Some concepts
What`s the content of web?
The web consists of gazillions of clients(using browsers like Mozilla or IE ) and servers (using web server apps like Apache) connected through wires and wireless networks.
What does your web server do ?
A web server takes a client request and gives something back to the client.
A web browser lets a user requenst a resource .The web server gets teh request, finds the resource, and returns something to the user .When we say "server" ,we mean either the physical machine (hardware) or the web server application(software).
What does a web client do?
A web client lets the user request something on the server, and shows the user the result of the request.
The browser is the piece of software(like Netscape or Mozilla) that knows how to communicate with the server.The browser`s other big job is interpreting the HTML code and rendering the web page for the user.
What does HTML do?
The HTML (HyperText Markup Language) tells the browser how to present the content to the user.All weh browser know what to do with HTML,although sometimes an older browser might not understand parts if a page that was written using newer versions of HTML.
What does HTTP do?
HTTP is the protocol clients and servers use on the web to communicate. HTTP allows for simle request and response conversations.The client sends an Http request ,and the server answers with an HTTP response:If you are a web server,you speak HTTP.
The server uses HTTP to send HTML to the client.
Get and Post:
Get is the simplest HTTP method ,and its main job in life is to ask the server to get a resource and send it back. Thatresource might be an HTML page,a JPG,a PDF,etc.Doesn`t matter.The point of Get is to get something back from the server.
Post is a more powerful request. It is like a Get plus plus.With POST,you can request something and at the same time send form data to the server.
URL :
Uniform Resource Locations.Every resourse on the web has its own unique address, in the URL format. Lets see a URL :
Protocol: Tells the server which communications protocol (in this case HTTP) will be used.
Server: The unique name of the phisical sever you are looking for. This name maps to a unique IP address. IP address are numeric and take the form of "xxx.yyy.zzz.aaa" . You can specify an IP address here instead of a server name ,but a server name is a lot easier to remember.
Port: This part of the URL is optional. A single server supports many ports. A server application is identified by a port. If you do not specify a port in your URL, then port 80 is the default,and as luck would have it , that is the default port for web servers.
Path: The path to the location, on the server,of the resource being requested.Because most of the early severs on the web ran Unix ,Unix syntax is still used to describe the directory hierarches on the web server.
Resource: The name of the content being requested. This could be an HTML page,a sevlet ,an image,PDF, music video, or anything else the server feels like severing. If this optional part of the URL is left out, most web severs will look for index.html by default.
not show-Optional Query String: If this was a GET request,the extra info would be appended to the end of this URL,starting with a question mark"?" ,and with each parameter seperated by an anpersand "&".
