WSPListen

The WSPListen function establishes a socket to listen for incoming connections.

int WSPListen (
  SOCKET s,      
  int backlog,   
  LPINT lpErrno  
);

Parameters

s: [in] A descriptor identifying a bound, unconnected socket.
backlog: [in] The maximum length to which the queue of pending connections can grow. If this value is SOMAXCONN, then the service provider should set the backlog to a maximum "reasonable" value. There is no standard provision to find out the actual backlog value.
lpErrno: [out] A pointer to the error code.

Remarks

To accept connections, a socket is first created with WSPSocket bound to a local address with WSPBind, a backlog for incoming connections is specified with WSPListen, and then the connections are accepted with WSPAccept. WSPListen applies only to sockets that are connection oriented (for example, SOCK_STREAM). The socket s is put into "passive'' mode where incoming connection requests are acknowledged and queued pending acceptance by the Windows Sockets SPI client.

This function is typically used by servers that could have more than one connection request at a time: if a connection request arrives with the queue full, the client will receive an error with an indication of WSAECONNREFUSED.

WSPListen should continue to function rationally when there are no available descriptors. It should accept connections until the queue is emptied. If descriptors become available, a later call to WSPListen or WSPAccept will re-fill the queue to the current or most recent "backlog'', if possible, and resume listening for incoming connections.

A Windows Sockets SPI client can call WSPListen more than once on the same socket. This has the effect of updating the current backlog for the listening socket. Should there be more pending connections than the new backlog value, the excess pending connections will be reset and dropped.

Compatibility

backlog is limited (silently) to a reasonable value as determined by the service provider. Illegal values are replaced by the nearest legal value. There is no standard provision to find out the actual backlog value.

Return Values

If no error occurs, WSPListen returns zero. Otherwise, a value of SOCKET_ERROR is returned, and a specific error code is available in lpErrno.

Error Codes

WSAENETDOWN	The network subsystem has failed.
WSAEADDRINUSE	The socket's local address is already in use and the socket was not marked to allow address reuse with SO_REUSEADDR. This error usually occurs at the time of bind, but could be delayed until this function if the bind was to a partially wild-card address (involving ADDR_ANY) and if a specific address needs to be "committed" at the time of this function.
WSAEINPROGRESS	The function is invoked when a callback is in progress.
WSAEINVAL	The socket has not been bound with WSPBind.
WSAEISCONN	The socket is already connected.
WSAEMFILE	No more socket descriptors are available.
WSAENOBUFS	No buffer space is available.
WSAENOTSOCK	The descriptor is not a socket.
WSAEOPNOTSUPP	The referenced socket is not of a type that supports the WSPListen operation.

QuickInfo

  Windows NT: Yes
  Windows: Yes
  Windows CE: Unsupported.
  Header: Declared in ws2spi.h.