/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *      https://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.apache.commons.net.telnet;
  
  import java.io.BufferedInputStream;
  import java.io.BufferedOutputStream;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.time.Duration;
  import java.util.Arrays;
  
  import org.apache.commons.net.SocketClient;
  
  class Telnet extends SocketClient {
      static final boolean debug = /* true; */ false;
  
      static final boolean debugoptions = /* true; */ false;
  
      static final byte[] COMMAND_DO = { (byte) TelnetCommand.IAC, (byte) TelnetCommand.DO };
  
      static final byte[] COMMAND_DONT = { (byte) TelnetCommand.IAC, (byte) TelnetCommand.DONT };
  
      static final byte[] COMMAND_WILL = { (byte) TelnetCommand.IAC, (byte) TelnetCommand.WILL };
  
      static final byte[] COMMAND_WONT = { (byte) TelnetCommand.IAC, (byte) TelnetCommand.WONT };
  
      static final byte[] COMMAND_SB = { (byte) TelnetCommand.IAC, (byte) TelnetCommand.SB };
  
      static final byte[] COMMAND_SE = { (byte) TelnetCommand.IAC, (byte) TelnetCommand.SE };
  
      static final int WILL_MASK = 0x01;
      static final int DO_MASK = 0x02;
      static final int REQUESTED_WILL_MASK = 0x04;
      static final int REQUESTED_DO_MASK = 0x08;
  
      /* public */
      static final int DEFAULT_PORT = 23;
  
      /* TERMINAL-TYPE option (start) */
      /**
       * Terminal type option
       */
      protected static final int TERMINAL_TYPE = 24;
      /**
       * Send (for subnegotiation)
       */
      protected static final int TERMINAL_TYPE_SEND = 1;
      /**
       * Is (for subnegotiation)
       */
      protected static final int TERMINAL_TYPE_IS = 0;
  
      /**
       * Is sequence (for subnegotiation)
       */
      static final byte[] COMMAND_IS = { (byte) TERMINAL_TYPE, (byte) TERMINAL_TYPE_IS };
  
      /* Code Section added for supporting AYT (start) */
      /**
       * AYT sequence
       */
      static final byte[] COMMAND_AYT = { (byte) TelnetCommand.IAC, (byte) TelnetCommand.AYT };
  
      static final char NUL = '\0';
  
      private final int[] doResponse;
  
      private final int[] willResponse;
  
      private final int[] options;
  
      /* open TelnetOptionHandler functionality (end) */
  
      /**
       * Terminal type
       */
      private String terminalType;
      /* TERMINAL-TYPE option (end) */
  
      /* open TelnetOptionHandler functionality (start) */
      /**
       * Array of option handlers
       */
      private final TelnetOptionHandler[] optionHandlers;
 
     /**
      * monitor to wait for AYT
      */
     private final Object aytMonitor = new Object();
 
     /**
      * flag for AYT
      */
     private volatile boolean aytFlag = true;
     /* Code Section added for supporting AYT (end) */
 
     /**
      * The stream on which to spy
      */
     private volatile OutputStream spyStream;
 
     /**
      * The notification handler
      */
     private TelnetNotificationHandler notifhand;
 
     /**
      * Empty Constructor
      */
     Telnet() {
         setDefaultPort(DEFAULT_PORT);
         doResponse = new int[TelnetOption.MAX_OPTION_VALUE + 1];
         willResponse = new int[TelnetOption.MAX_OPTION_VALUE + 1];
         options = new int[TelnetOption.MAX_OPTION_VALUE + 1];
         optionHandlers = new TelnetOptionHandler[TelnetOption.MAX_OPTION_VALUE + 1];
     }
 
     /* TERMINAL-TYPE option (start) */
     /**
      * This constructor lets you specify the terminal type.
      *
      * @param termtype   terminal type to be negotiated (ej. VT100)
      */
     Telnet(final String termtype) {
         setDefaultPort(DEFAULT_PORT);
         doResponse = new int[TelnetOption.MAX_OPTION_VALUE + 1];
         willResponse = new int[TelnetOption.MAX_OPTION_VALUE + 1];
         options = new int[TelnetOption.MAX_OPTION_VALUE + 1];
         terminalType = termtype;
         optionHandlers = new TelnetOptionHandler[TelnetOption.MAX_OPTION_VALUE + 1];
     }
     /* TERMINAL-TYPE option (end) */
 
     /**
      * Called upon connection.
      *
      * @throws IOException - Exception in I/O.
      */
     @Override
     protected void _connectAction_() throws IOException {
         /* (start). BUGFIX: clean the option info for each connection */
         for (int ii = 0; ii < TelnetOption.MAX_OPTION_VALUE + 1; ii++) {
             doResponse[ii] = 0;
             willResponse[ii] = 0;
             options[ii] = 0;
             if (optionHandlers[ii] != null) {
                 optionHandlers[ii].setDo(false);
                 optionHandlers[ii].setWill(false);
             }
         }
         /* (end). BUGFIX: clean the option info for each connection */
 
         super._connectAction_();
         _input_ = new BufferedInputStream(_input_);
         _output_ = new BufferedOutputStream(_output_);
 
         /* open TelnetOptionHandler functionality (start) */
         for (int ii = 0; ii < TelnetOption.MAX_OPTION_VALUE + 1; ii++) {
             if (optionHandlers[ii] != null) {
                 if (optionHandlers[ii].getInitLocal()) {
                     requestWill(optionHandlers[ii].getOptionCode());
                 }
 
                 if (optionHandlers[ii].getInitRemote()) {
                     requestDo(optionHandlers[ii].getOptionCode());
                 }
             }
         }
         /* open TelnetOptionHandler functionality (end) */
     }
 
     /* Code Section added for supporting spystreams (start) */
     /**
      * Registers an OutputStream for spying what's going on in the Telnet session.
      *
      * @param spystream   OutputStream on which session activity will be echoed.
      */
     void _registerSpyStream(final OutputStream spystream) {
         spyStream = spystream;
     }
 
     /* Code Section added for supporting AYT (start) */
     /**
      * Sends an {@code Are You There (AYT)} sequence and waits for the result.
      *
      * @param timeout   Time to wait for a response.
      * @throws IOException              - Exception in I/O.
      * @throws IllegalArgumentException - Illegal argument
      * @throws InterruptedException     - Interrupted during wait.
      * @return true if AYT received a response, false otherwise
      **/
     final boolean _sendAYT(final Duration timeout) throws IOException, IllegalArgumentException, InterruptedException {
         boolean retValue = false;
         synchronized (aytMonitor) {
             synchronized (this) {
                 aytFlag = false;
                 _output_.write(COMMAND_AYT);
                 _output_.flush();
             }
             aytMonitor.wait(timeout.toMillis());
             if (!aytFlag) {
                 aytFlag = true;
             } else {
                 retValue = true;
             }
         }
 
         return retValue;
     }
     /* Code Section added for supporting AYT (end) */
 
     /**
      * Sends a command, automatically adds IAC prefix and flushes the output.
      *
      * @param cmd   command data to be sent
      * @throws IOException - Exception in I/O.
      * @since 3.0
      */
     final synchronized void _sendCommand(final byte cmd) throws IOException {
         _output_.write(TelnetCommand.IAC);
         _output_.write(cmd);
         _output_.flush();
     }
 
     /* open TelnetOptionHandler functionality (start) */
     /**
      * Manages subnegotiation for Terminal Type.
      *
      * @param subn   subnegotiation data to be sent
      * @throws IOException - Exception in I/O.
      **/
     final synchronized void _sendSubnegotiation(final int[] subn) throws IOException {
         if (debug) {
             System.err.println("SEND SUBNEGOTIATION: ");
             if (subn != null) {
                 System.err.println(Arrays.toString(subn));
             }
         }
         if (subn != null) {
             _output_.write(COMMAND_SB);
             // Note _output_ is buffered, so might as well simplify by writing single bytes
             for (final int element : subn) {
                 final byte b = (byte) element;
                 if (b == (byte) TelnetCommand.IAC) { // cast is necessary because IAC is outside the signed byte range
                     _output_.write(b); // double any IAC bytes
                 }
                 _output_.write(b);
             }
             _output_.write(COMMAND_SE);
 
             /* Code Section added for sending the negotiation ASAP (start) */
             _output_.flush();
             /* Code Section added for sending the negotiation ASAP (end) */
         }
     }
     /* open TelnetOptionHandler functionality (end) */
 
     /**
      * Stops spying this Telnet.
      */
     void _stopSpyStream() {
         spyStream = null;
     }
 
     /**
      * Registers a new TelnetOptionHandler for this Telnet to use.
      *
      * @param opthand   option handler to be registered.
      * @throws InvalidTelnetOptionException - The option code is invalid.
      * @throws IOException                  on error
      **/
     void addOptionHandler(final TelnetOptionHandler opthand) throws InvalidTelnetOptionException, IOException {
         final int optcode = opthand.getOptionCode();
         if (!TelnetOption.isValidOption(optcode)) {
             throw new InvalidTelnetOptionException("Invalid Option Code", optcode);
         }
         if (optionHandlers[optcode] != null) {
             throw new InvalidTelnetOptionException("Already registered option", optcode);
         }
         optionHandlers[optcode] = opthand;
         if (isConnected()) {
             if (opthand.getInitLocal()) {
                 requestWill(optcode);
             }
 
             if (opthand.getInitRemote()) {
                 requestDo(optcode);
             }
         }
     }
 
     /**
      * Unregisters a TelnetOptionHandler.
      *
      * @param optcode   Code of the option to be unregistered.
      * @throws InvalidTelnetOptionException - The option code is invalid.
      * @throws IOException                  on error
      **/
     void deleteOptionHandler(final int optcode) throws InvalidTelnetOptionException, IOException {
         if (!TelnetOption.isValidOption(optcode)) {
             throw new InvalidTelnetOptionException("Invalid Option Code", optcode);
         }
         if (optionHandlers[optcode] == null) {
             throw new InvalidTelnetOptionException("Unregistered option", optcode);
         }
         final TelnetOptionHandler opthand = optionHandlers[optcode];
         optionHandlers[optcode] = null;
 
         if (opthand.getWill()) {
             requestWont(optcode);
         }
 
         if (opthand.getDo()) {
             requestDont(optcode);
         }
     }
     /* open TelnetOptionHandler functionality (end) */
 
     /* Code Section added for supporting AYT (start) */
     /**
      * Processes the response of an AYT
      */
     final synchronized void processAYTResponse() {
         if (!aytFlag) {
             synchronized (aytMonitor) {
                 aytFlag = true;
                 aytMonitor.notifyAll();
             }
         }
     }
     /* Code Section added for supporting AYT (end) */
 
     /**
      * Processes a COMMAND.
      *
      * @param command   option code to be set.
      **/
     void processCommand(final int command) {
         if (debugoptions) {
             System.err.println("RECEIVED COMMAND: " + command);
         }
 
         if (notifhand != null) {
             notifhand.receivedNegotiation(TelnetNotificationHandler.RECEIVED_COMMAND, command);
         }
     }
 
     /**
      * Processes a {@code DO} request.
      *
      * @param option   option code to be set.
      * @throws IOException - Exception in I/O.
      **/
     void processDo(final int option) throws IOException {
         if (debugoptions) {
             System.err.println("RECEIVED DO: " + TelnetOption.getOption(option));
         }
 
         if (notifhand != null) {
             notifhand.receivedNegotiation(TelnetNotificationHandler.RECEIVED_DO, option);
         }
 
         boolean acceptNewState = false;
 
         /* open TelnetOptionHandler functionality (start) */
         if (optionHandlers[option] != null) {
             acceptNewState = optionHandlers[option].getAcceptLocal();
         } else if (option == TERMINAL_TYPE && terminalType != null && !terminalType.isEmpty()) {
             acceptNewState = true;
         }
         /* TERMINAL-TYPE option (end) */
         /* open TelnetOptionHandler functionality (start) */
 
         if (willResponse[option] > 0) {
             --willResponse[option];
             if (willResponse[option] > 0 && stateIsWill(option)) {
                 --willResponse[option];
             }
         }
 
         if (willResponse[option] == 0) {
             if (requestedWont(option)) {
 
                 switch (option) {
 
                 default:
                     break;
 
                 }
 
                 if (acceptNewState) {
                     setWantWill(option);
                     sendWill(option);
                 } else {
                     ++willResponse[option];
                     sendWont(option);
                 }
             } else {
                 // Other end has acknowledged option.
 
                 switch (option) {
 
                 default:
                     break;
 
                 }
 
             }
         }
 
         setWill(option);
     }
 
     /**
      * Processes a {@code DONT} request.
      *
      * @param option   option code to be set.
      * @throws IOException - Exception in I/O.
      **/
     void processDont(final int option) throws IOException {
         if (debugoptions) {
             System.err.println("RECEIVED DONT: " + TelnetOption.getOption(option));
         }
         if (notifhand != null) {
             notifhand.receivedNegotiation(TelnetNotificationHandler.RECEIVED_DONT, option);
         }
         if (willResponse[option] > 0) {
             --willResponse[option];
             if (willResponse[option] > 0 && stateIsWont(option)) {
                 --willResponse[option];
             }
         }
 
         if (willResponse[option] == 0 && requestedWill(option)) {
 
             switch (option) {
 
             default:
                 break;
 
             }
 
             /* FIX for a BUG in the negotiation (start) */
             if (stateIsWill(option) || requestedWill(option)) {
                 sendWont(option);
             }
 
             setWantWont(option);
             /* FIX for a BUG in the negotiation (end) */
         }
 
         setWont(option);
     }
 
     /* TERMINAL-TYPE option (start) */
     /**
      * Processes a suboption negotiation.
      *
      * @param suboption         subnegotiation data received
      * @param suboptionLength   length of data received
      * @throws IOException - Exception in I/O.
      **/
     void processSuboption(final int[] suboption, final int suboptionLength) throws IOException {
         if (debug) {
             System.err.println("PROCESS SUBOPTION.");
         }
 
         /* open TelnetOptionHandler functionality (start) */
         if (suboptionLength > 0) {
             if (optionHandlers[suboption[0]] != null) {
                 final int[] responseSuboption = optionHandlers[suboption[0]].answerSubnegotiation(suboption, suboptionLength);
                 _sendSubnegotiation(responseSuboption);
             } else if (suboptionLength > 1) {
                 if (debug) {
                     for (int ii = 0; ii < suboptionLength; ii++) {
                         System.err.println("SUB[" + ii + "]: " + suboption[ii]);
                     }
                 }
                 if (suboption[0] == TERMINAL_TYPE && suboption[1] == TERMINAL_TYPE_SEND) {
                     sendTerminalType();
                 }
             }
         }
         /* open TelnetOptionHandler functionality (end) */
     }
 
     /**
      * Processes a {@code WILL} request.
      *
      * @param option   option code to be set.
      * @throws IOException - Exception in I/O.
      **/
     void processWill(final int option) throws IOException {
         if (debugoptions) {
             System.err.println("RECEIVED WILL: " + TelnetOption.getOption(option));
         }
 
         if (notifhand != null) {
             notifhand.receivedNegotiation(TelnetNotificationHandler.RECEIVED_WILL, option);
         }
 
         boolean acceptNewState = false;
 
         /* open TelnetOptionHandler functionality (start) */
         if (optionHandlers[option] != null) {
             acceptNewState = optionHandlers[option].getAcceptRemote();
         }
         /* open TelnetOptionHandler functionality (end) */
 
         if (doResponse[option] > 0) {
             --doResponse[option];
             if (doResponse[option] > 0 && stateIsDo(option)) {
                 --doResponse[option];
             }
         }
 
         if (doResponse[option] == 0 && requestedDont(option)) {
 
             switch (option) {
 
             default:
                 break;
 
             }
 
             if (acceptNewState) {
                 setWantDo(option);
                 sendDo(option);
             } else {
                 ++doResponse[option];
                 sendDont(option);
             }
         }
 
         setDo(option);
     }
 
     /**
      * Processes a {@code WONT} request.
      *
      * @param option   option code to be set.
      * @throws IOException - Exception in I/O.
      **/
     void processWont(final int option) throws IOException {
         if (debugoptions) {
             System.err.println("RECEIVED WONT: " + TelnetOption.getOption(option));
         }
 
         if (notifhand != null) {
             notifhand.receivedNegotiation(TelnetNotificationHandler.RECEIVED_WONT, option);
         }
 
         if (doResponse[option] > 0) {
             --doResponse[option];
             if (doResponse[option] > 0 && stateIsDont(option)) {
                 --doResponse[option];
             }
         }
 
         if (doResponse[option] == 0 && requestedDo(option)) {
 
             switch (option) {
 
             default:
                 break;
 
             }
 
             /* FIX for a BUG in the negotiation (start) */
             if (stateIsDo(option) || requestedDo(option)) {
                 sendDont(option);
             }
 
             setWantDont(option);
             /* FIX for a BUG in the negotiation (end) */
         }
 
         setDont(option);
     }
 
     /**
      * Registers a notification handler to which will be sent notifications of received Telnet option negotiation commands.
      *
      * @param notifhand   TelnetNotificationHandler to be registered
      */
     public void registerNotifHandler(final TelnetNotificationHandler notifhand) {
         this.notifhand = notifhand;
     }
 
     /**
      * Requests a DO.
      *
      * @param option   Option code.
      * @throws IOException - Exception in I/O.
      **/
     final synchronized void requestDo(final int option) throws IOException {
         if (doResponse[option] == 0 && stateIsDo(option) || requestedDo(option)) {
             return;
         }
         setWantDo(option);
         ++doResponse[option];
         sendDo(option);
     }
 
     /**
      * Requests a {@code DONT}.
      *
      * @param option   Option code.
      * @throws IOException - Exception in I/O.
      **/
     final synchronized void requestDont(final int option) throws IOException {
         if (doResponse[option] == 0 && stateIsDont(option) || requestedDont(option)) {
             return;
         }
         setWantDont(option);
         ++doResponse[option];
         sendDont(option);
     }
 
     /**
      * Looks for the state of the option.
      *
      * @return true if a {@code DO} has been requested.
      * @param option   option code to be looked up.
      */
     boolean requestedDo(final int option) {
         return (options[option] & REQUESTED_DO_MASK) != 0;
     }
 
     /**
      * Looks for the state of the option.
      *
      * @return true if a {@code DONT} has been requested
      * @param option   option code to be looked up.
      */
     boolean requestedDont(final int option) {
         return !requestedDo(option);
     }
 
     /**
      * Looks for the state of the option.
      *
      * @return true if a {@code WILL} has been requested
      * @param option   option code to be looked up.
      */
     boolean requestedWill(final int option) {
         return (options[option] & REQUESTED_WILL_MASK) != 0;
     }
 
     /**
      * Looks for the state of the option.
      *
      * @return true if a {@code WONT} has been requested
      * @param option   option code to be looked up.
      */
     boolean requestedWont(final int option) {
         return !requestedWill(option);
     }
 
     /**
      * Requests a {@code WILL}.
      *
      * @param option   Option code.
      * @throws IOException - Exception in I/O.
      **/
     final synchronized void requestWill(final int option) throws IOException {
         if (willResponse[option] == 0 && stateIsWill(option) || requestedWill(option)) {
             return;
         }
         setWantWill(option);
         ++doResponse[option];
         sendWill(option);
     }
 
     /* TERMINAL-TYPE option (end) */
 
     /**
      * Requests a {@code WONT}.
      *
      * @param option   Option code.
      * @throws IOException - Exception in I/O.
      **/
     final synchronized void requestWont(final int option) throws IOException {
         if (willResponse[option] == 0 && stateIsWont(option) || requestedWont(option)) {
             return;
         }
         setWantWont(option);
         ++doResponse[option];
         sendWont(option);
     }
 
     /**
      * Sends a byte.
      *
      * @param b   byte to send
      * @throws IOException - Exception in I/O.
      **/
     final synchronized void sendByte(final int b) throws IOException {
         _output_.write(b);
 
         /* Code Section added for supporting spystreams (start) */
         spyWrite(b);
         /* Code Section added for supporting spystreams (end) */
 
     }
 
     /**
      * Sends a {@code DO}.
      *
      * @param option   Option code.
      * @throws IOException - Exception in I/O.
      **/
     final synchronized void sendDo(final int option) throws IOException {
         if (debug || debugoptions) {
             System.err.println("DO: " + TelnetOption.getOption(option));
         }
         _output_.write(COMMAND_DO);
         _output_.write(option);
 
         /* Code Section added for sending the negotiation ASAP (start) */
         _output_.flush();
         /* Code Section added for sending the negotiation ASAP (end) */
     }
 
     /**
      * Sends a {@code DONT}.
      *
      * @param option   Option code.
      * @throws IOException - Exception in I/O.
      **/
     final synchronized void sendDont(final int option) throws IOException {
         if (debug || debugoptions) {
             System.err.println("DONT: " + TelnetOption.getOption(option));
         }
         _output_.write(COMMAND_DONT);
         _output_.write(option);
 
         /* Code Section added for sending the negotiation ASAP (start) */
         _output_.flush();
         /* Code Section added for sending the negotiation ASAP (end) */
     }
 
     /**
      * Sends terminal type information.
      *
      * @throws IOException - Exception in I/O.
      */
     final synchronized void sendTerminalType() throws IOException {
         if (debug) {
             System.err.println("SEND TERMINAL-TYPE: " + terminalType);
         }
         if (terminalType != null) {
             _output_.write(COMMAND_SB);
             _output_.write(COMMAND_IS);
             _output_.write(terminalType.getBytes(getCharset()));
             _output_.write(COMMAND_SE);
             _output_.flush();
         }
     }
 
     /**
      * Sends a {@code WILL}.
      *
      * @param option   Option code.
      * @throws IOException - Exception in I/O.
      **/
     final synchronized void sendWill(final int option) throws IOException {
         if (debug || debugoptions) {
             System.err.println("WILL: " + TelnetOption.getOption(option));
         }
         _output_.write(COMMAND_WILL);
         _output_.write(option);
 
         /* Code Section added for sending the negotiation ASAP (start) */
         _output_.flush();
         /* Code Section added for sending the negotiation ASAP (end) */
     }
 
     /**
      * Sends a {@code WONT}.
      *
      * @param option   Option code.
      * @throws IOException - Exception in I/O.
      **/
     final synchronized void sendWont(final int option) throws IOException {
         if (debug || debugoptions) {
             System.err.println("WONT: " + TelnetOption.getOption(option));
         }
         _output_.write(COMMAND_WONT);
         _output_.write(option);
 
         /* Code Section added for sending the negotiation ASAP (start) */
         _output_.flush();
         /* Code Section added for sending the negotiation ASAP (end) */
     }
 
     /**
      * Sets the state of the option.
      *
      * @param option   option code to be set.
      * @throws IOException
      */
     void setDo(final int option) throws IOException {
         options[option] |= DO_MASK;
 
         /* open TelnetOptionHandler functionality (start) */
         if (requestedDo(option) && optionHandlers[option] != null) {
             optionHandlers[option].setDo(true);
 
             final int[] subneg = optionHandlers[option].startSubnegotiationRemote();
 
             if (subneg != null) {
                 _sendSubnegotiation(subneg);
             }
         }
         /* open TelnetOptionHandler functionality (end) */
     }
 
     /**
      * Sets the state of the option.
      *
      * @param option   option code to be set.
      */
     void setDont(final int option) {
         options[option] &= ~DO_MASK;
 
         /* open TelnetOptionHandler functionality (start) */
         if (optionHandlers[option] != null) {
             optionHandlers[option].setDo(false);
         }
         /* open TelnetOptionHandler functionality (end) */
     }
 
     /**
      * Sets the state of the option.
      *
      * @param option   option code to be set.
      */
     void setWantDo(final int option) {
         options[option] |= REQUESTED_DO_MASK;
     }
 
     /**
      * Sets the state of the option.
      *
      * @param option   option code to be set.
      */
     void setWantDont(final int option) {
         options[option] &= ~REQUESTED_DO_MASK;
     }
 
     /**
      * Sets the state of the option.
      *
      * @param option   option code to be set.
      */
     void setWantWill(final int option) {
         options[option] |= REQUESTED_WILL_MASK;
     }
 
     /**
      * Sets the state of the option.
      *
      * @param option   option code to be set.
      */
     void setWantWont(final int option) {
         options[option] &= ~REQUESTED_WILL_MASK;
     }
 
     /**
      * Sets the state of the option.
      *
      * @param option   option code to be set.
      * @throws IOException
      */
     void setWill(final int option) throws IOException {
         options[option] |= WILL_MASK;
 
         /* open TelnetOptionHandler functionality (start) */
         if (requestedWill(option) && optionHandlers[option] != null) {
             optionHandlers[option].setWill(true);
 
             final int[] subneg = optionHandlers[option].startSubnegotiationLocal();
 
             if (subneg != null) {
                 _sendSubnegotiation(subneg);
             }
         }
         /* open TelnetOptionHandler functionality (end) */
     }
 
     /* open TelnetOptionHandler functionality (start) */
 
     /**
      * Sets the state of the option.
      *
      * @param option   option code to be set.
      */
     void setWont(final int option) {
         options[option] &= ~WILL_MASK;
 
         /* open TelnetOptionHandler functionality (start) */
         if (optionHandlers[option] != null) {
             optionHandlers[option].setWill(false);
         }
         /* open TelnetOptionHandler functionality (end) */
     }
 
     /**
      * Sends a read char on the spy stream.
      *
      * @param ch   character read from the session
      */
     void spyRead(final int ch) {
         final OutputStream spy = spyStream;
         if (spy != null) {
             try {
                 // never write '\r' on its own
                 if (ch != '\r') {
                     if (ch == '\n') {
                         spy.write('\r'); // add '\r' before '\n'
                     }
                     spy.write(ch); // write original character
                     spy.flush();
                 }
             } catch (final IOException e) {
                 spyStream = null;
             }
         }
     }
 
     /**
      * Sends a written char on the spy stream.
      *
      * @param ch   character written to the session
      */
     void spyWrite(final int ch) {
         if (!(stateIsDo(TelnetOption.ECHO) && requestedDo(TelnetOption.ECHO))) {
             final OutputStream spy = spyStream;
             if (spy != null) {
                 try {
                     spy.write(ch);
                     spy.flush();
                 } catch (final IOException e) {
                     spyStream = null;
                 }
             }
         }
     }
     /* Code Section added for supporting spystreams (end) */
 
     /**
      * Looks for the state of the option.
      *
      * @return true if a {@code DO} has been acknowledged.
      * @param option   option code to be looked up.
      */
     boolean stateIsDo(final int option) {
         return (options[option] & DO_MASK) != 0;
     }
 
     /**
      * Looks for the state of the option.
      *
      * @return true if a {@code DONT} has been acknowledged
      * @param option   option code to be looked up.
      */
     boolean stateIsDont(final int option) {
         return !stateIsDo(option);
     }
 
     /**
      * Looks for the state of the option.
      *
      * @return true if a {@code WILL} has been acknowledged
      * @param option   option code to be looked up.
      */
     boolean stateIsWill(final int option) {
         return (options[option] & WILL_MASK) != 0;
     }
 
     /**
      * Looks for the state of the option.
      *
      * @return true if a {@code WONT} has been acknowledged
      * @param option   option code to be looked up.
      */
     boolean stateIsWont(final int option) {
         return !stateIsWill(option);
     }
 
     /**
      * Unregisters the current notification handler.
      */
     public void unregisterNotifHandler() {
         notifhand = null;
     }
 }