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winsock2.h header

This header is used by multiple technologies. For more information, see:

winsock2.h contains the following programming interfaces:

Functions

 
__WSAFDIsSet

The __WSAFDIsSet function (winsock2.h) specifies whether a socket is included in a set of socket descriptors.
accept

The accept function permits an incoming connection attempt on a socket.
bind

The bind function associates a local address with a socket. (bind function (winsock2.h))
closesocket

The closesocket function closes an existing socket. (closesocket function (winsock2.h))
connect

The connect function establishes a connection to a specified socket.
FD_SET

The FD_SET macro (winsock2.h) is used by Windows Sockets (Winsock) functions and service providers to place sockets into a set.
gethostbyaddr

The gethostbyaddr function retrieves the host information corresponding to a network address. (gethostbyaddr is no longer recommended, use getnameinfo instead)
gethostbyname

The gethostbyname function (winsock2.h) function retrieves host information corresponding to a host name from a host database.
gethostname

The gethostname function (winsock2.h) retrieves the standard host name for the local computer.
GetHostNameW

The GetHostNameW function retrieves the standard host name for the local computer as a Unicode string.
getpeername

The getpeername function (winsock2.h) retrieves the address of the peer to which a socket is connected.
getprotobyname

The getprotobyname function (winsock2.h) retrieves the protocol information corresponding to a protocol name.
getprotobynumber

The getprotobynumber function (winsock2.h) retrieves protocol information corresponding to a protocol number.
getservbyname

The getservbyname function (winsock2.h) retrieves service information corresponding to a service name and protocol.
getservbyport

The getservbyport function (winsock2.h) retrieves service information corresponding to a port and protocol.
getsockname

The getsockname function (winsock2.h) retrieves the local name for the specified socket descriptor.
getsockopt

The getsockopt function retrieves the current value for a socket option associated with a socket of any type, in any state, and stores the result in optval.
htond

Converts a double from host to TCP/IP network byte order (which is big-endian).
htonf

Converts a float from host to TCP/IP network byte order (which is big-endian).
htonl

The htonl function (winsock2.h) converts a u_long from host to TCP/IP network byte order, which is big-endian.
htonll

Converts an unsigned __int64 from host to TCP/IP network byte order (which is big-endian).
htons

The htons function (winsock2.h) converts a u_short from host to TCP/IP network byte order, which is big-endian.
inet_addr

The inet_addr function (winsock2.h) converts a string containing an IPv4 dotted-decimal address into a proper address for the IN_ADDR structure.
inet_ntoa

The inet_ntoa function (winsock2.h) converts an (Ipv4) Internet network address into an ASCII string in Internet standard dotted-decimal format.
ioctlsocket

The ioctlsocket function (winsock2.h) controls the I/O mode of a socket and can be used on any socket in any state.
listen

The listen function places a socket in a state in which it is listening for an incoming connection.
ntohd

Converts an unsigned __int64 from TCP/IP network order to host byte order (which is little-endian on Intel processors) and returns a double.
ntohf

Converts an unsigned __int32 from TCP/IP network order to host byte order (which is little-endian on Intel processors) and returns a float.
ntohl

The ntohl function (winsock2.h) converts a u_long from TCP/IP network order to host byte order (which is little-endian on Intel processors).
ntohll

Converts an unsigned __int64 from TCP/IP network order to host byte order (which is little-endian on Intel processors).
ntohs

The ntohs function (winsock2.h) converts a u_short from TCP/IP network byte order to host byte order (which is little-endian on Intel processors).
ProcessSocketNotifications

Associates a set of sockets with a completion port, and retrieves any notifications that are already pending on that port. Once associated, the completion port receives the socket state notifications that were specified.
recv

The recv function (winsock2.h) receives data from a connected socket or a bound connectionless socket.
recvfrom

The recvfrom function receives a datagram, and stores the source address.
select

The select function determines the status of one or more sockets, waiting if necessary, to perform synchronous I/O.
send

Sends data on a connected socket. (send)
sendto

The sendto function (winsock2.h) is used to write outgoing data on a socket.
setsockopt

The setsockopt function (winsock2.h) sets the current value for a socket option associated with a socket of any type, in any state.
shutdown

The shutdown function (winsock2.h) is used on all types of sockets to disable reception, transmission, or both.
socket

The socket function creates a socket that is bound to a specific transport service provider.
SocketNotificationRetrieveEvents

This inline helper function is provided as a convenience to retrieve the events mask from an OVERLAPPED_ENTRY.
WSAAccept

The WSAAccept function conditionally accepts a connection based on the return value of a condition function, provides quality of service flow specifications, and allows the transfer of connection data.
WSAAddressToStringA

Converts all components of a sockaddr structure into a human-readable string representation of the address. (ANSI)
WSAAddressToStringW

Converts all components of a sockaddr structure into a human-readable string representation of the address. (Unicode)
WSAAsyncGetHostByAddr

The WSAAsyncGetHostByAddr function (winsock2.h) asynchronously retrieves host information that corresponds to an address.
WSAAsyncGetHostByName

The WSAAsyncGetHostByName function (winsock2.h) asynchronously retrieves host information that corresponds to a host name.
WSAAsyncGetProtoByName

The WSAAsyncGetProtoByName function (winsock2.h) asynchronously retrieves protocol information that corresponds to a protocol name.
WSAAsyncGetProtoByNumber

The WSAAsyncGetProtoByNumber function (winsock2.h) asynchronously retrieves protocol information that corresponds to a protocol number.
WSAAsyncGetServByName

The WSAAsyncGetServByName function (winsock2.h) asynchronously retrieves service information that corresponds to a service name and port.
WSAAsyncGetServByPort

The WSAAsyncGetServByPort function (winsock2.h) asynchronously retrieves service information that corresponds to a port and protocol.
WSAAsyncSelect

The WSAAsyncSelect function (winsock2.h) requests Windows message based notification of network events for a socket.
WSACancelAsyncRequest

The WSACancelAsyncRequest function (winsock2.h) cancels an incomplete asynchronous operation.
WSACancelBlockingCall

The WSACancelBlockingCall function has been removed in compliance with the Windows Sockets 2 specification, revision 2.2.0.
WSACleanup

The WSACleanup function (winsock2.h) terminates use of the WS2_32.dll.
WSACloseEvent

The WSACloseEvent function closes an open event object handle.
WSAConnect

The WSAConnect function establishes a connection to another socket application, exchanges connect data, and specifies required quality of service based on the specified FLOWSPEC structure.
WSAConnectByList

Establishes a connection to one out of a collection of possible endpoints represented by a set of destination addresses (host names and ports).
WSAConnectByNameA

Establishes a connection to a specified host and port. (ANSI)
WSAConnectByNameW

Establishes a connection to a specified host and port. (Unicode)
WSACreateEvent

The WSACreateEvent function creates a new event object.
WSADuplicateSocketA

The WSADuplicateSocket function returns a WSAPROTOCOL_INFO structure that can be used to create a new socket descriptor for a shared socket. The WSADuplicateSocket function cannot be used on a QOS-enabled socket. (ANSI)
WSADuplicateSocketW

The WSADuplicateSocket function returns a WSAPROTOCOL_INFO structure that can be used to create a new socket descriptor for a shared socket. The WSADuplicateSocket function cannot be used on a QOS-enabled socket. (Unicode)
WSAEnumNameSpaceProvidersA

The WSAEnumNameSpaceProviders function retrieves information on available namespace providers. (ANSI)
WSAEnumNameSpaceProvidersExA

Retrieves information on available namespace providers. (ANSI)
WSAEnumNameSpaceProvidersExW

Retrieves information on available namespace providers. (Unicode)
WSAEnumNameSpaceProvidersW

The WSAEnumNameSpaceProviders function retrieves information on available namespace providers. (Unicode)
WSAEnumNetworkEvents

The WSAEnumNetworkEvents function discovers occurrences of network events for the indicated socket, clear internal network event records, and reset event objects (optional).
WSAEnumProtocolsA

The WSAEnumProtocols function retrieves information about available transport protocols. (ANSI)
WSAEnumProtocolsW

The WSAEnumProtocols function retrieves information about available transport protocols. (Unicode)
WSAEventSelect

The WSAEventSelect function specifies an event object to be associated with the specified set of FD_XXX network events.
WSAGetLastError

The WSAGetLastError function (winsock2.h) returns the error status for the last Windows Sockets operation that failed.
WSAGetOverlappedResult

The WSAGetOverlappedResult function retrieves the results of an overlapped operation on the specified socket.
WSAGetQOSByName

The WSAGetQOSByName function initializes a QOS structure based on a named template, or it supplies a buffer to retrieve an enumeration of the available template names.
WSAGetServiceClassInfoA

The WSAGetServiceClassInfo function retrieves the class information (schema) pertaining to a specified service class from a specified namespace provider. (ANSI)
WSAGetServiceClassInfoW

The WSAGetServiceClassInfo function retrieves the class information (schema) pertaining to a specified service class from a specified namespace provider. (Unicode)
WSAGetServiceClassNameByClassIdA

The WSAGetServiceClassNameByClassId function retrieves the name of the service associated with the specified type. This name is the generic service name, like FTP or SNA, and not the name of a specific instance of that service. (ANSI)
WSAGetServiceClassNameByClassIdW

The WSAGetServiceClassNameByClassId function retrieves the name of the service associated with the specified type. This name is the generic service name, like FTP or SNA, and not the name of a specific instance of that service. (Unicode)
WSAHtonl

The WSAHtonl function converts a u_long from host byte order to network byte order.
WSAHtons

The WSAHtons function converts a u_short from host byte order to network byte order.
WSAInstallServiceClassA

The WSAInstallServiceClass function registers a service class schema within a namespace. (ANSI)
WSAInstallServiceClassW

The WSAInstallServiceClass function registers a service class schema within a namespace. (Unicode)
WSAIoctl

The WSAIoctl function controls the mode of a socket.
WSAIsBlocking

This function has been removed in compliance with the Windows Sockets 2 specification, revision 2.2.0. (WSAIsBlocking)
WSAJoinLeaf

The WSAJoinLeaf function joins a leaf node into a multipoint session, exchanges connect data, and specifies needed quality of service based on the specified FLOWSPEC structures.
WSALookupServiceBeginA

The WSALookupServiceBegin function initiates a client query that is constrained by the information contained within a WSAQUERYSET structure. (ANSI)
WSALookupServiceBeginW

The WSALookupServiceBegin function initiates a client query that is constrained by the information contained within a WSAQUERYSET structure. (Unicode)
WSALookupServiceEnd

The WSALookupServiceEnd function is called to free the handle after previous calls to WSALookupServiceBegin and WSALookupServiceNext.
WSALookupServiceNextA

The WSALookupServiceNext function is called after obtaining a handle from a previous call to WSALookupServiceBegin in order to retrieve the requested service information. (ANSI)
WSALookupServiceNextW

The WSALookupServiceNext function is called after obtaining a handle from a previous call to WSALookupServiceBegin in order to retrieve the requested service information. (Unicode)
WSANSPIoctl

Enables developers to make I/O control calls to a registered namespace.
WSANtohl

The WSANtohl function converts a u_long from network byte order to host byte order.
WSANtohs

The WSANtohs function converts a u_short from network byte order to host byte order.
WSAPoll

The WSAPoll function determines status of one or more sockets.
WSAProviderConfigChange

The WSAProviderConfigChange function notifies the application when the provider configuration is changed.
WSARecv

Receives data from a connected socket or a bound connectionless socket. (WSARecv)
WSARecvDisconnect

The WSARecvDisconnect function terminates reception on a socket, and retrieves the disconnect data if the socket is connection oriented.
WSARecvFrom

Receives a datagram and stores the source address.
WSARemoveServiceClass

The WSARemoveServiceClass function permanently removes the service class schema from the registry.
WSAResetEvent

The WSAResetEvent function resets the state of the specified event object to nonsignaled.
WSASend

Sends data on a connected socket. (WSASend)
WSASendDisconnect

The WSASendDisconnect function initiates termination of the connection for the socket and sends disconnect data.
WSASendMsg

Sends data and optional control information from connected and unconnected sockets. Note  This function is a Microsoft-specific extension to the Windows Sockets specification. .
WSASendTo

Sends data to a specific destination, using overlapped I/O where applicable.
WSASetBlockingHook

This function has been removed in compliance with the Windows Sockets 2 specification, revision 2.2.0. (WSASetBlockingHook)
WSASetEvent

The WSASetEvent function sets the state of the specified event object to signaled.
WSASetLastError

The WSASetLastError function (winsock2.h) sets the error code that can be retrieved through the WSAGetLastError function.
WSASetServiceA

The WSASetService function registers or removes from the registry a service instance within one or more namespaces. (ANSI)
WSASetServiceW

The WSASetService function registers or removes from the registry a service instance within one or more namespaces. (Unicode)
WSASocketA

The WSASocket function creates a socket that is bound to a specific transport-service provider. (ANSI)
WSASocketW

The WSASocket function creates a socket that is bound to a specific transport-service provider. (Unicode)
WSAStartup

The WSAStartup function (winsock2.h) initiates use of the Winsock DLL by a process.
WSAStringToAddressA

The WSAStringToAddress function converts a network address in its standard text presentation form into its numeric binary form in a sockaddr structure, suitable for passing to Windows Sockets routines that take such a structure. (ANSI)
WSAStringToAddressW

The WSAStringToAddress function converts a network address in its standard text presentation form into its numeric binary form in a sockaddr structure, suitable for passing to Windows Sockets routines that take such a structure. (Unicode)
WSAUnhookBlockingHook

This function has been removed in compliance with the Windows Sockets 2 specification, revision 2.2.0. (WSAUnhookBlockingHook)
WSAWaitForMultipleEvents

Returns when one or all of the specified event objects are in the signaled state, when the time-out interval expires, or when an I/O completion routine has executed.

Callback functions

 
LPWSAOVERLAPPED_COMPLETION_ROUTINE

TBD (LPWSAOVERLAPPED_COMPLETION_ROUTINE)

Structures

 
AFPROTOCOLS

The AFPROTOCOLS structure supplies a list of protocols to which application programmers can constrain queries. The AFPROTOCOLS structure is used for query purposes only.
BLOB

The BLOB structure (winsock2.h), derived from Binary Large Object, contains information about a block of data.
fd_set

The Fd_set structure (winsock2.h) is used by Windows Sockets (Winsock) functions and service providers to place sockets into a set.
HOSTENT

The HOSTENT structure (winsock2.h) is used by functions to store information about a given host, such as host name, IPv4 address, and so forth.
in_addr

The in_addr structure represents an IPv4 Internet address.
LINGER

The LINGER structure (winsock2.h) maintains information about a specific socket that specifies how that socket should behave when data is queued.
PROTOENT

The PROTOENT structure (winsock2.h) contains the name and protocol numbers that correspond to a given protocol name.
QOS

The QOS structure provides the means by which QOS-enabled applications can specify quality of service parameters for sent and received traffic on a particular flow.
SERVENT

The SERVENT structure (winsock2.h) is used to store or return the name and service number for a given service name.
SOCK_NOTIFY_REGISTRATION

Represents info supplied to the ProcessSocketNotifications function.
TIMEVAL

The TIMEVAL structure (winsock2.h) is used to specify a time interval. It is associated with the Berkeley Software Distribution (BSD) Time.h header file.
WSACOMPLETION

Specifies completion notification settings for I/O control calls made to a registered namespace.
WSADATA

The WSADATA structure (winsock2.h) contains information about the Windows Sockets implementation.
WSANAMESPACE_INFOA

Contains all registration information for a namespace provider. (WSANAMESPACE_INFOA)
WSANAMESPACE_INFOEXA

Contains all registration information for a namespace provider. (WSANAMESPACE_INFOEXA)
WSANAMESPACE_INFOEXW

Contains all registration information for a namespace provider. (WSANAMESPACE_INFOEXW)
WSANAMESPACE_INFOW

Contains all registration information for a namespace provider. (WSANAMESPACE_INFOW)
WSANETWORKEVENTS

The WSANETWORKEVENTS structure is used to store a socket's internal information about network events.
WSANSCLASSINFOA

The WSANSCLASSINFO structure provides individual parameter information for a specific Windows Sockets namespace. (ANSI)
WSANSCLASSINFOW

The WSANSCLASSINFO structure provides individual parameter information for a specific Windows Sockets namespace. (Unicode)
WSAOVERLAPPED

Provides a communication medium between the initiation of an overlapped I/O operation and its subsequent completion.
WSAPOLLFD

Stores socket information used by the WSAPoll function.
WSAPROTOCOL_INFOA

Used to store or retrieve complete information for a given protocol. (ANSI)
WSAPROTOCOL_INFOW

Used to store or retrieve complete information for a given protocol. (Unicode)
WSAPROTOCOLCHAIN

The WSAPROTOCOLCHAIN structure contains a counted list of Catalog Entry identifiers that comprise a protocol chain.
WSAQUERYSET2A

Provides relevant information about a given service, including service class ID, service name , applicable namespace identifier and protocol information, as well as a set of transport addresses at which the service listens. (ANSI)
WSAQUERYSET2W

Provides relevant information about a given service, including service class ID, service name , applicable namespace identifier and protocol information, as well as a set of transport addresses at which the service listens. (Unicode)
WSAQUERYSETA

Provides relevant information about a given service, including service class ID, service name, applicable namespace identifier and protocol information, as well as a set of transport addresses at which the service listens. (ANSI)
WSAQUERYSETW

Provides relevant information about a given service, including service class ID, service name, applicable namespace identifier and protocol information, as well as a set of transport addresses at which the service listens. (Unicode)
WSASERVICECLASSINFOA

The WSASERVICECLASSINFO structure contains information about a specified service class. For each service class in Windows Sockets 2, there is a single WSASERVICECLASSINFO structure. (ANSI)
WSASERVICECLASSINFOW

The WSASERVICECLASSINFO structure contains information about a specified service class. For each service class in Windows Sockets 2, there is a single WSASERVICECLASSINFO structure. (Unicode)
WSAVERSION

The WSAVERSION structure provides version comparison in Windows Sockets.

Enumerations

 
WSAECOMPARATOR

The Windows Sockets WSAECOMPARATOR enumeration type is used for version-comparison semantics in Windows Sockets 2.