Steve,
You are thinking inbound. Yahoo takes inbound port 80, and that prevents
you from opening a Web site located on a Web server running on the same
machine as the Yahoo IM program.
If you make a request for
http://www.jimcoaddins.com, I guarantee you that
it will be on outbound port 80. Why? Because IIS on the Web server is
listening on port 80! If you don't send a request on port 80, the server
won't get it.
Think about it for a minute. As you said, Yahoo IM (in addition to others)
listens on port 80. Therefore, when you try and connect to a Web server on
that machine, FrontPage will tell you that there is no Web server on port
80. Why? Because unless you explicitly indicate otherwise, HTTP is going
to send a request on port 80. That's the way the protocol works.
I'm not sure what/how you captured your traffic data, but if it is
indicating that you are not making a request on outbound port 80, it is not
valid data. Your software may be indicating the src port and not the
destination port. Remember that I said that the response from the server
will be on a random port. That port is the src port and it is the port that
the client will listen on for the response. However, the request is sent on
the destination port 80.
I just captured a Netmon trace of a request for my Web site. Here's what
happened:
GET REQUEST src: 3287 dst: 80
RESPONSE src: 80 dst: 3287
GET src: 3290 dst: 80
RESPONSE src: 80 dst: 3290
This continues on until the page is loaded. In this case, you can see that
the client initiates the request on outbound port 80. The inbound port is
3287. The Web server then sends a response from the source port 80 to the
destination port 3287. 3287 is the current INBOUND port for the client, but
the outbound port is still set to 80 and always must be because that's the
port the server is listening on.
Next the client makes another request on port 80. It sets the src port to
3290 which just tells the server to send the response to that port. The
server on port 80 sends the response to 3290. The next request (not shown
here) from the client changes the port again and it continues on.
This is why people have trouble when they try to answer the question "which
inbound port do I need to open on my firewall so that I can use FrontPage?"
The answer is "every port between 1024 and 5000." Those are the ports that
Wininet (the Microsoft HTTP stack) is going to set as an inbound port for
responses. However, if requesting data from a Web server over the default
HTTP port, the destination port (the port on which the client sends the
request) will be port 80.
--
Jim Cheshire
Jimco Add-ins
http://www.jimcoaddins.com
===================================
Co-author of Special Edition
Using Microsoft FrontPage 2003
Order it today!
http://sefp2003.frontpagelink.com