如何用TIdTelnet抑制回声？ [英] How to supress echo with TIdTelnet?

问题描述

使用Indy10-DelphiXE。
如何使用 TIdTelnet 告诉正在连接的telnet服务器不回显我发送给telnet服务器的命令？

这是我当前的尝试（不起作用），我尝试在每次telnet写入时发送序列IAC DO SUPPRESS_LOCAL_ECHO，但是我确实认为这必须在协商阶段完成？

 使用
 TIdTelnet，
 
 ... 
过程TIOTelnetConnection.SendSupressEcho; 
 
 var 
响应：TIdBytes; 
 
开始
 SetLength（Resp，3）; 
 Resp [0]：= TNC_IAC; 
 Resp [1]：= TNC_DO; 
 Resp [2]：= TNO_SUPLOCALECHO; 
 FIOConnection.IOHandler.Write（Resp）; 
结尾； 
 
过程TIOTelnetConnection.Write（Str：AnsiString）; 
开始
 SendSupressEcho;如果Str<>为
 ’然后
 FIOConnection.IOHandler.Write（Str）; 
结尾； 
  

看着 TIdTelnet 源，我看到了协商过程，但是受到保护，如何覆盖它的行为？

解决方案

如果服务器向您发送 IAC WILL ECHO ，则 TIdTelnet 会硬编码为发送 IAC DO ECHO 响应，然后触发 OnTelnetCommand（tncNoLocalEcho）事件，告诉您不要在本地回显您发送的内容。 / p>

如果服务器向您发送 IAC WONT ECHO ，则 TIdTelnet 被硬编码为发送 IAC DONT ECHO 响应，然后触发 OnTelnetCommand（tncLocalEcho）事件

如果服务器向您发送 IAC DO ECHO ，则 TIdTelnet 被硬编码为发送 IAC WILL ECHO 响应，然后触发 OnTelnetCommand（tncEcho ）事件告诉您回显

如果服务器向您发送 IAC DONT ECHO ，则 TIdTelnet 被硬编码为发送 IAC WONT ECHO 响应，然后触发 OnTelnetCommand（tncLocalEcho）事件，告诉您回显收到的任何内容。

因此，如果您不希望服务器回显您，则可以发送 IAC DONT ECHO 命令发送到服务器，而不是 IAC DO SUPLOCALECHO 命令。然后，服务器将相应地返回 IAC WONT ECHO 或 IAC WILL ECHO （显然是 TIdTelnet 随后将进行答复，但服务器将不会再次响应，因为其 ECHO 当前状态不会更改，从而避免了无休止的响应循环）。

Using Indy10 - DelphiXE. How do I tell the telnet server I am connecting to with TIdTelnet to not echo the commands I send towards the telnet server?

This is my current attempt (which doesn't work), I try to send the sequence IAC DO SUPPRESS_LOCAL_ECHO on each telnet write but I do believe this has to be done in the negotiating phase?

uses
  TIdTelnet,

...
procedure TIOTelnetConnection.SendSupressEcho;

var
  Resp: TIdBytes;

begin
 SetLength(Resp, 3);
 Resp[0] := TNC_IAC;
 Resp[1] := TNC_DO;
 Resp[2] := TNO_SUPLOCALECHO;
 FIOConnection.IOHandler.Write(Resp);
end;

procedure TIOTelnetConnection.Write(Str: AnsiString);
begin
 SendSupressEcho;
 if Str <> '' then
  FIOConnection.IOHandler.Write(Str);
end;

looking at the TIdTelnet source I see the Negotiate procedure, but it is protected, how can I override it's behaviour?

解决方案

If the server sends an IAC WILL ECHO to you, TIdTelnet is hard-coded to send an IAC DO ECHO response, and then triggers an OnTelnetCommand(tncNoLocalEcho) event to tell you not to locally echo what you send.

If the server sends an IAC WONT ECHO to you, TIdTelnet is hard-coded to send an IAC DONT ECHO response, and then triggers an OnTelnetCommand(tncLocalEcho) event to tell you to locally echo what you send.

If the server sends an IAC DO ECHO to you, TIdTelnet is hard-coded to send an IAC WILL ECHO response, and then triggers an OnTelnetCommand(tncEcho) event to tell you to echo back whatever you receive.

If the server sends an IAC DONT ECHO to you, TIdTelnet is hard-coded to send an IAC WONT ECHO response, and then triggers an OnTelnetCommand(tncLocalEcho) event to tell you to echo back whatever you receive.

So, if you don't want the server to echo back to you, you can send an IAC DONT ECHO command to the server, not an IAC DO SUPLOCALECHO command. The server will then reply with either IAC WONT ECHO or IAC WILL ECHO accordingly (which apparently TIdTelnet will then reply to, but the server will not respond back again since its ECHO current state does not change, avoiding an endless response loop).

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