HTTP The client makes a TCP-IP connection to the host using the domain name or IP number , and the port number given in the address.
If the port number is not specified, 80 is always assumed for HTTP. The server accepts the connection. The client sends a document request consisting of a line of ASCII characters terminated by a CR LF (carriage return, line feed) pair. A well-behaved server will not require the carriage return character.
web services : XML web services are the program components that allow you to build scalable, loosely coupled, platform independent applications.
XML web services enable disparate applications to exchange messages using protocols like HTTP, XML, XSD, SOAP, WSDL. Web service is a business logic implementation. The client need to know the location of web service and which methods to call.
eg: stock exchange
XML web services directories: These provide a central place to store published information about the web service. UDDI mention the information that can be published for a web service.
Discovery: Using this process, client can locate the document that describes the xml web service. This document is WSDL written.
Xml web services description: The XML web service description is XML document that specifies the format of message that an xml web service understands.
eg: it has soap messages that are used when methods on web services are called.
Wire formats: uses open wire formats. Open wire formats are the rules understood by all systems which support HTTP, soap. Http-get and Http-post are the regular web protocols used for sending request. soap protocol allows to exchange structured and typed information between applications on the internet.
The soap protocol consists of four parts.
The first part is mandatory and defines the envelope that contains the message.
The soap envelope is the basic unit of exchange between the processors of soap messages.
The second part defines the optional data encoding rules that are used to encode application specific data types.
The third type defines the request/response pattern of message exchanges between xml web services
The fourth part which is optional, the binding between soap and http protocols.
How the client can locate the web service
1. The client tries to find an xml web service (request to UDDI and other directory service)
2. A url to discovery document is linked (.disco file)
3. The discovery document is requested by the client
4. The web server returns the discovery document
5. The discovery document contain description of the web service, which is then requested by the client.
6. The service description is returned The client requests the xml web service The service response is returned