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From "Archie Cobbs (JIRA)" <>
Subject [jira] Created: (NET-343) Telnet client: Support Client-initiated Subnegotiation Messages
Date Fri, 19 Nov 2010 21:13:25 GMT
Telnet client: Support Client-initiated Subnegotiation Messages

                 Key: NET-343
             Project: Commons Net
          Issue Type: New Feature
          Components: Telnet
    Affects Versions: 2.0
            Reporter: Archie Cobbs

I am in the process of trying to implement a Java client for [RFC 2217|],
which is the protocol for accessing serial ports over TCP. Unfortunately, the commons-net
telnet client is insufficient for this relatively simple task.

There are two missing features in the commons-net telnet client code, one of which is a show
stopper and the other of which would be a "real nice to have". This issue documents the first

RFC 2217 specifies that serial port events (such as server notifiying about a change in carrier
detect, or the client instructing the server to change the baud rate) are delivered to the
peer by subnegotiations. For example, to notify the client about carrier detect, the server
sends {{IAC SB COM-PORT-OPTION NOTIFY-MODEMSTATE <value> IAC SE}} to the client; to
set the serial port baud rate, the client sends {{IAC SB COM-PORT-OPTION SET-BAUD <value(4)>
IAC SE}} to the server. These messages can happen at any time and are not associated with
any WILL/WONT/DO/DONT negotiation (according to my understanding).

The problem is that while one can _receive_ such messages via {{TelnetOptionHandler.answerSubnegotiation()}},
the {{TelnetClient}} class doesn't provide any way to _send_ (i.e., intiate) these messages.

What's needed here is simply to expose {{Telnet._sendSubnegotiation()}} (properly renamed,
etc.) as a public method.

I'm going to attempt to come up with a patch and will attach it here if successful.

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