delphi - Delphi XE2/Indy TIdTCPServer/“对等方重置连接”

我在Delphi XE2中使用Indy来使用TIdTCPServer发送TCP消息时遇到一个问题。

举个例子：
我有2台设备，我将与设备1进行通信。
当我向设备1发送消息时，消息发送正常。
但是没有关闭程序，当我向设备2发送消息时，Delphi返回“对等连接重置”。

下面是我的代码：

procedure TMainHost.idTCPServerNewConnect(AContext: TIdContext);
var
  Client: TSimpleClient;
begin
  Sleep(1000);
  Client := TSimpleClient.Create();

  Client.DNS := AContext.Connection.Socket.Host;
  Client.Conectado := True;
  Client.Port := idTCPServerNew.DefaultPort;
  Client.Name := 'Central';
  Client.ListLink := Clients.Count;
  Client.Thread := AContext;
  Client.IP := AContext.Connection.Socket.Binding.PeerIP;

  AContext.Data := Client;

  Clients.Add(Client);
  Sleep(500);

  if (MainEstrutura.current_central.IP = Client.IP) then
  begin
    MainEstrutura.current_central.Conectado := true;
    MainEstrutura.envia_configuracao;
  end;

end;

procedure TMainHost.idTCPServerNewDisconnect(AContext: TIdContext);
var
  Client: TSimpleClient;
begin
  { Retrieve Client Record from Data pointer }
  Client := Pointer(AContext.Data);
  { Remove Client from the Clients TList }
  Clients.Remove(Client);
  { Free the Client object }
  FreeAndNil(Client);
  AContext.Data := nil;

end;

要将消息发送到设备：

procedure TMainHost.DirectTCPMessage(IP: String; TheMessage: String);
var
  Client: TSimpleClient;
  i: Integer;
  List: TList;
  Msg: String;
begin

  Msg := Trim(TheMessage);

  for i := 0 to Clients.Count - 1 do
  begin

    Client := TSimpleClient(Clients.Items[i]);

    if TIdContext(Client.Thread).Connection.Socket.Binding.PeerIP = IP then
    begin

      TIdContext(Client.Thread).Connection.Socket.WriteLn(Msg);

    end;

  end;
end;

我还有另一个问题。

当我在tidtcpserver组件上设置active：= False时，应用程序崩溃。
谢谢！

最佳答案

您的Clients列表不受多线程访问的保护。 TIdTCPServer是一个多线程组件，每个客户端都在其自己的工作线程中运行。您需要考虑到这一点。我建议您完全摆脱Clients列表，而改用TIdTCPServer.Contexts属性。否则，您需要保护您的Clients列表，例如将其更改为TThreadList，或至少用TCriticalSection将其包装（这是TThreadList在内部执行的操作）。

我看到的另一个问题是，您将Client.DNS字段设置为错误的值，这可能会影响您的通信，具体取决于您正使用的Client.DNS。

尝试以下方法：

procedure TMainHost.idTCPServerNewConnect(AContext: TIdContext);
var
  Client: TSimpleClient;
begin
  Client := TSimpleClient.Create();

  Client.IP := AContext.Binding.PeerIP;
  Client.DNS := GStack.HostByAddress(Client.IP, AContext.Binding.IPVersion);
  Client.Conectado := True;
  Client.Port := AContext.Binding.Port;
  Client.Name := 'Central';
  Client.Thread := AContext;

  AContext.Data := Client;

  // this may or may not need to be Synchronized, depending on what it actually does...
  if (MainEstrutura.current_central.IP = Client.IP) then
  begin
    MainEstrutura.current_central.Conectado := true;
    MainEstrutura.envia_configuracao;
  end;
end;

procedure TMainHost.idTCPServerNewDisconnect(AContext: TIdContext);
var
  Client: TSimpleClient;
begin
  { Retrieve Client Record from Data pointer }
  Client := TSimpleClient(AContext.Data);
  { Free the Client object }
  FreeAndNil(Client);
  AContext.Data := nil;
end;

procedure TMainHost.DirectTCPMessage(IP: String; TheMessage: String);
var
  List: TIdContextList; // or TList in an earlier version that did not have TIdContextList yet
  Context: TIdContext;
  i: Integer;
  Msg: String;
begin
  Msg := Trim(TheMessage);

  List := idTCPServerNew.Contexts.LockList;
  try
    for i := 0 to List.Count - 1 do
    begin
      Context := Context(List[i]);
      if TSimpleClient(Context.Data).IP = IP then
      begin
        try
          Context.Connection.IOHandler.WriteLn(Msg);
        except
        end;
        Break;
      end;
    end;
  finally
    idTCPServerNew.Contexts.UnlockList;
  end;
end;

话虽如此，如果您的服务器从OnExecute事件或CommandsHandlers集合内部发送任何数据，则这种从其线程外部向客户端发送消息的方法并不安全，因为您可能会重叠数据，从而破坏与该客户的沟通。一种更安全的方法是将传出的数据排队，并在安全的情况下让OnExecute事件发送数据，例如：

procedure TMainHost.idTCPServerNewConnect(AContext: TIdContext);
var
  Client: TSimpleClient;
begin
  Client := TSimpleClient.Create();
  ...
  Client.Queue := TIdThreadSafeStringList.Create; // <-- add this
  ...
end;

procedure TMainHost.idTCPServerNewExecute(AContext: TIdContext);
var
  List: TStringList;
  I: Integer;
begin
  Client := TSimpleClient(AContext.Data);
  ...
  List := Client.Queue.Lock;
  try
    while List.Count > 0 do
    begin
      AContext.Connection.IOHandler.WriteLn(List[0]);
      List.Delete(0);
    end;
  finally
    Client.Queue.Unlock;
  end;
  ...
end;

procedure TMainHost.DirectTCPMessage(IP: String; TheMessage: String);
var
  List: TIdContextList; // or TList in an earlier version that did not have TIdContextList yet
  Context: TIdContext;
  i: Integer;
  Msg: String;
begin
  Msg := Trim(TheMessage);

  List := idTCPServerNew.Contexts.LockList;
  try
    for i := 0 to List.Count - 1 do
    begin
      Context := Context(List[i]);
      if TSimpleClient(Context.Data).IP = IP then
      begin
        TSimpleClient(Context.Data).Queue.Add(Msg);
        Break;
      end;
    end;
  finally
    idTCPServerNew.Contexts.UnlockList;
  end;
end;

更新：话虽如此，我建议从TSimpleClient派生TIdServerContext并将其分配给服务器的ContextsClass属性，然后您就不再需要使用TIdContext.Data属性：

type
  TSimpleClient = class(TIdServerContext)
  public
    Queue: TIdThreadSafeStringList;
    ...
    // or TThreadList in an earlier version that did not have TIdContextThreadList yet
    constructor Create(AConnection: TIdTCPConnection; AYarn: TIdYarn; AList: TIdContextThreadList = nil); override;
    destructor Destroy; override;
  end;

constructor TSimpleClient.Create(AConnection: TIdTCPConnection; AYarn: TIdYarn; AList: TIdContextThreadList = nil);
begin
  inherited;
  Queue := TIdThreadSafeStringList.Create;
  ...
end;

destructor TSimpleClient.Destroy;
begin
  ...
  Queue.Free;
  inherited;
end;

procedure TMainHost.FormCreate(Sener: TObject);
begin
  // this must be assigned before the server is activated
  idTCPServerNew.ContextClass := TSimpleClient;
end;

procedure TMainHost.idTCPServerNewConnect(AContext: TIdContext);
var
  Client: TSimpleClient;
  ...
 begin
  Client := AContext as TSimpleClient;
  // use Client as needed...
end;

procedure TMainHost.idTCPServerNewExecute(AContext: TIdContext);
var
  Client: TSimpleClient;
  ...
begin
  Client := AContext as TSimpleClient;
  // use Client as needed...
end;

procedure TMainHost.DirectTCPMessage(IP: String; TheMessage: String);
var
  List: TIdContextList; // or TList in an earlier version that did not have TIdContextList yet
  Client: TSimpleClient;
  i: Integer;
  Msg: String;
begin
  Msg := Trim(TheMessage);

  List := idTCPServerNew.Contexts.LockList;
  try
    for i := 0 to List.Count - 1 do
    begin
      Client := TIdContext(Context(List[i])) as TSimpleClient;
      if Client.IP = IP then
      begin
        Client.Queue.Add(Msg);
        Break;
      end;
    end;
  finally
    idTCPServerNew.Contexts.UnlockList;
  end;
end;