//**********************************************************************************
//说明: 阻塞线程下为什么不触发OnRead和OnWrite事件
//作者: licwing 时间: 2001-5-18
//Email: rurality@21cn.com
//**********************************************************************************
1.首先先分析TServerSocket的继承关系
TAbstractSocket->TCustomSocket->TCustomServerSocket->TServerSocket
属性 ServerType 是在 TCustomServerSocket 里面定义的
property ServerType: TServerType read GetServerType write SetServerType;
同时在TCustomServerSocket里定义了TServerWinSocket,用来处理客户连接
TServerWinSocket的继承关系如下:
TCustomWinSocket->TServerWinSocket
也就是说我们在TServerSocket里面触发的OnRead,OnWrite事件事实上是由TServerSocket
的父类TCustomServerSocket中的TServerWinSocket触发的。
2.现在我们分析在TCustomServerSocket里定义的TServerWinSocket客户连接方法
procedure TServerWinSocket.Accept(Socket: TSocket);
var
ClientSocket: TServerClientWinSocket;
ClientWinSocket: TSocket;
Addr: TSockAddrIn;
Len: Integer;
OldOpenType, NewOpenType: Integer;
begin
Len := SizeOf(OldOpenType);
if getsockopt(INVALID_SOCKET, SOL_SOCKET, SO_OPENTYPE, PChar(@OldOpenType),
Len) = 0 then
//从这里开始是处理多线程的
try
if FServerType = stThreadBlocking then
begin
// SO_SYNCHRONOUS_NONALERT = $20 在winsock单元里面定义
//{$EXTERNALSYM SO_SYNCHRONOUS_NONALERT}
NewOpenType := SO_SYNCHRONOUS_NONALERT;
setsockopt(INVALID_SOCKET, SOL_SOCKET, SO_OPENTYPE, PChar(@NewOpenType), Len);
end;
Len := SizeOf(Addr);
ClientWinSocket := WinSock.accept(Socket, @Addr, @Len);
if ClientWinSocket <> INVALID_SOCKET then
begin
ClientSocket := GetClientSocket(ClientWinSocket);
if Assigned(FOnSocketEvent) then
FOnSocketEvent(Self, ClientSocket, seAccept);
if FServerType = stThreadBlocking then
begin
//********多线程事件响应关键部分*******
//TAsyncStyle = (asRead, asWrite, asOOB, asAccept, asConnect, asClose);
//asRead The socket receives notification that the connection is ready for reading.
//asWrite The socket receives notification that the connection is ready for writing.
ClientSocket.ASyncStyles := [];
//*************************************
GetServerThread(ClientSocket);
end;
end;
finally
Len := SizeOf(OldOpenType);
setsockopt(INVALID_SOCKET, SOL_SOCKET, SO_OPENTYPE, PChar(@OldOpenType), Len);
end;
end;
3.ASyncStyles属性只有在TCustomWinSocke类里面定义的，再看SetAsyncStyles过程
procedure TCustomWinSocket.DoSetAsyncStyles;
var
Msg: Integer;
Wnd: HWnd;
Blocking: Longint;
begin
Msg := 0;
Wnd := 0;
if FAsyncStyles <> [] then //非阻塞模式
begin
Msg := CM_SOCKETMESSAGE; //由消息CM_SOCKETMESSAGE触发的过程是过程
//TCustomWinSocket.CMSocketMessage(var Message: TCMSocketMessage);
Wnd := Handle;
end;
WSAAsyncSelect(FSocket, Wnd, Msg, Longint(Byte(FAsyncStyles))); //非阻塞模式处理
if FASyncStyles = [] then //阻塞模式
begin
Blocking := 0;
ioctlsocket(FSocket, FIONBIO, Blocking);//阻塞模式处理
end;
end;
4.再看由消息CM_SOCKETMESSAGE触发的过程
procedure TCustomWinSocket.CMSocketMessage(var Message: TCMSocketMessage);
begin
with Message do
if CheckError then
case SelectEvent of
FD_CONNECT: Connect(Socket);
FD_CLOSE: Disconnect(Socket);
FD_READ: Read(Socket); //触发Read事件
FD_WRITE: Write(Socket); //触发Write事件
FD_ACCEPT: Accept(Socket);
end;
end;
现在应该明白为什么在阻塞模式下不触发OnRead和OnWrite事件了吧？
