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From André Warnier>
Subject Re: [OT?] Virtual hosting - does the port need to match the URL port?
Date Tue, 17 May 2011 23:31:58 GMT
Hassan Schroeder wrote:
> On Tue, May 17, 2011 at 3:35 PM, André Warnier <> wrote:
>> (RFC 2616 says that a port can be present in the Host: header; but it does
>> not mention what the server should do with it.  And I can't think of what it
>> could do with it either, since by the time the server reads this header, the
>> connection is already established with the webserver anyway.)
> While I haven't run across that port # in the Host header bit before,
> it's possible that the initial server (localhost in the example above)
> is a proxy server, yes?
> In which case the request endpoint could be another (virtual) host,
> on a different port.
> Not that that's probably relevant in this case, but FWIW  :-)
Well, see HTTP RFC 2616 for that, section 5.1.2 Request-URI.

It is a bit confusing, but as I understand it, it is in the first request line that one 
should specify the absolute URI for the request. Like in the example given :


So, supposing that for the browser, the proxy server is, and 
that the browser really wants the resource at,

1) the browser would establish a connection to ""
2) over that connection, it would send the request :


(because the proxy server "" may just be one of the virtual 
hosts running on that machine).

But then, section 5.2 The Resource Identified by a Request, says :

  An origin server that does differentiate resources based on the host requested 
(sometimes referred to as virtual hosts or vanity host names) MUST use the following rules

for determining the requested resource on an HTTP/1.1 request:

1. If Request-URI is an absoluteURI, the host is part of the Request-URI. Any Host header

field value in the request MUST be ignored.
2. If the Request-URI is not an absoluteURI, and the request includes a Host header field,

the host is determined by the Host header field value.
3. If the host as determined by rule 1 or 2 is not a valid host on the server, the 
response MUST be a 400 (Bad Request) error message.

(while not forgetting that contrarily to what I was thinking, according to Konstantin 
Tomcat actually parses and uses the :port element provided in the Host: header, at least 
apparently to pass it as information to the webapp.)
(But since Tomcat, as far as I know, cannot act as a proxy server, these subtle 
distinctions may be moot anyway).


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