This repository contains a barebones WebSocket server and client implementation written in 100% Java. The underlying classes are implemented
java.nio, which allows for a non-blocking event-driven model (similar to the WebSocket API for web browsers).
Implemented WebSocket protocol versions are:
Here some more details about protocol versions/drafts.
Dependency management tools
Below is a brief guide to using dependency management tools like maven or gradle.
To use maven add this dependency to your pom.xml:
<dependency> <groupId>org.java-websocket</groupId> <artifactId>Java-WebSocket</artifactId> <version>1.4.0</version> </dependency>
To use Gradle add the maven central repository to your repositories list:
Then you can just add the latest version to your build.
This library uses SLF4J for logging and does not ship with any default logging implementation.
Exceptions are using the log level
ERROR and debug logging will be done with log level
Feel free to use whichever logging framework you desire and use the corresponding binding in your dependency management.
If you want to get started, take a look at the SimpleLogger example.
If you do not use any dependency management tool, you can find the latest standalone jar here.
Writing your own WebSocket Server
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
org.java_websocket.client.WebSocketClient abstract class can connect to valid WebSocket servers. The constructor expects a valid
ws:// URI to connect to. Important events
onError get fired throughout the life of the WebSocketClient, and must be implemented in your subclass.
You can find a lot of examples here.
This library supports wss. To see how to use wss please take a look at the examples.
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. ( https://bugzilla.mozilla.org/show_bug.cgi?id=594502 ).
If the websocket server url is
wss://localhost:8000 visit the url
https://localhost:8000 with your browser. The browser will recognize the handshake and allow you to accept the certificate. This technique is also demonstrated in this video.
The vm option
-Djavax.net.debug=all can help to find out if there is a problem with the certificate.
It is currently not possible to accept ws and wss connections at the same time via the same websocket server instance.
For some reason Firefox does not allow multiple connections to the same wss server if the server uses a different port than the default port (443).
If you want to use
wss on the android platfrom you should take a look at this.
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:
- Java 1.6 and higher
- Android 4.0 and higher
Other JRE implementations may work as well, but haven't been tested.
Everything found in this repo is licensed under an MIT license. See the
LICENSE file for specifics.