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From "Shlomy Reinstein (JIRA)" <j...@apache.org>
Subject [jira] Commented: (NET-89) [net] TelnetClient broken for binary transmissions + solution
Date Sun, 22 Nov 2009 12:26:39 GMT

    [ https://issues.apache.org/jira/browse/NET-89?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12781119#action_12781119
] 

Shlomy Reinstein commented on NET-89:
-------------------------------------

I have a different case in which the ToNetASCIIInputStream causes a problem. I use text transmissions,
not binary, however the telnet server does not seem to tell the difference between '\r' and
'\n', and so the replacement of '\n' with "\r\n" causes every line I send to generate an extra
newline, which prevents automation (e.g. in the login/password sequence, the password is always
passed as empty due to the extra newline).

I suggest to add a method like the "setNetASCIIConversion(boolean)" above, and even have a
dedicated one for the just the telnet's output - i.e. avoid only the wrapper ToNetASCIIOutputStream.
Something like:

public void setNetASCIIConversionOnOutput(boolean b);
public void setNetASCIIConversionOnInput(boolean b);

The "set" functions can be replaced by "disable" if the default is to have them enabled. Another
option, which seems better to me, is to replace these functions with new TelnetClient constructors
that take an additional boolean parameter (or two), to ensure this is configured before the
connection is made.

Thanks,
Shlomy

> [net] TelnetClient broken for binary transmissions + solution
> -------------------------------------------------------------
>
>                 Key: NET-89
>                 URL: https://issues.apache.org/jira/browse/NET-89
>             Project: Commons Net
>          Issue Type: Bug
>         Environment: Operating System: All
> Platform: All
>            Reporter: Colin Surprenant
>
> TelnetClient does not handle correctly binary transmissions in two places:
> First in TelnetClient#_connectAction_() the telnet input and output streams are
> wrapped in the NetASCII streams to handle net vs platform line separator
> conversion which breaks the binary data. My quick solution was to simply remove
> those two wrapping streams. A more general solution might be to provide access
> to the unfilterer stream with methods like getUnfilteredInputStream and
> getUnfilteredOutputStream or to dynamically stop the NetASCII stream from
> 'corrupting' the stream when a TelnetOption.BINARY option is negotiated.
> Also, in TelnetInoutStream#__read() there is a bug in the __receiveState
> handling for the _STATE_IAC state. When a second consecutive IAC (0x255) is
> received to encode the single 0x255 character, read does not return 0x255 but
> instead move on to reading the next char in the stream.
> The current code reads:
> case _STATE_IAC:
>     switch (ch)
>     {
>     case TelnetCommand.WILL:
>         __receiveState = _STATE_WILL;
>         continue;
>     case TelnetCommand.WONT:
>         __receiveState = _STATE_WONT;
>         continue;
>     case TelnetCommand.DO:
>         __receiveState = _STATE_DO;
>         continue;
>     case TelnetCommand.DONT:
>         __receiveState = _STATE_DONT;
>         continue;
>     /* TERMINAL-TYPE option (start)*/
>     case TelnetCommand.SB:
>         __suboption_count = 0;
>         __receiveState = _STATE_SB;
>         continue;
>     /* TERMINAL-TYPE option (end)*/
>     case TelnetCommand.IAC:
>         __receiveState = _STATE_DATA;
>         break;
>     default:
>         break;
>     }
>     __receiveState = _STATE_DATA;
>     continue;
> case _STATE_WILL:
> but it should be:
> case _STATE_IAC:
>     switch (ch)
>     {
>     case TelnetCommand.WILL:
>         __receiveState = _STATE_WILL;
>         continue;
>     case TelnetCommand.WONT:
>         __receiveState = _STATE_WONT;
>         continue;
>     case TelnetCommand.DO:
>         __receiveState = _STATE_DO;
>         continue;
>     case TelnetCommand.DONT:
>         __receiveState = _STATE_DONT;
>         continue;
>     /* TERMINAL-TYPE option (start)*/
>     case TelnetCommand.SB:
>         __suboption_count = 0;
>         __receiveState = _STATE_SB;
>         continue;
>     /* TERMINAL-TYPE option (end)*/
>     case TelnetCommand.IAC:
>         __receiveState = _STATE_DATA;
>         break; // exit to enclosing switch to return from read
>     default:
>         __receiveState = _STATE_DATA;           
>         continue; // move on the next char
>     }
>     break; // exit and return from read
> case _STATE_WILL:
> I'll provide patches for this.
> Colin.

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