Channel API Javascript Reference (Java)
Use the following reference when building JavaScript clients for the channel API.
Building your JavaScript client
Include the following in your html page before any JavaScript code that refers to it:
<script type="text/javascript" src="/_ah/channel/jsapi"></script>
All other JavaScript code must be between the
<body>
tags of the page. For best performance, place your JavaScript code at the bottom of your HTML markup just before the
</body>
.
goog.appengine.Channel() Class
Constructors
goog.appengine.Channel(token)
-
Create a channel object using the token returned by the
createChannel()call on the server.
Methods
open(optional_handler)
-
Open a socket on this channel.
open()returns agoog.appengine.Socketobject. You can set the callback properties directly on the returned socket object or set them using an optional object handler with the following properties:-
onopen -
onmessage -
onerror -
onclose
If the token specified during channel creation is invalid or expired then the
onerrorandonclosecallbacks will be called. Thecodefield for the error object will be 401 (Unauthorized) and thedescriptionfield will be'Invalid+token.'or'Token+timed+out.'respectively. Theonerrorcallback is also called asynchronously whenever the token for the channel expires. Anonerrorcall is always followed by anonclosecall and the channel object will have to be recreated after this event. -
goog.appengine.Socket() Class
Methods
close()
- Close the socket. The socket cannot be used again after calling close; the server must create a new socket.
Properties
onopen
- Set this to a function called when the socket is ready to receive messages.
onmessage
-
Set this to a function called when the socket receives a message. The function is passed one parameter: a message object. The
datafield of this object is the string passed to thesend_messagemethod on the server.
onerror
-
Set this property to a function called when an error occurs on the socket. The function is passed one parameter: an error object. The
descriptionfield is a description of the error and thecodefield is an HTTP error code indicating the error.
onclose
-
Set this property to a function that called when the socket is closed. When the socket is closed, it cannot be reopened. Use the
open()method on agoog.appengine.Channelobject to create a new socket.