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com2tcp telnet and CR

foss1024
2009-06-20
2013-05-20
  • foss1024

    foss1024 - 2009-06-20

    To the best of my knowledge, telnet clients and servers
    are supposed to encode CR as either CR NULL or CR LF (RFC 854).

    com2tcp --telnet does not appear to do this.
    I have to hit <enter> twice for the CR to be recognized
    by my telnet server.

    This appears to be a common problem with RFC 2217 clients.
    Tactical Software's Serial/IP redirector has a CR-padding mode
    to support this functionality. 

    I'd much rather use an open source product.

    Thank you.

     
    • Vyacheslav Frolov

      The com2tcp suppose the terminal emulation program do adding LF after
      CR itself.
      AFAIK all terminal emulation programs have this option.

       
      • foss1024

        foss1024 - 2009-06-22

        I hadn't looked for the settings, but I now see that if I use Hyperterminal I
        can configure terminal properties in ASCII settings.

        But if I want to use a 3rd party software such as SatMac to talk to
        my Comtech modem (http://www.comtechefdata.com/pcutils.asp),
        I cannot configure it.  It expects to be talking to a serial port and
        the telnet stuff isn't translated.

        Thanks.

         
    • Vyacheslav Frolov

      I can't understand what are you trying to do.
      Could you describe it in more detail.
      Does Comtech modem require telnet protocol?
      Why are you use SatMac?
      Why are you use com2tcp?

       
    • foss1024

      foss1024 - 2009-06-22

      SatMac is a legacy windows application which communicates with local COM
      ports to interact with a Comtech modem.

      I'm trying to use SatMac on my desktop to talk to a Comtech modem at
      a remote location.

      At the remote location, I have a console server which can export it's
      serial ports using the telnet protocol.  SatMac does not understand
      the telnet protocol, so I'm trying to use com2tcp to bridge by desktop
      to the remote location.

      SatMac uses COM5
      COM5:CNCB0             (com0com null modem pair)
      CNCB0 telnets to 10.10.10.10:2000  (using com2tcp)

      com2tcp negotiates telnet options perfectly.  It doesn't translate CR though.

      So SatMac sends a command such as "[CR]<0100/FLT?[CR]" and because it's
      going through telnet, the protocol is eating "<" and preventing the modem
      from seeing it.  The "<" is an important delimiter for the Comtech modem,
      and so it sees the input as garbage and ignores it.

      Thank you.

       
    • Vyacheslav Frolov

      What is a console server?
      Send me a console output of com2tcp.
      Does your console server supports TRANSMIT-BINARY option of telnet protocol?
      What operating system is at the remote location?
      Why you not use com2tcp instead the console server?

       
      • foss1024

        foss1024 - 2009-06-23

        http://en.wikipedia.org/wiki/Console_server
        Basically, it's a server with a bunch of serial ports that allow access to
        devices from a remote location.

        The console server I'm using is built for security and does not allow
        software to be installed.  It is chosen for it's security features.

        Their software does not yet support the Binary telnet option, so it's
        restricted to mostly 7-bit data.

        C:\com0com\com2tcp-1.3.0.0-386>com2tcp --telnet \\.\CNCB0 10.10.10.10 2000
        OpenC0C("\\.\CNCB0", baud=19200, data=8, parity=no, stop=1) - OK
        DSR is ON
        WaitComReady() - OK
        Connect("10.10.10.10", "2000") - OK
        InOut() START
        DSR is ON
        RECV: WILL 1
        SEND: DO 1
        RECV: DONT 1
        RECV: DO 31
        SEND: WONT 31
        RECV: WILL 3
        SEND: DONT 3
        RECV: DO 3
        SEND: WONT 3
        RECV: DO 24
        SEND: WILL 24
        RECV: SB 24
          1 SE
        SEND: SB 24
          0 85 78 75 78 79 87 78 SE
        RECV: DONT 34

        Thank you.

         
  • Vyacheslav Frolov

    This feature added to hub4com's telnet filter (CVS version).

    Example (encode CR as CR LF):

    hub4com ... --create-filter=telnet:--ascii-cr-padding=0A ...
    
     
  • Anonymous

    Anonymous - 2011-10-24

    I need to know something. Is Telnet the only TCP/IP protocol com2tcp will support? What I would like to do is connect a virtual RS-232 serial port to a binary (custom protocol) TCP/IP socket if at all possible. Thank you…

     
  • Vyacheslav Frolov

    With com2tcp or hub4com a virtual serial port can be connected to TCP/IP socket with Telnet protocol or without protocol (raw binary). Additionally the hub4com allows to add other protocols (plug-in modules).

     
  • Anonymous

    Anonymous - 2011-10-25

    This is good to know. Thanks.

     

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