. See the LICENSE file for specifics.