TServerSocket：如何在发送消息之前检查ListView上的特定客户端是否仍处于连接状态？
无需检查连接。如果客户端实际上已断开连接，则在触发处理程序Connections[]时，该客户端将不再位于服务器列表中OnTimer。您应该为OnClientDisconnect分配了处理程序，以TServerSocket从中删除客户端TListView。
如果由于某种原因，客户端仍在Connections[]列表中（即，由于基础连接已丢失但TServerSocket尚未检测到），则套接字将仅缓存所有传出数据，直到其出站缓冲区填满为止，然后将开始WSAWOULDBLOCK为每个发送返回错误。最终，操作系统将使死连接超时并TServerSocket从Connections[]列表中将其删除，从而触发OnClientDisconnect事件。
至少，在显示的代码中，应将send循环更新为Close()实际上无法发送的任何套接字，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;