Windows* Sockets 2 Application Programming Interface An Interface for Transparent Network Programming Under Microsoft Windowstm revision 2 August 7, 1997
Extended Byte Order Conversion Routines
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- 38 Support for Scatter/Gather I/O
- 39 Protocol-Independent Multicast and Multipoint
- 40 Summary of New Socket Options
- 41 Summary of New Socket Ioctl Opcodes
37 Extended Byte Order Conversion RoutinesWinSock 2 does not assume that the network byte order for all protocols is the same. Therefore a set of conversion routines are supplied for converting 16 and 32 bit quantities to and from network byte order. These routines take as an input parameter the socket handle, which has a WSAPROTOCOL_INFO structure associated with it. The NetworkByteOrder field in the WSAPROTOCOL_INFO structure specifies what the desired network byte order is (currently either “big-endian” or “little-endian”).. 38 Support for Scatter/Gather I/OThe WSASend(), WSASendTo(), WSARecv(), and WSARecvFrom() routines all take an array of application buffers as input parameters and thus may be used for scatter/gather (or vectored) I/O. This can be very useful in instances where portions of each message being transmitted consist of one or more fixed length “header” components in addition to message body. Such header components need not be concatenated by the application into a single contiguous buffer prior to sending. Likewise on receiving, the header components can be automatically split off into separate buffers, leaving the message body “pure”. When receiving into multiple buffers, completion occurs as data arrives from the network, regardless of whether all of the supplied buffers are utilized. 39 Protocol-Independent Multicast and MultipointJust as WinSock 2 allows the basic data transport capabilities of numerous transport protocols to be accessed in a generic manner, it also provides a generic way to utilize multipoint and multicast capabilities of transports that implement these features. To simplify, the term multipoint is used hereafter to refer to both multicast and multipoint communications. Current multipoint implementations (e.g. IP multicast, ST-II, T.120, ATM UNI, etc.) vary widely with respect to how nodes join a multipoint session, whether a particular node is designated as a central or root node, and whether data is exchanged between all nodes or only between a root node and the various leaf nodes. WinSock 2’s WSAPROTOCOL_INFO struct is used to declare the various multipoint attributes of a protocol. By examining these attributes the programmer will know what conventions to follow with the applicable WinSock 2 functions to setup, utilize and teardown multipoint sessions. The features of WinSock 2 that support multicast can be summarized as follows:
Note that the inclusion of these multipoint features in WinSock 2 does not preclude an application from using an existing protocol-dependent interface, such as the Deering socket options for IP multicast (as described in the TCP/IP section of the Windows Sockets 2 Protocol-Specific Annex). Please refer to Appendix B. Multipoint and Multicast Semantics for detailed information on how the various multipoint schemes are characterized and how the applicable features of WinSock 2 are utilized. 40 Summary of New Socket OptionsThe new socket options for Winsock 2 are summarized in the following table. More detailed information is provided in section 3 under getsockopt() and/or setsockopt(). There are other new protocol-specific socket options which can be found in the protocol-specific annex.
41 Summary of New Socket Ioctl OpcodesThe new socket ioctl opcodes for Winsock 2 are summarized in the following table. More detailed information is provided in section 3 under WSAIoctl(). Note that WSAIoctl() also supports all the ioctl opcodes specified in ioctlsocket(). There are other new protocol-specific ioctl opcodes which can be found in the protocol-specific annex.
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