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

The following table shows the possible error codes.

To accept connections, a socket is first created with WSPSocketbound to a local address with WSPBind, a backlog for incoming connections is specified with WSPListen, and then the connections are accepted with WSPAccept. WSPListenapplies only to sockets that are connection oriented (for example, SOCK_STREAM). The socket sis 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.

This function 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 WSPListenor WSPAcceptwill refill the queue to the current or most recent backlog, if possible, and resume listening for incoming connections.

A Windows Sockets SPI client can call this function 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 backlogvalue, the excess pending connections will be reset and dropped.