WsChatServlet.java

## chat.html
<!DOCTYPE html>
<html>
    <head>
        <meta charset=UTF-8>
        <title>Tomcat WebSocket Chat</title>
        <script>
            var ws = new WebSocket("ws://localhost:8080/TomcatWebSocket/wschat/WsChatServlet");
            ws.onopen = function(){
            };
            ws.onmessage = function(message){
                document.getElementById("chatlog").textContent += message.data + "\n";
            };
            function postToServer(){
                ws.send(document.getElementById("msg").value);
                document.getElementById("msg").value = "";
            }
            function closeConnect(){
                ws.close();
            }
        </script>
    </head>
    <body>
        <textarea id="chatlog" readonly></textarea><br/>
        <input id="msg" type="text" />
        <button type="submit" id="sendButton" onClick="postToServer()">Send!</button>
        <button type="submit" id="sendButton" onClick="closeConnect()">End</button>
    </body>
</html>

## web.xml
<?xml version="1.0" encoding="UTF-8"?>

<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

    <servlet>
        <servlet-name>WsChatServlet</servlet-name>
        <servlet-class>wsapp.WsChatServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>WsChatServlet</servlet-name>
        <url-pattern>/wschat/WsChatServlet</url-pattern>
    </servlet-mapping>

</web-app>

## WsChatServlet.java
//This sample is how to use websocket of Tomcat.
package wsapp;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.util.ArrayList;
import org.apache.catalina.websocket.MessageInbound;
import org.apache.catalina.websocket.StreamInbound;
import org.apache.catalina.websocket.WebSocketServlet;
import org.apache.catalina.websocket.WsOutbound;

public class WsChatServlet extends WebSocketServlet{
    private static final long serialVersionUID = 1L;
    private static ArrayList<MyMessageInbound> mmiList = new ArrayList<MyMessageInbound>();

    public StreamInbound createWebSocketInbound(String protocol){
        return new MyMessageInbound();
    }

    private class MyMessageInbound extends MessageInbound{
        WsOutbound myoutbound;

        @Override
        public void onOpen(WsOutbound outbound){
            try {
                System.out.println("Open Client.");
                this.myoutbound = outbound;
                mmiList.add(this);
                outbound.writeTextMessage(CharBuffer.wrap("Hello!"));
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        @Override
        public void onClose(int status){
            System.out.println("Close Client.");
            mmiList.remove(this);
        }

        @Override
        public void onTextMessage(CharBuffer cb) throws IOException{
            System.out.println("Accept Message : "+ cb);
            for(MyMessageInbound mmib: mmiList){
                CharBuffer buffer = CharBuffer.wrap(cb);
                mmib.myoutbound.writeTextMessage(buffer);
                mmib.myoutbound.flush();
            }
        }

        @Override
        public void onBinaryMessage(ByteBuffer bb) throws IOException{
        }
    }
}