ipworks
Class Telnet

java.lang.Object
  |
  +--ipworks.Telnet

public class Telnet

extends java.lang.Object

The Telnet bean is used to communicate with servers implementing the TELNET protocol.

The Telnet bean provides a simple interface to Telnet communications as specified by RFC 854. It allows sending of Telnet command codes to remote Telnet servers and it scans the input data for Telnet commands. Appropriate events are fired for received commands.

The connection interface is very similar to that of IPPort. The same properties and events are used for sending and receiving normal data, and the same property set is used for setting properties of the connection. The Telnet bean adds a number of properties like Command , DoOption , etc. which allow sending of Telnet commands to the other end. The respective events ( Command , Do , etc.) are fired when the corresponding Telnet commands are received.

Constructor Summary

Telnet()

Method Summary

void	addTelnetEventListener(ipworks.TelnetEventListener l)
java.lang.String	config(java.lang.String configurationString) Sets or retrieves a beanconfiguration setting.
void	connect(java.lang.String host) Connect to a remote host.
void	disconnect() Disconnect from the remote host.
void	doEvents() Processes events from the internal message queue.
int	getBytesSent() The number of bytes actually sent after an assignment to DataToSend .
ipworks.Firewall	getFirewall() A set of properties related to firewall access.
java.lang.String	getLocalHost() The name of the local host or user-assigned IP interface through which connections are initiated or accepted.
int	getLocalPort() The TCP port in the local host where IPPort binds.
java.lang.String	getRemoteHost() The address of the remote host.
int	getRemotePort() The Telnet port in the remote host (default is 23).
int	getTimeout() A timeout for the bean.
boolean	isAcceptData() Enables or disables data reception (the DataIn event).
boolean	isConnected() Triggers a connection or disconnection.
boolean	isKeepAlive() When True, KEEPALIVE packets are enabled (for long connections).
boolean	isLinger() When set to True, connections are terminated gracefully.
boolean	isTransparent() When True, Telnet command processing is disabled.
void	removeTelnetEventListener(ipworks.TelnetEventListener l)
void	send(byte[] text) Send data to the remote host.
void	setAcceptData(boolean acceptData) Enables or disables data reception (the DataIn event).
void	setCommand(int command) A single character Telnet command code to be sent to the server.
void	setConnected(boolean connected) Triggers a connection or disconnection.
void	setDataToSend(byte[] dataToSend) A string of data to be sent to the remote host.
void	setDontOption(int dontOption) A single character Telnet option code to be sent to the server with the Telnet DONT command.
void	setDoOption(int doOption) A single character Telnet option code to be sent to the server with the Telnet DO command.
void	setDoSubOption(byte[] doSubOption) A Telnet suboption to send to the server with the suboption command.
void	setFirewall(ipworks.Firewall firewall) A set of properties related to firewall access.
void	setKeepAlive(boolean keepAlive) When True, KEEPALIVE packets are enabled (for long connections).
void	setLinger(boolean linger) When set to True, connections are terminated gracefully.
void	setLocalHost(java.lang.String localHost) The name of the local host or user-assigned IP interface through which connections are initiated or accepted.
void	setLocalPort(int localPort) The TCP port in the local host where IPPort binds.
void	setRemoteHost(java.lang.String remoteHost) The address of the remote host.
void	setRemotePort(int remotePort) The Telnet port in the remote host (default is 23).
void	setTimeout(int timeout) A timeout for the bean.
void	setTransparent(boolean transparent) When True, Telnet command processing is disabled.
void	setUrgentData(byte[] urgentData) A string of data to be sent urgently (out-of-band) to the remote host.
void	setWillOption(int willOption) A single character Telnet option code to be sent to the server with the Telnet WILL command.
void	setWontOption(int wontOption) A single character Telnet option code to be sent to the server with the Telnet WONT command.

Methods inherited from class java.lang.Object

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

Constructor Detail

Telnet

public Telnet()

Method Detail

isAcceptData

public boolean isAcceptData()

Enables or disables data reception (the DataIn event).

Setting the property to False, temporarily disables data reception (and the DataIn event). Setting the property to True, re-enables data reception.

setAcceptData

public void setAcceptData(boolean acceptData)
                   throws IPWorksException

Enables or disables data reception (the DataIn event).

Setting the property to False, temporarily disables data reception (and the DataIn event). Setting the property to True, re-enables data reception.

IPWorksException

getBytesSent

public int getBytesSent()

The number of bytes actually sent after an assignment to DataToSend .

The BytesSent property shows how many bytes were sent after the last assignment to DataToSend or UrgentData . Please check the DataToSend property for more information.

setCommand

public void setCommand(int command)
                throws IPWorksException

A single character Telnet command code to be sent to the server.

Codes for Telnet commands and their meanings are defined in the Telnet RFCs. Here are some examples:

241 (NOP)

No operation.

242 (Data Mark)

The data stream portion of a Synch. This should always be accompanied by a TCP Urgent notification.

243 (Break)

NVT character BRK.

244 (Interrupt Process)

The function IP.

245 (Abort Output)

The function AO.

246 (Are You There)

The function AYT.

247 (Erase Character)

The function EC.

248 (Erase Line)

The function EL.

249 (Go Ahead)

The GA signal.

IPWorksException

isConnected

public boolean isConnected()

Triggers a connection or disconnection.

Setting the Connected property to True makes the bean attempt to connect to the host identified by the RemoteHost property. If successful, after the connection is achieved, the value of the property changes to True and the Connected event is fired.

Setting Connected to False closes the connection. How and when the connection is closed is controlled by the Linger property.

setConnected

public void setConnected(boolean connected)
                  throws IPWorksException

Triggers a connection or disconnection.

Setting the Connected property to True makes the bean attempt to connect to the host identified by the RemoteHost property. If successful, after the connection is achieved, the value of the property changes to True and the Connected event is fired.

Setting Connected to False closes the connection. How and when the connection is closed is controlled by the Linger property.

IPWorksException

setDataToSend

public void setDataToSend(byte[] dataToSend)
                   throws IPWorksException

A string of data to be sent to the remote host.

Assigning a string to the DataToSend property makes the bean send the string to the remote host. The Send method provides similar functionality.

If you are sending data to the remote host faster than it can process it, or faster than the network's bandwidth allows, the outgoing queue might fill up. When this happens, DataToSend fails with exception 10035: "[10035] Operation would block" (WSAEWOULDBLOCK). You can check this error, and then try to send the data again. The BytesSent property shows how many bytes were sent (if any). If 0 bytes were sent, then you can wait for the ReadyToSend event before attempting to send data again. (However, please note that ReadyToSend is not fired when part of the data is successfully sent).

IPWorksException

setDontOption

public void setDontOption(int dontOption)
                   throws IPWorksException

A single character Telnet option code to be sent to the server with the Telnet DONT command.

For a list of option codes and their descriptions, please look at the Telnet RFCs. The following are a few examples:

0 (TRANSMIT-BINARY)

Enables or disables binary (8 bit) transmission.

1 (ECHO)

Telnet ECHO option. Specifies whether bytes sent should be echoed or not.

3 (SUPPRESS-GO-AHEAD)

Used to enable or disable transmission of the Telnet GO_AHEAD command.

24 (TERMINAL-TYPE)

Allows or disallows terminal type negotiation.

31 (NAWS)

Allows or disallows window size negotiation.

IPWorksException

setDoOption

public void setDoOption(int doOption)
                 throws IPWorksException

A single character Telnet option code to be sent to the server with the Telnet DO command.

For a list of option codes and their descriptions, please look at the Telnet RFCs. The following are a few examples:

0 (TRANSMIT-BINARY)

Enables or disables binary (8 bit) transmission.

1 (ECHO)

Telnet ECHO option. Specifies whether bytes sent should be echoed or not.

3 (SUPPRESS-GO-AHEAD)

Used to enable or disable transmission of the Telnet GO_AHEAD command.

24 (TERMINAL-TYPE)

Allows or disallows terminal type negotiation.

31 (NAWS)

Allows or disallows window size negotiation.

IPWorksException

setDoSubOption

public void setDoSubOption(byte[] doSubOption)
                    throws IPWorksException

A Telnet suboption to send to the server with the suboption command.

For a list of valid Telnet suboptions and their descriptions please look at the Telnet RFCs.

You don't need to specify the suboption start and suboption end codes. Those are appended automatically by the bean. For example, to send a terminal type suboption to request setting the terminal type to 'vt100', you must send ASCII 24, followed by ASCII 0, followed by "vt100" (without the quotes).

IPWorksException

getFirewall

public ipworks.Firewall getFirewall()

A set of properties related to firewall access.

This is a FIREWALL type property which contains fields describing the firewall through which the bean will attempt to connect.

setFirewall

public void setFirewall(ipworks.Firewall firewall)
                 throws IPWorksException

A set of properties related to firewall access.

This is a FIREWALL type property which contains fields describing the firewall through which the bean will attempt to connect.

IPWorksException

isKeepAlive

public boolean isKeepAlive()

When True, KEEPALIVE packets are enabled (for long connections).

The KeepAlive enables the SO_KEEPALIVE option on the socket. This option prevents long connections from timing out in case of inactivity.

Please note that system TCP/IP stack implementations are not required to support SO_KEEPALIVE.

setKeepAlive

public void setKeepAlive(boolean keepAlive)
                  throws IPWorksException

When True, KEEPALIVE packets are enabled (for long connections).

The KeepAlive enables the SO_KEEPALIVE option on the socket. This option prevents long connections from timing out in case of inactivity.

Please note that system TCP/IP stack implementations are not required to support SO_KEEPALIVE.

IPWorksException

isLinger

public boolean isLinger()

When set to True, connections are terminated gracefully.

The Linger property controls how a connection is closed. The default is True. In this case the connection is closed only after all the data is sent. Setting it to False forces an abrupt (hard) disconnection. Any data that were in the sending queue may be lost.

The default behavior (which is also the default mode for some Winsock stream sockets) might result in an indefinite delay in closing the connection. Although the bean returns control immediately, the system might indefinitely hold system resources until all pending data are sent (even after your application closes). This means that valuable system resources might be wasted.

Setting Linger to False forces an immediate disconnection. If you know that the other side has received all the data you had sent (by a client acknowledgment, for example), setting Linger to False might be the appropriate course of action.

setLinger

public void setLinger(boolean linger)
               throws IPWorksException

When set to True, connections are terminated gracefully.

The Linger property controls how a connection is closed. The default is True. In this case the connection is closed only after all the data is sent. Setting it to False forces an abrupt (hard) disconnection. Any data that were in the sending queue may be lost.

The default behavior (which is also the default mode for some Winsock stream sockets) might result in an indefinite delay in closing the connection. Although the bean returns control immediately, the system might indefinitely hold system resources until all pending data are sent (even after your application closes). This means that valuable system resources might be wasted.

Setting Linger to False forces an immediate disconnection. If you know that the other side has received all the data you had sent (by a client acknowledgment, for example), setting Linger to False might be the appropriate course of action.

IPWorksException

getLocalHost

public java.lang.String getLocalHost()

The name of the local host or user-assigned IP interface through which connections are initiated or accepted.

The LocalHost property contains the name of the local host as obtained by the gethostname() system call, or if the user has assigned an IP address, the value of that address.

In multihomed hosts (machines with more than one IP interface) setting LocalHost to the value of an interface will make the bean initiate connections (or accept in the case of server beans) only through that interface.

If the bean is connected, the LocalHost property shows the IP address of the interface through which the connection is made in internet dotted format (aaa.bbb.ccc.ddd). In most cases, this is the address of the local host, except for multihomed hosts (machines with more than one IP interface).

NOTE: LocalHost is not persistent. You must always set it in code, and never in the property window.

setLocalHost

public void setLocalHost(java.lang.String localHost)
                  throws IPWorksException

The name of the local host or user-assigned IP interface through which connections are initiated or accepted.

The LocalHost property contains the name of the local host as obtained by the gethostname() system call, or if the user has assigned an IP address, the value of that address.

In multihomed hosts (machines with more than one IP interface) setting LocalHost to the value of an interface will make the bean initiate connections (or accept in the case of server beans) only through that interface.

If the bean is connected, the LocalHost property shows the IP address of the interface through which the connection is made in internet dotted format (aaa.bbb.ccc.ddd). In most cases, this is the address of the local host, except for multihomed hosts (machines with more than one IP interface).

NOTE: LocalHost is not persistent. You must always set it in code, and never in the property window.

IPWorksException

getLocalPort

public int getLocalPort()

The TCP port in the local host where IPPort binds.

The LocalPort property must be set before a connection is attempted. It instructs the bean to bind to a specific port (or communication endpoint) in the local machine.

Setting it to 0 (default) enables the TCP/IP stack to choose a port at random. The chosen port will be shown by the LocalPort property after the connection is established.

LocalPort cannot be changed once a connection is made. Any attempt to set the LocalPort property when a connection is active will generate an error.

The LocalPort property is useful when trying to connect to services that require a trusted port in the client side.

setLocalPort

public void setLocalPort(int localPort)
                  throws IPWorksException

The TCP port in the local host where IPPort binds.

The LocalPort property must be set before a connection is attempted. It instructs the bean to bind to a specific port (or communication endpoint) in the local machine.

Setting it to 0 (default) enables the TCP/IP stack to choose a port at random. The chosen port will be shown by the LocalPort property after the connection is established.

LocalPort cannot be changed once a connection is made. Any attempt to set the LocalPort property when a connection is active will generate an error.

The LocalPort property is useful when trying to connect to services that require a trusted port in the client side.

IPWorksException

getRemoteHost

public java.lang.String getRemoteHost()

The address of the remote host. Domain names are resolved to IP addresses.

The RemoteHost property specifies the IP address (IP number in dotted internet format) or Domain Name of the remote host. It is set before a connection is attempted and cannot be changed once a connection is established.

If the RemoteHost property is set to a Domain Name, a DNS request is initiated, and upon successful termination of the request, the RemoteHost property is set to the corresponding address. If the search is not successful, an error is returned.

If the bean is configured to use a SOCKS firewall, the value assigned to this property may be preceeded with a "*". If this is the case, the host name is passed to the firewall unresolved and the firewall performs the DNS resolution.

Example (Connecting)

 IPPortControl.RemoteHost = "MyHostNameOrIP"
 IPPortControl.RemotePort = 777
 IPPortControl.Connected = true 

setRemoteHost

public void setRemoteHost(java.lang.String remoteHost)
                   throws IPWorksException

The address of the remote host. Domain names are resolved to IP addresses.

The RemoteHost property specifies the IP address (IP number in dotted internet format) or Domain Name of the remote host. It is set before a connection is attempted and cannot be changed once a connection is established.

If the RemoteHost property is set to a Domain Name, a DNS request is initiated, and upon successful termination of the request, the RemoteHost property is set to the corresponding address. If the search is not successful, an error is returned.

If the bean is configured to use a SOCKS firewall, the value assigned to this property may be preceeded with a "*". If this is the case, the host name is passed to the firewall unresolved and the firewall performs the DNS resolution.

Example (Connecting)

 IPPortControl.RemoteHost = "MyHostNameOrIP"
 IPPortControl.RemotePort = 777
 IPPortControl.Connected = true 

IPWorksException

getRemotePort

public int getRemotePort()

The Telnet port in the remote host (default is 23).

A valid port number (a value between 1 and 65535) is required for the connection to take place. The property must be set before a connection is attempted and cannot be changed once a connection is established. Any attempt to change this property while connected will fail with an error.

setRemotePort

public void setRemotePort(int remotePort)
                   throws IPWorksException

The Telnet port in the remote host (default is 23).

A valid port number (a value between 1 and 65535) is required for the connection to take place. The property must be set before a connection is attempted and cannot be changed once a connection is established. Any attempt to change this property while connected will fail with an error.

IPWorksException

getTimeout

public int getTimeout()

A timeout for the bean.

If the Timeout property is set to 0, all operations return immediately, potentially failing with an 'WOULDBLOCK' error if data can't be sent or received immediately.

If Timeout is set to a positive value, the bean will automatically retry each operation that would otherwise result in a 'WOULDBLOCK' error for a maximum of Timeout seconds.

The bean will use DoEvents to enter an efficient wait loop during any potential waiting period, making sure that all system events are processed immediately as they arrive. This ensures that the host application does not "freeze" and remains responsive.

If Timeout expires, and the operation is not yet complete, the bean throws an IPWorksException raises an IPWorksException exception .

Please note that by default, all timeouts are inactivity timeouts , i.e. the timeout period is extended by Timeout seconds when data is successfully sent or received.

Optionally, the behaviour of the bean may be changed to absolute timeouts , i.e. the bean will wait for a maximum of Timeout seconds since the beginning of the operation, without extending the timeout period during communications.

This behavior is controlled by theAbsoluteTimeoutconfiguration setting.

The default value for the Timeout property is 0 (asynchronous operation).

setTimeout

public void setTimeout(int timeout)
                throws IPWorksException

A timeout for the bean.

If the Timeout property is set to 0, all operations return immediately, potentially failing with an 'WOULDBLOCK' error if data can't be sent or received immediately.

If Timeout is set to a positive value, the bean will automatically retry each operation that would otherwise result in a 'WOULDBLOCK' error for a maximum of Timeout seconds.

The bean will use DoEvents to enter an efficient wait loop during any potential waiting period, making sure that all system events are processed immediately as they arrive. This ensures that the host application does not "freeze" and remains responsive.

If Timeout expires, and the operation is not yet complete, the bean throws an IPWorksException raises an IPWorksException exception .

Please note that by default, all timeouts are inactivity timeouts , i.e. the timeout period is extended by Timeout seconds when data is successfully sent or received.

Optionally, the behaviour of the bean may be changed to absolute timeouts , i.e. the bean will wait for a maximum of Timeout seconds since the beginning of the operation, without extending the timeout period during communications.

This behavior is controlled by theAbsoluteTimeoutconfiguration setting.

The default value for the Timeout property is 0 (asynchronous operation).

IPWorksException

isTransparent

public boolean isTransparent()

When True, Telnet command processing is disabled.

The Transparent property allows you to enable or disable Telnet command processing. When command processing is disabled, any data received is provided with no modifications.

setTransparent

public void setTransparent(boolean transparent)
                    throws IPWorksException

When True, Telnet command processing is disabled.

The Transparent property allows you to enable or disable Telnet command processing. When command processing is disabled, any data received is provided with no modifications.

IPWorksException

setUrgentData

public void setUrgentData(byte[] urgentData)
                   throws IPWorksException

A string of data to be sent urgently (out-of-band) to the remote host.

The UrgentData property behaves exactly like the DataToSend property except that the data is sent Out Of Band (urgent). This means that the data assigned to UrgentData will bypass the normal TCP queuing mechanism. Use this property with caution.

IPWorksException

setWillOption

public void setWillOption(int willOption)
                   throws IPWorksException

A single character Telnet option code to be sent to the server with the Telnet WILL command.

For a list of option codes and their descriptions, please look at the Telnet RFCs. The following are a few examples:

0 (TRANSMIT-BINARY)

Enables or disables binary (8 bit) transmission.

1 (ECHO)

Telnet ECHO option. Specifies whether bytes sent should be echoed or not.

3 (SUPPRESS-GO-AHEAD)

Used to enable or disable transmission of the Telnet GO_AHEAD command.

24 (TERMINAL-TYPE)

Allows or disallows terminal type negotiation.

31 (NAWS)

Allows or disallows window size negotiation.

IPWorksException

setWontOption

public void setWontOption(int wontOption)
                   throws IPWorksException

A single character Telnet option code to be sent to the server with the Telnet WONT command.

For a list of option codes and their descriptions, please look at the Telnet RFCs. The following are a few examples:

0 (TRANSMIT-BINARY)

Enables or disables binary (8 bit) transmission.

1 (ECHO)

Telnet ECHO option. Specifies whether bytes sent should be echoed or not.

3 (SUPPRESS-GO-AHEAD)

Used to enable or disable transmission of the Telnet GO_AHEAD command.

24 (TERMINAL-TYPE)

Allows or disallows terminal type negotiation.

31 (NAWS)

Allows or disallows window size negotiation.

IPWorksException

config

public java.lang.String config(java.lang.String configurationString)
                        throws IPWorksException

Sets or retrieves a beanconfiguration setting.

Config is a generic method available in every bean. It is used to set and retrieveconfiguration settingsfor the bean.

Configuration settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the bean, access to these internal properties is provided through the Config method.

To set a configuration setting named PROPERTY , you must call Config("PROPERTY=VALUE") , where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a configuration setting, you must call Config("PROPERTY") . The value will be returned as a string.

IPWorksException

connect

public void connect(java.lang.String host)
             throws IPWorksException

Connect to a remote host.

Calling this method is equivalent to setting the RemoteHost property to Host and then setting the Connected property to True.

IPWorksException

disconnect

public void disconnect()
                throws IPWorksException

Disconnect from the remote host.

Calling this method is equivalent to setting the Connected property to False.

IPWorksException

doEvents

public void doEvents()
              throws IPWorksException

Processes events from the internal message queue.

When DoEvents is called, the bean processes any available events. If no events are available, it waits for a preset period of time, and then returns.

IPWorksException

send

public void send(byte[] text)
          throws IPWorksException

Send data to the remote host.

Calling this method is equivalent to setting the DataToSend property to Text .

IPWorksException

addTelnetEventListener

public void addTelnetEventListener(ipworks.TelnetEventListener l)
                            throws java.util.TooManyListenersException

java.util.TooManyListenersException

removeTelnetEventListener

public void removeTelnetEventListener(ipworks.TelnetEventListener l)