A web service is a program that calls a method which is on another computer on the network.
A ' Web service' (also Web Service ) is defined by the W3C as "a software system designed to support interoperable Machine to Machine interaction over a network "  . Web services are frequently just Web APIs that can be accessed over a network, such as the Internet , and executed on a remote system hosting the requested services.
(Wikipedia, accessed July 2008, http://en.wikipedia.org/wiki/Web_service)
The current layer systems is called the Internet Protocol Stack.
Each layer has a set of protocols that set the rules for how each layer behaves.
The protocols are to break the information down into datagrams or packets so they can travel over the network to their destination. Then the same protocols are used at the destination to put the datagrams / packets back to their original format.
network: routing of datagrams from source to destination
IP, routing protocols
link: data transfer between neighboring network elements
application transport network link
Encapsulation message segment datagram frame source application transport network link destination application transport network link router switch H t H n H l M H t H n M H t M M H t H n H l M H t H n M H t M M network link link H t H n H l M H t H n M H t H n H l M H t H n M H t H n H l M H t H n H l M
Active Server Pages (ASP) is a technology that allows for the generation of HTML pages that are responding to a set of instructions (dynamic) prior to being delivered to the browser.
ASP is not a language
ASP is browser independent
Other technologies are;
But What Makes an Active Server Page Work ? Clients system Server Asp.dll Pre processing Translation to HTML Scripting Agents Execution Request HTML for display 1. Prestored instructions written by author
Server User 2. Client requests web page With the use of the web browser. 3. Server locates files 4. Html and graphics returned to user and are displayed in the browser. 1. Author writes html and graphics
Multiple objects can be sent over single TCP connection between client and server.
HTTP/1.1 uses persistent connections in default mode
GET, POST, HEAD, same as HTTP 1.0
An Example of Nonpersistent HTTP Suppose user enters URL www.someSchool.edu/someDepartment/home.index This URL contains text and references to 10 jpeg images. Therefore there is 11 objects that must be sent to the user. An example of the steps that are taken are on the next 2 slides.
1a . HTTP client initiates TCP connection to HTTP server (process) at www.someSchool.edu on port 80 2. HTTP client sends HTTP request message (containing URL) into TCP connection socket. Message indicates that client wants object someDepartment/home.index 3. HTTP server receives request message, forms response message containing requested object, and sends message into its socket time 1b. HTTP server at host www.someSchool.edu waiting for TCP connection at port 80. “accepts” connection, notifying client
Nonpersistent HTTP (cont.) 4 . HTTP client receives response message containing html file, displays html. Parsing html file, finds 10 referenced jpeg objects 6. Steps 1-5 repeated for each of 10 jpeg objects 5. HTTP server closes TCP connection. time
If the method is post, then the body contains any data that is being sent to the server. Eg: data from a form.
If the method is GET then the body is empty
Contains for a Response:
If the request is successful, then the body contains the HTML code & script, ready for the browser’s interpretation
HTTP Request Request: GET/default.asp /HTTP://www.Wrox.com /HTTP1.1 Header: ACCEPT:*/* ACCEPT_LANGUAGE: en-us CONNECTION:Keep-Alive HOST:webdev.wrox.co.uk REFERER:http://webdev.wrox.co.uk/books/SampleList.asp?bookcode=3382 USER_AGENT:Mozilla/4.0 (compatible;MSIE 5.01;Windows NT 5.0) Body;(empty) Request line Header Body GET message Client form data
A SOAP envelope can contain any XML data, just as an HTTP envelope can contain any data in its entity-body.
In every existing SOAP envelope contains a description of an RPC call in a format similar to that of XML-RPC.
Message Service Specification (MSS) The MSS contains two parts: Header container . This is the first MIME part, containing One SOAP message. The SOAP message is an XML document consisting of a SOAP Envelope element. The SOAP Envelope element consists of: SOAP-ENV:Header. This is a generic mechanism for adding features to SOAP message, including ebXML specific header elements. SOAP-ENV:Body. This is a container for message service handler control data and information related to the payload parts of the message. Payload containers. There can be zero or more additional MIME parts containing application specific payloads.
Because of the verbose XML format, SOAP can be considerably slower than competing middleware technologies such as CORBA . This may not be an issue when only small messages are sent.
On the other side, SOAP has Message Transmission Optimization Mechanism .
When relying on HTTP as a transport protocol and not using WS-Addressing or an ESB , the roles of the interacting parties are fixed. Only one party (the client) can use the services of the other. So developers must use polling instead of notification in these common cases.