com.sshtools.ssh2

Class Ssh2Channel

java.lang.Object

com.sshtools.ssh.message.SshAbstractChannel

com.sshtools.ssh2.Ssh2Channel

All Implemented Interfaces:

SshChannel, SshIO

Direct Known Subclasses:

Ssh2Session

public class Ssh2Channel
extends SshAbstractChannel

All terminal sessions, forwarded connections, etc are channels and this class implements the base SSH2 channel. Either side may open a channel and multiple channels are multiplexed into a single SSH connection. SSH2 channels are flow controlled, no data may be sent to a channel until a message is received to indicate that window space is available.

To open a channel, first create an instance of the channel as follows:

 Ssh2Channel channel = new Ssh2Channel("session", 32768, 32768);
 

The second value passed into the constructor is the initial window space and also the maximum amount of window space that will be available to the other side. The channel manages the window space automatically by increasing the amount available once the data has been read from the channels InputStream and only when the current value falls below half of the maximum.

After the channel has been created the channel is opened through a call to openChannel(Ssh2Channel channel). Once the channel is open you can use the IO streams to send and receive data.

Author:

Lee David Painter

Field Summary

Fields

Modifier and Type	Field and Description
static String	SESSION_CHANNEL

Fields inherited from class com.sshtools.ssh.message.SshAbstractChannel

CHANNEL_CLOSED, CHANNEL_OPEN, CHANNEL_UNINITIALIZED, channelid, manager, ms, state

Constructor Summary

Constructors

Constructor and Description
Ssh2Channel(String name, int windowsize, int packetsize) Construct an SSH2 channel

Method Summary

Methods

Modifier and Type	Method and Description
void	addChannelEventListener(ChannelEventListener listener) Provides an event listening mechanism.
protected void	channelEOF() Called when the remote side data stream is EOF, by default this method does nothing
protected void	channelRequest(String requesttype, boolean wantreply, byte[] requestdata) Called when a channel request is received, by default this method sends a failure message if the remote side requests a reply.
protected void	checkCloseStatus(boolean remoteClosed)
void	close() Closes the channel.
protected byte[]	create() Called after the channel has been created by the	protected com.sshtools.ssh2.Ssh2Channel.ChannelInputStream	createExtendedDataStream() Currently reserved.
boolean	equals(Object obj) This channel is equal to another channel if the channel id's are equal.
InputStream	getInputStream() Get an InputStream to read incoming channel data.
protected SshMessageStore	getMessageStore()
String	getName() Get the name of the channel.
OutputStream	getOutputStream() Get an OutputStream to write outgoing channel data.
protected MessageObserver	getStickyMessageIds()
void	idle()
boolean	isSendKeepAliveOnIdle()
protected void	open(int remoteid, long remotewindow, int remotepacket) Called once an SSH_MSG_CHANNEL_OPEN_CONFIRMATION has been sent.
protected void	open(int remoteid, long remotewindow, int remotepacket, byte[] responsedata) Once a SSH_MSG_CHANNEL_OPEN_CONFIRMATION message is received the framework calls this method to complete the channel open operation.
protected boolean	processChannelMessage(SshChannelMessage msg) Processes channel request messages by passing the request through to channelRequest() .
protected void	processExtendedData(int typecode, int length, SshChannelMessage msg) Called when extended data arrives.
protected void	processStandardData(byte[] buf, int off, int len)
protected void	processStandardData(int length, SshChannelMessage msg) Called when channel data arrives, by default this method makes the data available in the channels InputStream.
boolean	sendRequest(String requesttype, boolean wantreply, byte[] requestdata) Sends a channel request.
boolean	sendRequest(String requesttype, boolean wantreply, byte[] requestdata, boolean isActivity) Sends a channel request.
void	setAutoConsumeInput(boolean autoConsumeInput) Automatically consume input data
void	setSendKeepAliveOnIdle(boolean sendKeepAliveOnIdle)

Methods inherited from class com.sshtools.ssh.message.SshAbstractChannel

getChannelId, getMessageRouter, init, isClosed

Methods inherited from class java.lang.Object

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

Field Detail

SESSION_CHANNEL

public static final String SESSION_CHANNEL

See Also:

Constant Field Values

Constructor Detail

Ssh2Channel

public Ssh2Channel(String name,
           int windowsize,
           int packetsize)

Construct an SSH2 channel

Parameters:

name - the name of the channel, for example "session"

windowsize - the initial window size

packetsize - the maximum packet size

Method Detail

getStickyMessageIds

protected MessageObserver getStickyMessageIds()

Specified by:

getStickyMessageIds in class SshAbstractChannel

setAutoConsumeInput

public void setAutoConsumeInput(boolean autoConsumeInput)

Description copied from interface: SshChannel

Automatically consume input data

Parameters:

autoConsumeInput - boolean

getMessageStore

protected SshMessageStore getMessageStore()
                                   throws SshException

Overrides:

getMessageStore in class SshAbstractChannel

Throws:

SshException

getName

public String getName()

Get the name of the channel.

Returns:

the name of the channel.

getInputStream

public InputStream getInputStream()

Description copied from interface: SshIO

Get an InputStream to read incoming channel data.

Returns:

the channels InputStream

getOutputStream

public OutputStream getOutputStream()

Description copied from interface: SshIO

Get an OutputStream to write outgoing channel data.

Returns:

the channels OutputStream

addChannelEventListener

public void addChannelEventListener(ChannelEventListener listener)

Description copied from interface: SshChannel

Provides an event listening mechanism.

isSendKeepAliveOnIdle

public boolean isSendKeepAliveOnIdle()

setSendKeepAliveOnIdle

public void setSendKeepAliveOnIdle(boolean sendKeepAliveOnIdle)

idle

public void idle()

Overrides:

idle in class SshAbstractChannel

create

protected byte[] create()

Called after the channel has been created by the Returns:

data that should be returned in the SSH_MSG_CHANNEL_OPEN_CONFIRMATION message

Throws:

IOException

open

protected void open(int remoteid,
        long remotewindow,
        int remotepacket)
             throws IOException

Called once an SSH_MSG_CHANNEL_OPEN_CONFIRMATION has been sent.

Parameters:

remoteid -

remotewindow -

remotepacket -

Throws:

IOException

open

protected void open(int remoteid,
        long remotewindow,
        int remotepacket,
        byte[] responsedata)
             throws IOException

Once a SSH_MSG_CHANNEL_OPEN_CONFIRMATION message is received the framework calls this method to complete the channel open operation.

Parameters:

remoteid - the senders id

remotewindow - the initial window space available for sending data

remotepacket - the maximum packet size available for sending data

responsedata - the data returned from the remote side in the SSH_MSG_CHANNEL_OPEN_CONFIRMATION message

Throws:

IOException

processChannelMessage

protected boolean processChannelMessage(SshChannelMessage msg)
                                 throws SshException

Processes channel request messages by passing the request through to channelRequest() .

Specified by:

processChannelMessage in class SshAbstractChannel

Throws:

SshException

processStandardData

protected void processStandardData(int length,
                       SshChannelMessage msg)
                            throws SshException

Called when channel data arrives, by default this method makes the data available in the channels InputStream. Override this method to change this behaviour.

Parameters:

buf -

offset -

len -

Throws:

IOException

SshException

processStandardData

protected void processStandardData(byte[] buf,
                       int off,
                       int len)
                            throws SshException

Throws:

SshException

processExtendedData

protected void processExtendedData(int typecode,
                       int length,
                       SshChannelMessage msg)
                            throws SshException

Called when extended data arrives. This method fires the com.sshtools.ssh.ChannelEventListener#extendedDataReceived(com.sshtools.ssh.Channel, byte[], int, int, int) event so to maintain code compatibility always call the super method in any overidden method.

Parameters:

typecode - the type of extended data

buf - the data buffer

offset - the offset

len - the length

Throws:

SshException

IOException

createExtendedDataStream

protected com.sshtools.ssh2.Ssh2Channel.ChannelInputStream createExtendedDataStream()

Currently reserved.

Returns:

ChannelInputStream

sendRequest

public boolean sendRequest(String requesttype,
                  boolean wantreply,
                  byte[] requestdata)
                    throws SshException

Sends a channel request. Many channels have extensions that are specific to that particular channel type, an example of which is requesting a pseudo terminal from an interactive session.

Parameters:

requesttype - the name of the request, for example "pty-req"

wantreply - specifies whether the remote side should send a success/failure message

requestdata - the request data

Returns:

true if the request succeeded and wantreply=true, otherwise false

Throws:

IOException

SshException

sendRequest

public boolean sendRequest(String requesttype,
                  boolean wantreply,
                  byte[] requestdata,
                  boolean isActivity)
                    throws SshException

Sends a channel request. Many channels have extensions that are specific to that particular channel type, an example of which is requesting a pseudo terminal from an interactive session.

Parameters:

requesttype - the name of the request, for example "pty-req"

wantreply - specifies whether the remote side should send a success/failure message

requestdata - the request data

isActivity -

Returns:

true if the request succeeded and wantreply=true, otherwise false

Throws:

IOException

SshException

close

public void close()

Closes the channel. No data may be sent or receieved after this method completes.

checkCloseStatus

protected void checkCloseStatus(boolean remoteClosed)

equals

public boolean equals(Object obj)

This channel is equal to another channel if the channel id's are equal. Please note that channel numbers may be reused so this method should only be called on open channels.

Overrides:

equals in class Object

channelRequest

protected void channelRequest(String requesttype,
                  boolean wantreply,
                  byte[] requestdata)
                       throws SshException

Called when a channel request is received, by default this method sends a failure message if the remote side requests a reply. Overidden methods should ALWAYS call this superclass method.

Parameters:

requesttype - the name of the request

wantreply - specifies whether the remote side requires a success/failure message

requestdata - the request data

Throws:

IOException

SshException

channelEOF

protected void channelEOF()

Called when the remote side data stream is EOF, by default this method does nothing

Throws:

IOException