HTML and CSS Reference
In-Depth Information
The WebSocket Object
The HTML5
WebSocket
object provides properties, methods, and events that you can use to develop a Web
Socket client application. Table 11-4 shows them for your quick reference.
Table 11-4.
Properties, Methods, and Events of the
WebSocket
Class
Property / Method /
Event
Member
Description
readyState
Property
Read-only property that returns the current state of the
connection. Possible values are
0
(
CONNECTING
),
1
(
OPEN
),
2
(
CLOSING
), and
3
(
CLOSED
).
bufferedAmount
Property
Read-only property that returns the number of bytes of data that
have been queued for transmission over the network.
send()
Method
Sends data to the Web Socket server over an established
connection.
close()
Method
Closes the previously established connection with the Web Socket
server.
open
Raised when the
readyState
property changes to
1
(
OPEN
) and
indicates that the connection is ready to send and receive data.
Event
close
Raised when the
readyState
property changes to
3
(
CLOSED
).
Event
message
Event
Raised when a message is received from the Web Socket server.
error
Event
Raised when an error occurs during communication with the Web
Socket server.
When you create an instance of
WebSocket
, you need to supply the endpoint URL that connects the
client to the Web Socket server. As you can see from Table 11-4, the data-sending and -receiving pattern
used by
WebSocket
is similar to earlier techniques. Once a connection is established, you send data using
send()
as and when required. At the same time, the
message
event-handler function keeps receiving
messages sent by the server.
Using WebSocket in ASP.NET
As mentioned earlier, while developing a Web Socket application you have two distinct pieces of code: the
Web Socket client and the Web Socket server. The Web Socket client is developed using JavaScript and the
HTML5
WebSocket
object. So, this piece of code follows the same coding pattern regardless of your web
server software. However, when you're developing the Web Socket server, you need to use the framework
provided by the web server software and the server-side framework you're using. As far as ASP.NET is
concerned, IIS 8 and certain .NET framework classes together allow you to develop a Web Socket server.
To understand how the client-side and server-side code go hand in hand, let's develop a simple Echo
server that echoes whatever the client sends to it. Although the Echo server doesn't perform simultaneous
two-way communication like a chat application, it does illustrate how the Web Socket client and server
interact. The web form that acts as a Web Socket client is shown in Figure 11-9.
