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 Details

    • readerThread

      protected boolean readerThread

    • TERMINAL_TYPE

      protected static final int TERMINAL_TYPE
      Terminal type option
      See Also:

    • TERMINAL_TYPE_SEND

      protected static final int TERMINAL_TYPE_SEND
      Send (for subnegotiation)
      See Also:

    • TERMINAL_TYPE_IS

      protected static final int TERMINAL_TYPE_IS
      Is (for subnegotiation)
      See Also:

  • 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()
      Returns 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)
      Returns 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()
      Returns 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)
      Returns 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
      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

    • 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 flag)
      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:
      flag - true to enable the reader thread, false to disable
      See Also:

    • stopSpyStream

      public void stopSpyStream()
      Stops spying this TelnetClient.

    • unregisterInputListener

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

    • unregisterNotifHandler

      public void unregisterNotifHandler()
      Unregisters the current notification handler.