Posted on 2006-05-17 15:45:37, modified on 2006-05-17 15:54:45
Tags: Networking, Voice over IP, Cisco
The Cisco 7970 phones have a nifty feature: IP Phone Services. With it, you can access services on the internet (for example the stock value of CSCO). I have been asked to make some nifty features, but the phone has some funky HTTP client code.
This is how our services are configured in the Cisco Call Manager
Service URL: http://xml.barnet.com.au/echo.xml
And this it the HTTP request the phone sends
GET /echo.xml?demo=text HTTP/1.1. Host: 202.83.176.80:80. Connection: close. User-Agent: Allegro-Software-WebClient/4.20. Accept: x-CiscoIPPhone/*;version=3.0, text/*,image/png,*/*. Accept-Language: en. Accept-Charset: iso-8859-1. Cookie: ASPSESSIONIDQQSCDATD=IIHNKHFBLCNEAGLMFDIEEIGN.
So despite that the service has the full hostname, the Host line in the HTTP request contains an IP address. It's HTTP/1.1, so the Host line is required. RFC2616 says this about it:
14.23 Host
The Host request-header field specifies the Internet host and port
number of the resource being requested, as obtained from the original
URI given by the user or referring resource (generally an HTTP URL,
as described in section 3.2.2). The Host field value MUST represent
the naming authority of the origin server or gateway given by the
original URL. This allows the origin server or gateway to
differentiate between internally-ambiguous URLs, such as the root "/"
URL of a server for multiple host names on a single IP address.
Host = "Host" ":" host [ ":" port ] ; Section 3.2.2
A "host" without any trailing port information implies the default
port for the service requested (e.g., "80" for an HTTP URL). For
example, a request on the origin server for
<http://www.w3.org/pub/WWW/> would properly include:
GET /pub/WWW/ HTTP/1.1
Host: www.w3.org
A client MUST include a Host header field in all HTTP/1.1 request
messages . If the requested URI does not include an Internet host
name for the service being requested, then the Host header field MUST
be given with an empty value. An HTTP/1.1 proxy MUST ensure that any
request message it forwards does contain an appropriate Host header
field that identifies the service being requested by the proxy. All
Internet-based HTTP/1.1 servers MUST respond with a 400 (Bad Request)
status code to any HTTP/1.1 request message which lacks a Host header
field.
Reading this, it looks like the IP address isn't even allowed there. But it should have been xml.barnet.com.au.
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