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may send all sorts of messages and need a way to identify what they are so you can
process them.
Once we have configured our PublicMessageEvent with the roomId , the zoneId , and the
EsObject , we call es.engine.send(pmr) to send it to the rest of the room:
function sendMessage(event) {
var formElement = document.getElementById("textBox");
var pmr = new PublicMessageRequest();
pmr.message = "";
pmr.roomId =;
pmr.zoneId = _room.zoneId;
var esob = new ElectroServer.EsObject();
esob.setString("message", formElement.value);
pmr.esObject = esob;
statusMessages.push("message sent")
Notice that we did not print the user's chat message to the canvas when it was sub-
mitted. Instead, we will wait for the PublicMessageEvent to return from Electro
Server , and then handle it like all the other chats. This keeps the interface clean, while
preserving a create event/handle event processing model across the entire application.
After the socket server processes the chat message, it is broadcast out to all the users
in the room. All the users must create an event handler for a PublicMessageEvent so
they can receive and process the message; we have created the onPublicMessageEvent
handler for this purpose. This function is very simple. It checks the type EsObject
variable we set to see whether it is a chatmessage . If so, it pushes a string that includes
the user who submitted the message ( event.userName ) and the message itself ( esob.get
String("message") ) into the chatMessages array. This is what will be displayed on the
function onPublicMessageEvent(event) {
var esob = event.esObject;
statusMessages.push("message received")
if (esob.getString("type") == "chatmessage") {
chatMessages.push(event.userName + ":" + esob.getString("message"));
Now, all that remains is to display the messages that we have collected. We do this
(where else?) in drawScreen() . For both the statusMessages and chatMessages arrays,
we need to display the “current” 22 messages (if we have 22 ), and start them at the y
position of 15 pixels. We only display the last 22 messages so both the chat and the
status messages will appear to scroll up the screen as more chatting and status messages
are generated:
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