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?

TServerSocket: How check if a specific client on ListView still is connected before send message?

我有一个 Timer 并想向 ListView 的每个客户端发送消息以确定 ping 时间等。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,检查客户端是否真的已连接或类似情况可能更合适。怎么做这个?提前致谢。

无需检查连接。如果客户端实际上已断开连接,则当您的 OnTimer 处理程序被触发时,它不会再出现在服务器的 Connections[] 列表中。您应该将 OnClientDisconnect 处理程序分配给 TServerSocket 以从 TListView.

中删除客户端

如果由于某种原因,客户端仍在 Connections[] 列表中(即,因为基础连接已丢失但 TServerSocket 尚未检测到),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,然后它将开始为每次发送返回 WSAWOULDBLOCK 错误。最终,OS 将使死连接超时,TServerSocket 会将其从 Connections[] 列表中删除,触发 OnClientDisconnect 事件。

至少,在您显示的代码中,您应该将发送循环更新为 Close() 任何实际发送失败的套接字,从而触发 OnClientDisconnect 事件以删除该客户端来自 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;