(zz)WSAEWOULDBLOCK 與 FD_WRITE 說明

WinSock Tips

1. WSAEWOULDBLOCK 錯誤說明

在非鎖定套接字上

函式名	說明
WSAAccept, accept	應用程式沒有收到連線請求，再次呼叫，便可檢查連線情況
closesocket	大多數情況下，這個錯誤意味著已隨SO_LINGER選項一道呼叫了 setsockopt，而且已設定了一個非零的超時值
WSAConnect, connect	應用程式已初始化，再次呼叫，便可檢查是否完成
WSARecv,recv WSARecvFrom, recvfrom	沒有收到資料，銷後再次檢查
WSASend, send WSASendTo, sendto	外出資料無緩衝區可用，銷後再試

2. FD_WRITE 觸發條件

只有在三種條件下，才會發出 FD_WRITE 通知
. connect, WSAConnect ，一個套接字首次建立了連線
. accept, WSAAccept, 套接字被接受以後
. send, WSASend, sendto, WSASendTo操作失敗，返回了 WSAEWOULDBLOCK 錯誤，而且緩衝
再次變得可用時

[@more@]If no incoming data is available at the socket, the recv call blocks and waits for data to arrive according to the blocking rules defined for WSARecv with the MSG_PARTIAL flag not set unless the socket is nonblocking. In this case, a value of SOCKET_ERROR is returned with the error code set to WSAEWOULDBLOCK. The select, WSAAsyncSelect, or WSAEventSelect functions can be used to determine when more data arrives.