AudioCodes Mediant 800 User Manual page 896

CHAPTER 37 Advanced SBC Features
Sec-WebSocket-Accept: rLHCkw/SKsO9GAH/ZSFhBATDKrU=
Sec-WebSocket-Protocol: SIP
Server: SBC
At this stage, the HTTP connection breaks down and is replaced by a WebSocket connection over
the same underlying TCP/IP connection. By default, the WebSocket connection uses the same
ports as HTTP (80) and HTTPS (443).
Once a WebSocket connection is established, the SIP messages are sent over the WebSocket
session. The device, as a "WebSocket gateway" or server can interwork WebSocket browser
originated traffic to SIP over UDP, TCP or TLS, as illustrated below:
The SIP messages over WebSocket are indicated by the "ws" value, as shown in the example
below of a SIP REGISTER request received from a client:
REGISTER sip:10.132.10.144 SIP/2.0
Via: SIP/2.0/WS v6iqlt8lne5c.invalid;branch=z9hG4bK7785666
Max-Forwards: 69
To: <sip:101@10.132.10.144>
From: "joe" <sip:101@10.132.10.144>;tag=ub50pqjgpr
Call-ID: fhddgc3kc3hhu32h01fghl
CSeq: 81 REGISTER
Contact: <sip:0bfr9fd5@v6iqlt8lne5c.invalid;transport=ws>;reg-
id=1;+sip.instance="<urn:uuid:4405bbe2-cf06-4c27-9c59-6caf83af9b00>";expires=600
Allow: ACK,CANCEL,BYE,OPTIONS,INVITE,MESSAGE
Supported: path, outbound, gruu
User-Agent: JsSIP 0.3.7
Content-Length: 0
To keep a WebSocket session alive, it is sometimes necessary to send regular messages to
indicate that the channel is still being used. Some servers, browsers or proxies may close an idle
connection. Ping-Pong WebSocket messages are designed to send non-application level traffic
that prevents the channel from being prematurely closed. You can configure how often the device
pings the WebSocket client, using the WebSocketProtocolKeepAlivePeriod parameter (see
Configuring WebRTC). The device always replies to ping control messages with a pong message.
The WebSocket protocol supports keep-alive using special frames, however it is used only on the
server side; for the Web client, a special ping (CRLF) request is used which the device answers.
In this way the client can detect connection failures
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