Class ClientServer.ClientServerThread.TelnetInputReader

java.lang.Object
  ClientServer.ClientServerThread.TelnetInputReader

Enclosing class:

ClientServer.ClientServerThread

public class ClientServer.ClientServerThread.TelnetInputReader

extends Object

This class handles the input gathering and processing functions as well as the required echoing.

In order to be able to hide the users password when they enter it to log in, the telnet client must be set up to not locally echo anything. This is done by ClientServer.negotiate(). Since the client is not echoing, we must do the echoing.

Currently, the class properly handles carriage returns and backspaces, and ignores line-feeds and arrow keys.

Telnet protocol specifies that a newline is defined as a CR LF sequence, regardless of platform. The class catches the first CR, ignores any subsequent line feeds and calls TelnetPrintWriter.println(), whose purpose is to output CR LF sequences alongside the responsibilities of PrintWriter.

Author:

Kevin Thompson [antiduh@csh.rit.edu]

Field Summary

static int	A_BS
static int	A_CR
static int	A_DEL
static int	A_ESC
static int	A_LF
static int	A_NAK
static int	A_NUL
static int	A_SP
private BufferedInputStream	in
private PrintWriter	out
static int	T_IAC

Constructor Summary

ClientServer.ClientServerThread.TelnetInputReader(BufferedInputStream _in, PrintWriter _out)
Constructs the TelnetInputReader.

Method Summary

String	intDump(String input) Takes the given string input and converts it to a decimal string in the form 100:100:90:80 so that unprinted characters will be 'visible'
int	read(boolean echo) Reads a single character from the input BufferedInputStream.
String	readLine(boolean echo) Reads a line of text using the read() method defined above.

Methods inherited from class java.lang.Object

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

Field Detail

A_BS

public static final int A_BS

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Constant Field Values

A_LF

public static final int A_LF

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Constant Field Values

A_CR

public static final int A_CR

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Constant Field Values

A_NAK

public static final int A_NAK

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Constant Field Values

A_ESC

public static final int A_ESC

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Constant Field Values

A_SP

public static final int A_SP

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Constant Field Values

A_DEL

public static final int A_DEL

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Constant Field Values

A_NUL

public static final int A_NUL

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Constant Field Values

T_IAC

public static final int T_IAC

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Constant Field Values

in

private BufferedInputStream in

out

private PrintWriter out

Constructor Detail

ClientServer.ClientServerThread.TelnetInputReader

public ClientServer.ClientServerThread.TelnetInputReader(BufferedInputStream _in,
                                                         PrintWriter _out)

Constructs the TelnetInputReader. It just saves the arguments.

Parameters:

_in - The BufferedInputStream to read from.

_out - The printwriter to echo to

Method Detail

read

public int read(boolean echo)
         throws IOException

Reads a single character from the input BufferedInputStream.

Handles: CR, Backspace

Ignores: LF, Arrow keys

This discards all arrow keys and linefeeds. CR's are sent back to readLine(). CR's, LF's, arrows, and backspaces are not directly sent back to the client. Those are handled in readLine().

After each read(), the result must be checked. If its -1, the user disconnected and we need to throw the IOException to the rest of the program.

All single character writes need to be flushed through the buffer so that the chars appear immediately after the user types them.

Parameters:

echo - If true, 'normal' unhandled chars are sent back through the class's PrintWriter

Returns:

The integer of the character.

Throws:

IOException

readLine

public String readLine(boolean echo)
                throws IOException

Reads a line of text using the read() method defined above. Carriage returns, and linefeeds are not echoed back, instead println() is called. Backspaces delete text from the buffer, and are sent to the telnet client in the sequence 8,32,8 to whiteout the text in the previous position. If the client does not enter any text and instead just hits return, then a zero-length string "" is returned.

Parameters:

echo - Whether or not to echo unhandled characters.

Returns:

The line of text.

Throws:

IOException

intDump

public String intDump(String input)

Takes the given string input and converts it to a decimal string in the form 100:100:90:80 so that unprinted characters will be 'visible'

Parameters:

input - The input to convert to a a decimal string