Divya's Blog

Posts Tagged ‘Programming


icon for notepad

Sometimes we get irritated if our favorite website is not opened,it may blocked because of some reasons.Here comes solution for these kind of problems.

Follow these steps:

1.open the Notepad

2.Enter the below

@echo off
title web blocked
nslookup

3.Save it as in  batch file format in desktop

e.g block.bat

4.Then click the batch file(block.bat) it will pop up command prompt.

5.There you type website url

e.g http://www.facebook.com

6.After that,command prompt displays some IP address of website you typed.

7.Copy the IP address and enter it into browser tab,then you will be directed to the particular site.

 


		
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SOA is based on four important concepts:-

 

1.Boundaries are well defined

  • In SOA, everything is formalized.
  • The client who is consuming the service does need to know how the implementation of

the service is done.

  • In SOA the rule is if we do enhancement we do not need to change anything at

the client.

  • SOA based application only understands that there is an end point,

contract and bindings.

     

2.Services evolves

  • SOA service versioned and you can host those services in new end points.

For instance we have a service called as “SearchTickets (TicketNumber) “which

gives details based on TicketNumber and its exposed on end point “ep1”.

Tomorrow we want make our SearchTickets service more useful by also providing an

extra    option of  allowing to search by passenger name. Some just declare a

new end point “ep2” with service “SearchTickets (TicketNumber,Passenger Name)”.

So the client who is consuming the service at end point ep1 continues and at the

other end  we have also evolved our service by adding new end points ep2.

3. Services share only schemas and contracts

  • Services use Schemas to represent data and contracts to understand behavior.
  • They’re not use language dependent types or classes in order to understand data

and behavior.

  • XML is used to define schemas and contracts. Due to this there is not heavy coupling

between environments.

4. Service compatibility is policy based

  • Policy describes the capabilities of the system.
  • Depending on policies the services can degrade to match the service for the client.

For instance your service needs to be hosted for two types of client one which uses Remoting as the communication methodology while other client uses DCOM. An ideal SOA service can cater to both of them accordingto there communication policies.


DCOM allows for creating objects distributed across a network, a protocol for invoking that object’s methods, and secures access to the object.

v  DCOM provides a wrapper around COM, hence it is a backwards compatible extension.

v  DCOM uses Remote Procedural Calls (RPC) using Open Software Foundation’s Distributed Computing Environment.

These RPC are implemented over TCP/IP and named pipes. The protocol which is actually being used is registered just prior to use, as opposed to being registered at initialization time. The reason for this is that if a protocol is not being used, it will not be loaded. In order to inform an object that the client is still alive, periodic pinging is used. Hence, when the client has died and no ping has been received (to refresh it) before the expiration time, the server object will perform some clean up tasks (including decrementing its reference count). Since RPC across a network are typically slow (compared to processes residing on the same machine),

  • DCOM sends multiple requests in the same call. For example, in COM, the program performs a QueryInterface, one interface at a time.
  • In DCOM, multiple QueryInterfaces are all clustered into one call. This clustering optimization trick is also used when creating an instance of the object and serializing it with data.
  • These two operations usually occur together, DCOM allows one method which will perform both operations in one call without waiting for an acknowledgment from the first task before performing the second one.

Similarly, when a client pings its server object, it  can do it in one call.

  • Moreover, if there are multiple clients sending pings to multiple servers, an optimization is made where the multiple pings going to the same object are consolidated into just one ping. This is to cut down on the use of precious bandwidth used only for pinging.

The client has the control to set the computer which will be responsible for the lifetime of the object.

Call security is implemented in  four ways:

  1. Authentication (to prevent false clients from impersonating the true client),
  2. Authorization (to insure that a client only does what it is authorized to do),
  3. Data integrity (to insure that data was not tampered with during transit) and
  4. Data privacy (to insure that only designated sources can read it).

ü  The client gives the server various access privileges to access memory or disk space

 

  creation of  DCOM object in VB6

 Using the CreateObject method  we  can create a DCOM object. We  have to put the server name in the registry.


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