Channel (Maverick Legacy - Server Assembly 1.7.61 API)

java.lang.Object
- com.maverick.sshd.Channel

Direct Known Subclasses:

AgentForwardingChannel, ForwardingChannel, SessionChannel
```
public abstract class Channel
extends Object
```
This abstract class provides the basic functions of an SSH2 channel. All terminal sessions, forwarded connections etc, are channels. Either side may open a channel and multiple channels are multiplexed into a single connection. Channels are flow-controlled so that no data may be sent to a channel until a message is received to indicate that a window space is available.

Channel implementations are identified by name and to support the opening of a channel your server should add the channel's unique name to the com.maverick.sshd.ConfigurationContext#supportedChannels(). This can be completed in your com.maverick.sshd.SshDaemon#configure(ConfigurationContext) method.
```
 protected void configure(ConfigurationContext context) {
        context.supportedChannels().add("chat@sshtools.com",
                        Class.forName("com.sshtools.ChatChannel"));
 }
 
```
Data sent by the channel is buffered and sent when window space is available on the remote side. The incoming window space is decremented whenever data is received with the abstract evaluateWindowSpace(int) method being called to enable the channel implementation to add further window space should it require.
Author:

Lee David Painter

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

protected class Channel.DataBlock

protected class Channel.QueuedData

Nested Classes
Modifier and Type	Class and Description
`protected class`	`Channel.DataBlock`
`protected class`	`Channel.QueuedData`

Field Summary

Fields
Modifier and Type	Field and Description
`protected ConnectionProtocol`	`connection` The Connection Protocol instance managing this session, use this instance to disconnect the session or obtain the ip address of the remote client.
`protected int`	`localwindow`
`protected Object`	`localWindowLock`

Constructor Summary

Constructors
Constructor and Description

Channel(String channelType, int maximumPacketSize, int initialWindowSize)
Construct a channel with the specified settings.

Constructors
Constructor and Description
`Channel(String channelType, int maximumPacketSize, int initialWindowSize)` Construct a channel with the specified settings.

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`addEventListener(ChannelEventListener listener)` Enable other objects to receive channel events
`void`	`addInputListener(OutputStream out)` Add an OutputStream to receive all channel data input from the remote side of the connection.
`void`	`addOutputListener(OutputStream out)` Add an OutputStream to receive all of the channels output.
`protected boolean`	`canClose()` Can this channel close?
`void`	`clearIdleState(IdleStateListener listener)` Clear an idle state listener.
`void`	`close()`
`protected void`	`close(boolean forceClose)` This method closes the channel and free's its resources.
`protected void`	`consumeWindowSpace(int length)`
`protected abstract byte[]`	`createChannel()` Called when the channel is being created.
`protected ConnectionAwareTask`	`createCloseTask(boolean forceClose)`
`protected abstract void`	`evaluateWindowSpace(int remaining)` Called to evaluate the window space available.
`protected void`	`executeTask(ConnectionAwareTask task)`
`String`	`getChannelType()` The name of this channel.
`ConnectionProtocol`	`getConnection()` Returns the `ConnectionProtocol` associated with this channel.
`SshContext`	`getContext()` Get the current configuration from the underlying connection.
`int`	`getLocalId()` The local channel id
`int`	`getLocalPacket()` The maximum size of a single packet that the local side will accept.
`int`	`getLocalWindow()` The current size of the local data window.
`int`	`getQueueSize()`
`int`	`getRemoteId()` The remote sides channel id
`int`	`getRemotePacket()` The maximum size of a single packet that the remote side will accept.
`int`	`getRemoteWindow()` The current size of the remote data window.
`String`	`getSessionIdentifier()` Get the session id for the current connection.
`boolean`	`isClosed()` Indicates the channel has been closed
`boolean`	`isClosing()` Indicates whether the channel is currently performing a close operation
`boolean`	`isEOF()` Indicates that the channel is EOF (it will not be receiving any more data from the remote side).
`protected boolean`	`isOpen()` Get the open state of the channel.
`protected boolean`	`isSelfManagedWindowSpace()`
`protected void`	`markEOF()`
`protected abstract void`	`onChannelClosed()` Called when the channel has been closed to enable resources to be freed.
`protected abstract void`	`onChannelClosing()` Called before the channel is closed
`protected abstract void`	`onChannelData(byte[] data)` Called by the channel when data arrives from the remote side.
`protected abstract void`	`onChannelFree()` This method is called when the channel has been closed and all its resources are no longer required.
`protected abstract void`	`onChannelOpen()` Called when the channel has been opened - this method is only called when the remote side requests a channel open.
`protected abstract void`	`onChannelOpenConfirmation()` Called when the channel has been confirmed as open by the remote side - this method is only called when the channel has been requested by this side of the connection
`protected void`	`onChannelOpenFailure()` Called when the remote side fails to open a channel in response to our request.
`protected abstract void`	`onChannelRequest(String type, boolean wantreply, byte[] requestdata)` Called when a channel request is received.
`protected abstract void`	`onExtendedData(byte[] data, int type)` Called by the channel when extended data arrives
`protected abstract void`	`onLocalEOF()` Called when the local side is EOF.
`protected void`	`onRemoteClose()` Called when the remote side closes the channel.
`protected abstract void`	`onRemoteEOF()` Called when the remote side reports its OutputStream as EOF.
`protected void`	`onWindowAdjust(int count)`
`protected abstract byte[]`	`openChannel(byte[] requestdata)` Called when the channel is being opened.
`protected int`	`queueSize()`
`protected void`	`registerExtendedData(int type)` Call this method to register an extended data type.
`void`	`resetIdleState(IdleStateListener listener)` Allows a channel to register and receive idle state events.
`void`	`sendChannelData(byte[] data)` Send channel data to the remote side of the channel.
`void`	`sendChannelData(byte[] data, int off, int len)` Send channel data to the remote side of the channel.
`void`	`sendChannelData(byte[] data, int off, int len, Runnable r)`
`void`	`sendChannelData(byte[] data, Runnable r)`
`void`	`sendChannelDataAndBlock(byte[] data, int off, int len)`
`protected void`	`sendChannelRequest(String type, boolean wantreply, byte[] requestdata)` Send a channel request.
`protected void`	`sendEOF()` You can send EOF when you have no more data to send.
`protected void`	`sendExtendedData(byte[] data, int type)` Send extended channel data.
`protected void`	`sendExtendedData(byte[] data, int off, int len, int type)` Send extended channel data.
`protected void`	`sendRequestResponse(boolean succeeded)` Send a channel request.
`protected void`	`sendWindowAdjust(int count)` Adjust the local window by adding more bytes.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - connection
```
protected ConnectionProtocol connection
```
    The Connection Protocol instance managing this session, use this instance to disconnect the session or obtain the ip address of the remote client.
  - localwindow
```
protected int localwindow
```
  - localWindowLock
```
protected Object localWindowLock
```
- Constructor Detail
  - Channel
```
public Channel(String channelType,
               int maximumPacketSize,
               int initialWindowSize)
```
    Construct a channel with the specified settings.
    
    Parameters:
    
    channelType - the name of the channel, for example "session" or "tcpip-forward"
    
    maximumPacketSize - the maximum size of an individual packet that the remote side can send through the channel
    
    initialWindowSize - the initial size of the local window.
- Method Detail
  - isClosed
```
public boolean isClosed()
```
    Indicates the channel has been closed
    
    Returns:
    
    boolean
  - isEOF
```
public boolean isEOF()
```
    Indicates that the channel is EOF (it will not be receiving any more data from the remote side).
    
    Returns:
    
    boolean
  - getQueueSize
```
public int getQueueSize()
```
  - resetIdleState
```
public void resetIdleState(IdleStateListener listener)
```
    Allows a channel to register and receive idle state events. Call this method to reset the idle state of a channel (i.e when activity has occurred). The IdleStateListener instance passed as a parameter will receive notification once the channel reaches an idle state. NOTE: It is the callers responsibility to call clearIdleState method to ensure references are released.
    
    Parameters:
    
    listener - IdleStateListener
  - clearIdleState
```
public void clearIdleState(IdleStateListener listener)
```
    Clear an idle state listener.
    
    Parameters:
    
    listener -
  - addEventListener
```
public void addEventListener(ChannelEventListener listener)
```
    Enable other objects to receive channel events
    
    Parameters:
    
    listener -
  - addInputListener
```
public void addInputListener(OutputStream out)
```
    Add an OutputStream to receive all channel data input from the remote side of the connection.
    
    Parameters:
    
    out - OutputStream
  - addOutputListener
```
public void addOutputListener(OutputStream out)
```
    Add an OutputStream to receive all of the channels output.
    
    Parameters:
    
    out - OutputStream
  - getChannelType
```
public String getChannelType()
```
    The name of this channel.
    
    Returns:
    
    String
  - getRemoteWindow
```
public int getRemoteWindow()
```
    The current size of the remote data window.
    
    Returns:
    
    int
  - getLocalWindow
```
public int getLocalWindow()
```
    The current size of the local data window.
    
    Returns:
    
    int
  - getLocalPacket
```
public int getLocalPacket()
```
    The maximum size of a single packet that the local side will accept.
    
    Returns:
    
    int
  - getRemotePacket
```
public int getRemotePacket()
```
    The maximum size of a single packet that the remote side will accept.
    
    Returns:
    
    int
  - getLocalId
```
public int getLocalId()
```
    The local channel id
    
    Returns:
    
    int
  - getRemoteId
```
public int getRemoteId()
```
    The remote sides channel id
    
    Returns:
    
    int
  - queueSize
```
protected int queueSize()
```
  - registerExtendedData
```
protected void registerExtendedData(int type)
                             throws IOException
```
    Call this method to register an extended data type. This must be performed when using extended data so that the server can buffer data individually for each extended data type. It is recommended that extended data be registered when the channel is being created or opened.
    
    Parameters:
    
    type -
    
    Throws:
    
    IOException
  - getSessionIdentifier
```
public String getSessionIdentifier()
```
    Get the session id for the current connection.
    
    Returns:
    
    byte[]
  - onWindowAdjust
```
protected void onWindowAdjust(int count)
```
  - getConnection
```
public ConnectionProtocol getConnection()
```
    Returns the ConnectionProtocol associated with this channel.
    
    Returns:
    
    ConnectionProtocol
  - consumeWindowSpace
```
protected void consumeWindowSpace(int length)
```
  - isSelfManagedWindowSpace
```
protected boolean isSelfManagedWindowSpace()
```
  - sendChannelData
```
public void sendChannelData(byte[] data)
```
    Send channel data to the remote side of the channel. The byte array passed into this method will be sent asynchronously so ensure that no other class has access to this after this method returns, failing to do so may cause data corruption.
    
    Parameters:
    
    data -
  - sendChannelData
```
public void sendChannelData(byte[] data,
                            Runnable r)
```
  - sendChannelData
```
public void sendChannelData(byte[] data,
                            int off,
                            int len)
```
    Send channel data to the remote side of the channel. The byte array passed into this method will be sent asynchronously so ensure that no other class has access to this after this method returns, failing to do so may cause data corruption.
    
    Parameters:
    
    data -
    
    off -
    
    len -
  - sendChannelData
```
public void sendChannelData(byte[] data,
                            int off,
                            int len,
                            Runnable r)
```
  - sendChannelDataAndBlock
```
public void sendChannelDataAndBlock(byte[] data,
                                    int off,
                                    int len)
```
  - getContext
```
public SshContext getContext()
```
    Get the current configuration from the underlying connection.
    
    Returns:
    
    ConfigurationContext
  - sendExtendedData
```
protected void sendExtendedData(byte[] data,
                                int type)
```
    Send extended channel data. This data is sent as an extended 'type' which should be known by the channel at the remote side. For example within a session channel an extended data type is used to transfer stderr data from the server to the client.
    
    Parameters:
    
    data -
    
    type -
  - sendExtendedData
```
protected void sendExtendedData(byte[] data,
                                int off,
                                int len,
                                int type)
```
    Send extended channel data. This data is sent as an extended 'type' which should be known by the channel at the remote side. For example within a session channel an extended data type is used to transfer stderr data from the server to the client.
    
    Parameters:
    
    data -
    
    off -
    
    len -
    
    type -
  - onChannelData
```
protected abstract void onChannelData(byte[] data)
```
    Called by the channel when data arrives from the remote side.
    
    Parameters:
    
    data -
  - onExtendedData
```
protected abstract void onExtendedData(byte[] data,
                                       int type)
```
    Called by the channel when extended data arrives
    
    Parameters:
    
    data -
  - sendChannelRequest
```
protected void sendChannelRequest(String type,
                                  boolean wantreply,
                                  byte[] requestdata)
```
    Send a channel request. Many channel types have extensions that are specific to that particular channel type. An example is requresting a pty (pseudo terminal) for an interactive session. This method enables the sending of channel requests but does not support receiving responses. This should not present a problem as server implementations tend to send messages as one way information, for example the exit-status request of an interactive session.
    
    To handle requests from a client implement onChannelRequest(String,boolean,byte[]).
    
    Parameters:
    
    type -
    
    wantreply -
    
    requestdata -
  - onChannelOpenFailure
```
protected void onChannelOpenFailure()
```
    Called when the remote side fails to open a channel in response to our request. It only makes sense for some channel types to override this method. A local forwarding channel will never receive this message for example.
  - onRemoteClose
```
protected void onRemoteClose()
```
    Called when the remote side closes the channel. Override this method to change the default behaviour of instantly closing the channel unless there is buffered data remaining
  - isClosing
```
public boolean isClosing()
```
    Indicates whether the channel is currently performing a close operation
    
    Returns:
    
    boolean
  - close
```
public void close()
```
  - executeTask
```
protected void executeTask(ConnectionAwareTask task)
```
  - close
```
protected void close(boolean forceClose)
```
    This method closes the channel and free's its resources.
  - createCloseTask
```
protected ConnectionAwareTask createCloseTask(boolean forceClose)
```
  - onChannelFree
```
protected abstract void onChannelFree()
```
    This method is called when the channel has been closed and all its resources are no longer required.
  - createChannel
```
protected abstract byte[] createChannel()
                                 throws IOException
```
    Called when the channel is being created. You can return data to be sent in the channel open request, or null for none.
    
    Returns:
    
    byte[]
    
    Throws:
    
    IOException
  - openChannel
```
protected abstract byte[] openChannel(byte[] requestdata)
                               throws WriteOperationRequest,
                                      ChannelOpenException
```
    Called when the channel is being opened. You can retrun data to be sent in the channel open confirmation message, or null for none.
    
    Parameters:
    
    requestdata -
    
    Returns:
    
    byte[]
    
    Throws:
    
    WriteOperationRequest
    
    ChannelOpenException
  - onChannelOpenConfirmation
```
protected abstract void onChannelOpenConfirmation()
```
    Called when the channel has been confirmed as open by the remote side - this method is only called when the channel has been requested by this side of the connection
  - onChannelClosed
```
protected abstract void onChannelClosed()
```
    Called when the channel has been closed to enable resources to be freed.
  - onChannelOpen
```
protected abstract void onChannelOpen()
```
    Called when the channel has been opened - this method is only called when the remote side requests a channel open.
  - onChannelClosing
```
protected abstract void onChannelClosing()
```
    Called before the channel is closed
  - onChannelRequest
```
protected abstract void onChannelRequest(String type,
                                         boolean wantreply,
                                         byte[] requestdata)
```
    Called when a channel request is received.
    
    Parameters:
    
    type -
    
    wantreply -
    
    requestdata -
  - evaluateWindowSpace
```
protected abstract void evaluateWindowSpace(int remaining)
```
    Called to evaluate the window space available. Send a window adjust message if there if the minimum amount of space is not available.
    
    Parameters:
    
    remaining -
  - onRemoteEOF
```
protected abstract void onRemoteEOF()
```
    Called when the remote side reports its OutputStream as EOF.
  - sendEOF
```
protected void sendEOF()
```
    You can send EOF when you have no more data to send. The channel will still remain open until a close message is received.
  - markEOF
```
protected void markEOF()
```
  - canClose
```
protected boolean canClose()
```
    Can this channel close?
    
    Returns:
    
    true if there is no queued data, else false
  - onLocalEOF
```
protected abstract void onLocalEOF()
```
    Called when the local side is EOF.
  - isOpen
```
protected boolean isOpen()
```
    Get the open state of the channel.
    
    Returns:
    
    boolean
  - sendRequestResponse
```
protected void sendRequestResponse(boolean succeeded)
```
    Send a channel request.
    
    Parameters:
    
    succeeded -
  - sendWindowAdjust
```
protected void sendWindowAdjust(int count)
```
    Adjust the local window by adding more bytes.
    
    Parameters:
    
    count -

Class Channel

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

connection

localwindow

localWindowLock

Constructor Detail

Channel

Method Detail

isClosed

isEOF

getQueueSize

resetIdleState

clearIdleState

addEventListener

addInputListener

addOutputListener

getChannelType

getRemoteWindow

getLocalWindow

getLocalPacket

getRemotePacket

getLocalId

getRemoteId

queueSize

registerExtendedData

getSessionIdentifier

onWindowAdjust

getConnection

consumeWindowSpace

isSelfManagedWindowSpace

sendChannelData

sendChannelData

sendChannelData

sendChannelData

sendChannelDataAndBlock

getContext

sendExtendedData

sendExtendedData

onChannelData

onExtendedData

sendChannelRequest

onChannelOpenFailure

onRemoteClose

isClosing

close

executeTask

close

createCloseTask

onChannelFree

createChannel

openChannel

onChannelOpenConfirmation

onChannelClosed

onChannelOpen

onChannelClosing

onChannelRequest

evaluateWindowSpace

onRemoteEOF

sendEOF

markEOF

canClose

onLocalEOF

isOpen

sendRequestResponse

sendWindowAdjust