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
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()	Returns the telnet connection input stream.
boolean	getLocalOptionState(int option)	Returns the state of the option on the local side.
OutputStream	getOutputStream()	Returns the telnet connection output stream.
boolean	getReaderThread()	Gets the status of the reader thread.
boolean	getRemoteOptionState(int option)	Returns 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 flag)	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, 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

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()

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:

• 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

unregisterNotifHandler

public void unregisterNotifHandler()

Unregisters the current notification handler.