fd_set structure (winsock2.h)

The fd_set structure is used by various Windows Sockets functions and service providers, such as the select function, to place sockets into a "set" for various purposes, such as testing a given socket for readability using the readfds parameter of the select function.

Syntax

typedef struct fd_set {
  u_int  fd_count;
  SOCKET fd_array[FD_SETSIZE];
} fd_set, FD_SET, *PFD_SET, *LPFD_SET;

Members

fd_count

The number of sockets in the set.

fd_array[FD_SETSIZE]

An array of sockets that are in the set. The variable FD_SETSIZE defaults to 64.

Remarks

Be careful not to confuse the FD_SET typedef of the fd_set structure with the FD_SET macro. That said, the FD_SET macro and the fd_set structure are related, and often used in conjunction.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Header	winsock2.h (include Winsock2.h, Winsock.h)

See also

WSAAsyncSelect

WSAEventSelect

select