sockets - TServerSocket:如何在发送消息之前检查 ListView 上的特定客户端是否仍然连接?
问题描述
例如,我有一个Timer
并希望向每个客户端发送一条消息以ListView
确定 ping 时间。然后我有以下代码:
procedure TMainForm.Timer1Timer(Sender: TObject);
var
i: Integer;
begin
try
for i := 0 to ListView1.Items.count - 1 do
begin
ListView1.Items.Item[i].SubItems.Objects[2] := TObject(GetTickCount);
ServerSocket1.Socket.Connections[i].SendText('ping' + #13#10);
end;
except
exit;
end;
end;
在发送之前,可能更适合检查客户端是否真的连接或类似的。这个怎么做?提前致谢。
解决方案
无需检查连接。如果客户端实际上已断开连接,则当您的处理程序被触发时,它将不再位于服务器的Connections[]
列表中。OnTimer
您应该有一个OnClientDisconnect
分配给 的处理程序以TServerSocket
从TListView
.
如果由于某种原因,客户端仍在Connections[]
列表中(即,因为底层连接已丢失但TServerSocket
尚未检测到它),则套接字将简单地缓存所有传出数据,直到其出站缓冲区填满,然后它将开始WSAWOULDBLOCK
为每次发送返回错误。最终,操作系统将超时死连接并将TServerSocket
其从Connections[]
列表中删除,从而触发OnClientDisconnect
事件。
至少,在您显示的代码中,您应该将您的发送循环更新为Close()
任何实际发送失败的套接字,从而触发OnClientDisconnect
事件以从 中删除该客户端TListView
,例如:
procedure TMainForm.ServerSocket1ClientConnect(Sender: TObject; Socket: TCustomWinSocket);
var
Item: TListItem;
begin
Item := ListView1.Items.Add;
Item.Data := Socket;
...
end;
procedure TMainForm.ServerSocket1ClientDisconnect(Sender: TObject; Socket: TCustomWinSocket);
var
Item: TListItem;
begin
Item := ListView1.FindData(0, Socket, True, False);
if Item <> nil then
Item.Delete;
end;
procedure TMainForm.Timer1Timer(Sender: TObject);
const
s: AnsiString = 'ping' + #13#10;
var
Item: TListItem;
Socket: TCustomWinSocket;
p: PAnsiChar;
i, len, sent: Integer;
begin
for i := 0 to ListView1.Items.Count - 1 do
begin
Item := ListView1.Items[i];
Item.SubItems.Objects[2] := TObject(GetTickCount);
Socket := TCustomWinSocket(Item.Data);
try
// SendText() does not handle partial sends, or Unicode strings...
//Socket.SendText('ping' + #13#10);
p := PAnsiChar(s);
len := Length(s);
repeat
sent := Socket.SendBuf(p^, len);
if sent = -1 then
being
if WSAGetLastError() <> WSAEWOULDBLOCK then
Break;
// TODO: stop trying after several attempts fail...
Continue;
end;
Inc(p, sent);
Dec(len, sent);
until len = 0;
if len = 0 then
Continue;
except
end;
Socket.Close;
end;
end;