What Takes place from Server to Web Browser
Every time you
good read click on a link in a net web page or variety an address into your net browser you are making a 'request' for a specific document. That request is handled with the Hyper Text Transfer Protocol (HTTP) and sent more than the World wide web to the server which holds the document in question. If all goes effectively the server responds by sending the document -- typically a net web page of text and graphics.
HTTP is element of the Net Protocol (IP) suite. It is utilized by a 'client' such as a internet browser to establish a connection with the server which hosts a specific website. The server waits for incoming requests by monitoring TCP port 80.
Transmission Handle Protocol (TCP) is utilised to create connections amongst two computer systems on the Internet so they can exchange data. TCP has provisions for identifying the requesting laptop or computer and for transmitting data with time stamps so that it can be reassembled in the proper order as soon as it arrives at its destination.
There are several TCP ports which have standardized utilizes. TCP port 21, for example, is normally reserved for FTP (File Transfer Protocol) for uploading and downloading files. Port 80 is typically utilised for HTTP.
If the server receives a request string on TCP port 80 in the type of GET / HTTP/1.1 it will send a response code dependent on whether or not the requested net web page is readily available or not. A typical request goes like this:
GET /faq.html HTTP/1.1
Host: is a request for The 'Host' needs to be specified to distinguish sites which are hosted on shared servers. If faq.html is available the server will respond:
HTTP/1.1 200 OK
Date: Mon, 12 October 2005 22:38:34 GMT
Server: Apache/1.3.27 (Unix) (Red-Hat/Linux)
Last-Modified: Wed, 08 Jan 2003 23:11:55 GMT
...followed by the actual web page.
HTTP/1.1 200 OK signifies that the
the guide to click here requested internet page is accessible. Other codes can also be returned. The code 404, for instance, signifies that the server can't discover the requested page. The internet web page is sent by way of TCP as a series of data packets each with a header that specifies its destination and order in the data stream. The numerous packets can all take different paths to reach their destination. Every is sent by way of a router which polls other routers which are close by. If a connection with the very first router is unavailable the data will be sent by means of one more one particular.
As the data is received the client (the web browser) sends back an acknowledgement. This ensures that all the packets are received within a particular time. If not, they will be re-transmitted by the server. TCP also checks that the information is undamaged. The information is reassembled in the right order thanks to the sequence number of each information packet. Voila! The web page appears on your pc screen.
The TCP connection can be
the guide to click here kept alive for extra requests from the client. This makes it possible for many pages to be requested within a brief time period without having causing the overhead of opening and closing TCP ports. Either client or server can close the connection at any time.
