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Domain Name Systems, Well known Protocols, Windows Sockets, Basic Sockets Operations, Windows Socket Library, WinSock Initialization, Internet protocols, Server and client system. As you can see in this file, how descriptive above mentioned points are explained in this lecture of computer programming. VU is one of best university for computer science in our country.
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Domain Name System (DNS), the locator service of choice in Microsoft® Windows®, is an industry-standard protocol that locates computers on an IP-based network. IP networks such as the Internet and Windows networks rely on number-based addresses to process information. Users however, are better at remembering letter- based addresses, so it is necessary to translate user-friendly names http://www.vu.edu.pk into addresses that the network can recognize ( 203.215.177.33 ).
Domain Name System, DNS, is an industry-standard protocol used to locate computers on an IP-based network. Users are better at remembering friendly names, such as www.microsoft.com or msdn.microsoft.com, than number-based addresses, such as 207.46.131.137.
IP networks, such as the Internet and Microsoft® Windows® 2000 networks rely on number-based addresses to ferry information throughout the network; therefore, it is necessary to translate user-friendly names (www.microsoft.com) into addresses that
The WSAStartup function initiates use of WS2_32.DLL by a process.
int WSAStartup( WORD wVersionRequested , /MAKEWORD(2,2)/ LPWSADATA** lpWSAData /*POINTER TO THE WSADATA structure );
An application cannot call WSAGetLastError to determine the error code as is normally done in Windows Sockets if WSAStartup fails. The WS2_32.DLL will not have been loaded in the case of a failure so the client data area where the last error information is stored could not be established.
The WSAStartup function must be the first Windows Sockets function called by an application or DLL. It allows an application or DLL to specify the version of Windows Sockets required and retrieve details of the specific Windows Sockets implementation. The application or DLL can only issue further Windows Sockets functions after successfully calling WSAStartup.
In order to support future Windows Sockets implementations and applications that can have functionality differences from the current version of Windows Sockets, a negotiation takes place in WSAStartup. The caller of WSAStartup and the WS2_32.DLL indicate to each other the highest version that they can support, and each confirms that the other's highest version is acceptable. Upon entry to WSAStartup , the WS2_32.DLL examines the version requested by the application. If this version is equal to or higher than the lowest version supported by the DLL, the call succeeds and the DLL returns in wHighVersion the highest version it supports and in wVersion the minimum of its high version and wVersionRequested. The WS2_32.DLL then assumes that the application will use wVersion If the wVersion parameter of the WSADATA structure is unacceptable to the caller, it should call WSACleanup and either search for another WS2_32.DLL or fail to initialize.
It is legal and possible for an application written to this version of the specification to successfully negotiate a higher version number version. In that case, the application is only guaranteed access to higher-version functionality that fits within the syntax defined in this version, such as new Ioctl codes and new behavior of existing functions. New functions may be inaccessible. To get full access to the new syntax of a future version, the application must fully conform to that future version, such as compiling against a new header file, linking to a new library, or other special cases.
This negotiation allows both a WS2_32.DLL and a Windows Sockets application to support a range of Windows Sockets versions. An application can use WS2_32.DLL if there is any overlap in the version ranges. The following table shows how WSAStartup works with different applications and WS2_32.DLL versions.
