Graphics Programs Reference
In-Depth Information
Accepting web requests on port 80
Got request from 127.0.0.1:52996 "GET / HTTP/1.1"
Opening './webroot/index.html' 200 OK
Got request from 127.0.0.1:52997 "GET /image.jpg HTTP/1.1"
Opening './webroot/image.jpg' 200 OK
Got request from 127.0.0.1:52998 "GET /favicon.ico HTTP/1.1"
Opening './webroot/favicon.ico' 404 Not Found
The address 127.0.0.1 is a special loopback address that routes to the
local machine. The initial request gets index.html from the webserver, which
in turn requests image.jpg. In addition, the browser automatically requests
favicon.ico in an attempt to retrieve an icon for the web page. The screen-
shot below shows the results of this request in a browser.
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Peeling Back the Lower Layers
When you use a web browser, all seven OSI layers are taken care of for you,
allowing you to focus on browsing and not protocols. At the upper layers of
OSI, many protocols can be plaintext since all the other details of the connec-
tion are already taken care of by the lower layers. Sockets exist on the session
layer (5), providing an interface to send data from one host to another.
TCP on the transport layer (4) provides reliability and transport control,
while IP on the network layer (3) provides addressing and packet-level
communication. Ethernet on the data-link layer (2) provides addressing
between Ethernet ports, suitable for basic LAN (Local Area Network)
