Package org.apache.commons.net.telnet

# Class TelnetClient

java.lang.Object
org.apache.commons.net.SocketClient
org.apache.commons.net.telnet.TelnetClient

public class TelnetClient extends SocketClient
The TelnetClient class implements the simple network virtual terminal (NVT) for the Telnet protocol according to RFC 854. It does not implement any of the extra Telnet options because it is meant to be used within a Java program providing automated access to Telnet accessible resources.

The class can be used by first connecting to a server using the SocketClient `connect` method. Then an InputStream and OutputStream for sending and receiving data over the Telnet connection can be obtained by using the `getInputStream()` and `getOutputStream()` methods. When you finish using the streams, you must call `disconnect` rather than simply closing the streams.

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `protected boolean`
  `readerThread`
  Whether to enable the reader thread.
  `protected static final int`
  `TERMINAL_TYPE`
  Terminal type option
  `protected static final int`
  `TERMINAL_TYPE_IS`
  Is (for subnegotiation)
  `protected static final int`
  `TERMINAL_TYPE_SEND`
  Send (for subnegotiation)

  ### Fields inherited from class org.apache.commons.net.SocketClient

  `_defaultPort_, _hostname_, _input_, _output_, _serverSocketFactory_, _socket_, _socketFactory_, _timeout_, connectTimeout, NETASCII_EOL, remoteInetSocketAddress`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `TelnetClient()`
  Default TelnetClient constructor, sets terminal-type `VT100`.
  `TelnetClient(int maxSubnegotiationLength)`
  Constructs an instance with the specified max subnegotiation length and the default terminal-type `VT100`.
  `TelnetClient(String termtype)`
  Constructs an instance with the specified terminal type.
  `TelnetClient(String termType, int maxSubnegotiationLength)`
  Constructs an instance with the specified terminal type and max subnegotiation length

- ## Method Summary

  Modifier and Type
  Method
  Description
  `protected void`
  `_connectAction_()`
  Handles special connection requirements.
  `void`
  `addOptionHandler(TelnetOptionHandler opthand)`
  Registers a new TelnetOptionHandler for this Telnet client to use.
  `void`
  `deleteOptionHandler(int optcode)`
  Unregisters a TelnetOptionHandler.
  `void`
  `disconnect()`
  Disconnects the Telnet session, closing the input and output streams as well as the socket.
  `InputStream`
  `getInputStream()`
  Gets the Telnet connection input stream.
  `boolean`
  `getLocalOptionState(int option)`
  Gets the state of the option on the local side.
  `OutputStream`
  `getOutputStream()`
  Gets the Telnet connection output stream.
  `boolean`
  `getReaderThread()`
  Gets the status of the reader thread.
  `boolean`
  `getRemoteOptionState(int option)`
  Gets the state of the option on the remote side.
  `void`
  `registerInputListener(TelnetInputListener listener)`
  Register a listener to be notified when new incoming data is available to be read on the `input stream`.
  `void`
  `registerNotifHandler(TelnetNotificationHandler notifhand)`
  Registers a notification handler to which will be sent notifications of received Telnet option negotiation commands.
  `void`
  `registerSpyStream(OutputStream spystream)`
  Registers an OutputStream for spying what's going on in the TelnetClient session.
  `boolean`
  `sendAYT(long timeout)`
  Deprecated.
  Use `sendAYT(Duration)`.
  `boolean`
  `sendAYT(Duration timeout)`
  Sends an `Are You There (AYT)` sequence and waits for the result.
  `void`
  `sendCommand(byte command)`
  Sends a command byte to the remote peer, adding the IAC prefix.
  `void`
  `sendSubnegotiation(int[] message)`
  Sends a protocol-specific subnegotiation message to the remote peer.
  `void`
  `setReaderThread(boolean readerThread)`
  Sets the status of the reader thread.
  `void`
  `stopSpyStream()`
  Stops spying this TelnetClient.
  `void`
  `unregisterInputListener()`
  Unregisters the current `TelnetInputListener`, if any.
  `void`
  `unregisterNotifHandler()`
  Unregisters the current notification handler.

  ### Methods inherited from class org.apache.commons.net.SocketClient

  `addProtocolCommandListener, applySocketAttributes, checkOpenOutputStream, connect, connect, connect, connect, connect, connect, createCommandSupport, fireCommandSent, fireReplyReceived, getCharset, getCharsetName, getCommandSupport, getConnectTimeout, getDefaultPort, getDefaultTimeout, getHostAddress, getHostAddress, getKeepAlive, getLocalAddress, getLocalPort, getProxy, getReceiveBufferSize, getRemoteAddress, getRemoteInetSocketAddress, getRemotePort, getSendBufferSize, getServerSocketFactory, getSoLinger, getSoTimeout, getTcpNoDelay, isAvailable, isConnected, removeProtocolCommandListener, setCharset, setConnectTimeout, setDefaultPort, setDefaultTimeout, setKeepAlive, setProxy, setReceiveBufferSize, setSendBufferSize, setServerSocketFactory, setSocketFactory, setSoLinger, setSoTimeout, setTcpNoDelay, verifyRemote`

  ### Methods inherited from class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Field Details

  - ### readerThread

    protected boolean readerThread
    Whether to enable the reader thread.

  - ### TERMINAL_TYPE

    protected static final int TERMINAL_TYPE
    Terminal type option
    See Also:
      - Constant Field Values

  - ### TERMINAL_TYPE_SEND

    protected static final int TERMINAL_TYPE_SEND
    Send (for subnegotiation)
    See Also:
      - Constant Field Values

  - ### TERMINAL_TYPE_IS

    protected static final int TERMINAL_TYPE_IS
    Is (for subnegotiation)
    See Also:
      - Constant Field Values

- ## Constructor Details

  - ### TelnetClient

    public TelnetClient()
    Default TelnetClient constructor, sets terminal-type `VT100`.

  - ### TelnetClient

    public TelnetClient(int maxSubnegotiationLength)
    Constructs an instance with the specified max subnegotiation length and the default terminal-type `VT100`.
    Parameters:
      `maxSubnegotiationLength` - the size of the subnegotiation buffer.

  - ### TelnetClient

    public TelnetClient(String termtype)
    Constructs an instance with the specified terminal type.
    Parameters:
      `termtype` - the terminal type to use, e.g. `VT100`

  - ### TelnetClient

    public TelnetClient(String termType, int maxSubnegotiationLength)
    Constructs an instance with the specified terminal type and max subnegotiation length
    Parameters:
      `termType` - the terminal type to use, e.g. `VT100`
      `maxSubnegotiationLength` - the size of the subnegotiation buffer

- ## Method Details

  - ### _connectAction_

    protected void _connectAction_() throws IOException
    Handles special connection requirements.
    Throws:
      `IOException` - If an error occurs during connection setup.

  - ### addOptionHandler

    public void addOptionHandler(TelnetOptionHandler opthand) throws InvalidTelnetOptionException, IOException
    Registers a new TelnetOptionHandler for this Telnet client to use.
    Parameters:
      `opthand` - option handler to be registered.
    Throws:
      `InvalidTelnetOptionException` - on error
      `IOException` - on error

  - ### deleteOptionHandler

    public void deleteOptionHandler(int optcode) throws InvalidTelnetOptionException, IOException
    Unregisters a TelnetOptionHandler.
    Parameters:
      `optcode` - Code of the option to be unregistered.
    Throws:
      `InvalidTelnetOptionException` - on error
      `IOException` - on error

  - ### disconnect

    public void disconnect() throws IOException
    Disconnects the Telnet session, closing the input and output streams as well as the socket. If you have references to the input and output streams of the Telnet connection, you should not close them yourself, but rather call disconnect to properly close the connection.
    Overrides:
      `disconnect` in class `SocketClient`
    Throws:
      `IOException` - not thrown, subclasses may throw.

  - ### getInputStream

    public InputStream getInputStream()
    Gets the Telnet connection input stream. You should not close the stream when you finish with it. Rather, you should call `disconnect` .
    Returns:
      The Telnet connection input stream.

  - ### getLocalOptionState

    public boolean getLocalOptionState(int option)
    Gets the state of the option on the local side.
    Parameters:
      `option` - Option to be checked.
    Returns:
      The state of the option on the local side.

  - ### getOutputStream

    public OutputStream getOutputStream()
    Gets the Telnet connection output stream. You should not close the stream when you finish with it. Rather, you should call `disconnect` .
    Returns:
      The Telnet connection output stream.

  - ### getReaderThread

    public boolean getReaderThread()
    Gets the status of the reader thread.
    Returns:
      true if the reader thread is enabled, false otherwise

  - ### getRemoteOptionState

    public boolean getRemoteOptionState(int option)
    Gets the state of the option on the remote side.
    Parameters:
      `option` - Option to be checked.
    Returns:
      The state of the option on the remote side.

  - ### registerInputListener

    public void registerInputListener(TelnetInputListener listener)
    Register a listener to be notified when new incoming data is available to be read on the `input stream`. Only one listener is supported at a time.

    More precisely, notifications are issued whenever the number of bytes available for immediate reading (i.e., the value returned by `InputStream.available()`) transitions from zero to non-zero. Note that (in general) multiple reads may be required to empty the buffer and reset this notification, because incoming bytes are being added to the internal buffer asynchronously.

    Notifications are only supported when a `reader thread` is enabled for the connection.

    Parameters:
      `listener` - listener to be registered, replaces any previous listener.
    Since:
      3.0

  - ### registerSpyStream

    public void registerSpyStream(OutputStream spystream)
    Registers an OutputStream for spying what's going on in the TelnetClient session.
    Parameters:
      `spystream` - OutputStream on which session activity will be echoed.

  - ### sendAYT

    public boolean sendAYT(Duration timeout) throws IOException, IllegalArgumentException, InterruptedException
    Sends an `Are You There (AYT)` sequence and waits for the result.
    Parameters:
      `timeout` - Time to wait for a response.
    Returns:
      true if AYT received a response, false otherwise.
    Throws:
      `InterruptedException` - on error
      `IllegalArgumentException` - on error
      `IOException` - on error
    Since:
      3.10.0

  - ### sendAYT

    @Deprecated public boolean sendAYT(long timeout) throws IOException, IllegalArgumentException, InterruptedException
    Deprecated.
    Use `sendAYT(Duration)`.
    Sends an `Are You There (AYT)` sequence and waits for the result.
    Parameters:
      `timeout` - Time to wait for a response (millis.)
    Returns:
      true if AYT received a response, false otherwise
    Throws:
      `InterruptedException` - on error
      `IllegalArgumentException` - on error
      `IOException` - on error

  - ### sendCommand

    public void sendCommand(byte command) throws IOException, IllegalArgumentException
    Sends a command byte to the remote peer, adding the IAC prefix.

    This method does not wait for any response. Messages sent by the remote end can be handled by registering an approrpriate `TelnetOptionHandler`.

    Parameters:
      `command` - the code for the command
    Throws:
      `IOException` - if an I/O error occurs while writing the message
      `IllegalArgumentException` - on error
    Since:
      3.0

  - ### sendSubnegotiation

    public void sendSubnegotiation(int[] message) throws IOException, IllegalArgumentException
    Sends a protocol-specific subnegotiation message to the remote peer. `TelnetClient` will add the IAC SB & IAC SE framing bytes; the first byte in `message` should be the appropriate Telnet option code.

    This method does not wait for any response. Subnegotiation messages sent by the remote end can be handled by registering an approrpriate `TelnetOptionHandler`.

    Parameters:
      `message` - option code followed by subnegotiation payload
    Throws:
      `IllegalArgumentException` - if `message` has length zero
      `IOException` - if an I/O error occurs while writing the message
    Since:
      3.0

  - ### setReaderThread

    public void setReaderThread(boolean readerThread)
    Sets the status of the reader thread.

    When enabled, a seaparate internal reader thread is created for new connections to read incoming data as it arrives. This results in immediate handling of option negotiation, notifications, etc. (at least until the fixed-size internal buffer fills up). Otherwise, no thread is created an all negotiation and option handling is deferred until a read() is performed on the `input stream`.

    The reader thread must be enabled for `TelnetInputListener` support.

    When this method is invoked, the reader thread status will apply to all subsequent connections; the current connection (if any) is not affected.

    Parameters:
      `readerThread` - true to enable the reader thread, false to disable.
    See Also:
      - `registerInputListener(org.apache.commons.net.telnet.TelnetInputListener)`

  - ### stopSpyStream

    public void stopSpyStream()
    Stops spying this TelnetClient.

  - ### unregisterInputListener

    public void unregisterInputListener()
    Unregisters the current `TelnetInputListener`, if any.
    Since:
      3.0

  - ### registerNotifHandler

    public void registerNotifHandler(TelnetNotificationHandler notifhand)
    Registers a notification handler to which will be sent notifications of received Telnet option negotiation commands.
    Parameters:
      `notifhand` - TelnetNotificationHandler to be registered

  - ### unregisterNotifHandler

    public void unregisterNotifHandler()
    Unregisters the current notification handler.