why dwr is asynchronous ？what's wrong

i open 2 web pages.(http://localhost/chat/test.jsp)
i send message through the first page,but the second cannot receive it immediately.
only when i send message through the second one ,i can receive the message the first page has sended.
how can i do

test.jsp

chat.js

Chat.java

package mychat;

import java.text.SimpleDateFormat;
import java.util.Collection;
import java.util.Date;
import java.util.LinkedList;

import org.directwebremoting.*;
import org.directwebremoting.annotations.RemoteMethod;
import org.directwebremoting.annotations.RemoteProxy;
import org.directwebremoting.annotations.ScriptScope;

@RemoteProxy(scope=ScriptScope.APPLICATION)
public class Chat  {

public Chat() {
		super();
		// TODO Auto-generated constructor stub
//		Util.execute(this);
	}

@RemoteMethod
//	public  void send(final String sendMessage) {   //i have tried 2 methods,but failed.
//		String ip=WebContextFactory.get().getHttpServletRequest().getLocalAddr();
//		final MessageInformation mi=new MessageInformation(ip,sendMessage,new SimpleDateFormat("h:mm a").format(new Date()).toString());
//		Browser.withCurrentPage((new Runnable() {
//			public void run() {
//				System.out.println(mi);
//				ScriptSessions.addFunctionCall("update", mi);
//			}
//		}));
//	}
	public  void send(final String sendMessage) {
		String ip=WebContextFactory.get().getHttpServletRequest().getLocalAddr();
		final MessageInformation mi=new MessageInformation(ip,sendMessage,new SimpleDateFormat("h:mm a").format(new Date()).toString());
			Browser.withCurrentPage(new Runnable() {
			public void run() {
			ScriptBuffer script = createMyScriptBuffer(mi);
			Collection<ScriptSession> sessions = Browser.getTargetSessions();
			for (ScriptSession scriptSession : sessions) {
				System.out.println(script);
				scriptSession.addScript(script);	
			}	
			}
		});
	}
	private ScriptBuffer createMyScriptBuffer(MessageInformation messageInformation) {
		// TODO Auto-generated method stub
	
	String str="var last=dwr.util.getValue(\"content\");"+
	"if(!isEmpty(last)){"+
	"	last+=\"\n\";"+
	"}"+
	"var totalMessage="+messageInformation.ip+":"+messageInformation.message+"\n"+"  "+messageInformation.date+";"+
	"dwr.util.setValue(\"content\",last+totalMessage);";
	return new ScriptBuffer().appendCall("update", messageInformation);
	
	}
}