com.trilead.ssh2

Class Session

java.lang.Object

com.trilead.ssh2.Session

public class Session
extends Object

A Session is a remote execution of a program. "Program" means in this context either a shell, an application or a system command. The program may or may not have a tty. Only one single program can be started on a session. However, multiple sessions can be active simultaneously.

Version:

$Id: Session.java,v 1.2 2008/03/03 07:01:36 cplattne Exp $

Author:

Christian Plattner, plattner@trilead.com

Method Summary

Methods

Modifier and Type	Method and Description
void	close() Close this session.
void	execCommand(String cmd) Execute a command on the remote machine.
String	getExitSignal() Get the name of the signal by which the process on the remote side was stopped - if available and applicable.
Integer	getExitStatus() Get the exit code/status from the remote command - if available.
InputStream	getStderr()
OutputStream	getStdin()
InputStream	getStdout()
void	ping() This method can be used to perform end-to-end session (i.e., SSH channel) testing.
void	requestDumbPTY() Basically just a wrapper for lazy people - identical to calling requestPTY("dumb", 0, 0, 0, 0, null).
void	requestPTY(String term) Basically just another wrapper for lazy people - identical to calling requestPTY(term, 0, 0, 0, 0, null).
void	requestPTY(String term, int term_width_characters, int term_height_characters, int term_width_pixels, int term_height_pixels, byte[] terminal_modes) Allocate a pseudo-terminal for this session.
void	requestX11Forwarding(String hostname, int port, byte[] cookie, boolean singleConnection) Request X11 forwarding for the current session.
void	startShell() Start a shell on the remote machine.
void	startSubSystem(String name) Start a subsystem on the remote machine.
int	waitForCondition(int condition_set, long timeout) This method blocks until certain conditions hold true on the underlying SSH-2 channel.
int	waitUntilDataAvailable(long timeout) Deprecated. This method has been replaced with a much more powerful wait-for-condition interface and therefore acts only as a wrapper.

Methods inherited from class java.lang.Object

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

Method Detail

requestDumbPTY

public void requestDumbPTY()
                    throws IOException

Basically just a wrapper for lazy people - identical to calling requestPTY("dumb", 0, 0, 0, 0, null).

Throws:

IOException

requestPTY

public void requestPTY(String term)
                throws IOException

Basically just another wrapper for lazy people - identical to calling requestPTY(term, 0, 0, 0, 0, null).

Throws:

IOException

requestPTY

public void requestPTY(String term,
              int term_width_characters,
              int term_height_characters,
              int term_width_pixels,
              int term_height_pixels,
              byte[] terminal_modes)
                throws IOException

Allocate a pseudo-terminal for this session.

This method may only be called before a program or shell is started in this session.

Different aspects can be specified:

• The TERM environment variable value (e.g., vt100)
• The terminal's dimensions.
• The encoded terminal modes.

Zero dimension parameters are ignored. The character/row dimensions override the pixel dimensions (when nonzero). Pixel dimensions refer to the drawable area of the window. The dimension parameters are only informational. The encoding of terminal modes (parameter terminal_modes) is described in RFC4254.

Parameters:

term - The TERM environment variable value (e.g., vt100)

term_width_characters - terminal width, characters (e.g., 80)

term_height_characters - terminal height, rows (e.g., 24)

term_width_pixels - terminal width, pixels (e.g., 640)

term_height_pixels - terminal height, pixels (e.g., 480)

terminal_modes - encoded terminal modes (may be null)

Throws:

IOException

requestX11Forwarding

public void requestX11Forwarding(String hostname,
                        int port,
                        byte[] cookie,
                        boolean singleConnection)
                          throws IOException

Request X11 forwarding for the current session.

You have to supply the name and port of your X-server.

This method may only be called before a program or shell is started in this session.

Parameters:

hostname - the hostname of the real (target) X11 server (e.g., 127.0.0.1)

port - the port of the real (target) X11 server (e.g., 6010)

cookie - if non-null, then present this cookie to the real X11 server

singleConnection - if true, then the server is instructed to only forward one single connection, no more connections shall be forwarded after first, or after the session channel has been closed

Throws:

IOException

execCommand

public void execCommand(String cmd)
                 throws IOException

Execute a command on the remote machine.

Parameters:

cmd - The command to execute on the remote host.

Throws:

IOException

startShell

public void startShell()
                throws IOException

Start a shell on the remote machine.

Throws:

IOException

startSubSystem

public void startSubSystem(String name)
                    throws IOException

Start a subsystem on the remote machine. Unless you know what you are doing, you will never need this.

Parameters:

name - the name of the subsystem.

Throws:

IOException

ping

public void ping()
          throws IOException

This method can be used to perform end-to-end session (i.e., SSH channel) testing. It sends a 'ping' message to the server and waits for the 'pong' from the server.

Implementation details: this method sends a SSH_MSG_CHANNEL_REQUEST request ('trilead-ping') to the server and waits for the SSH_MSG_CHANNEL_FAILURE reply packet.

Throws:

IOException - in case of any problem or when the session is closed

getStdout

public InputStream getStdout()

getStderr

public InputStream getStderr()

getStdin

public OutputStream getStdin()

waitUntilDataAvailable

public int waitUntilDataAvailable(long timeout)
                           throws IOException

Deprecated. This method has been replaced with a much more powerful wait-for-condition interface and therefore acts only as a wrapper.

This method blocks until there is more data available on either the stdout or stderr InputStream of this Session. Very useful if you do not want to use two parallel threads for reading from the two InputStreams. One can also specify a timeout. NOTE: do NOT call this method if you use concurrent threads that operate on either of the two InputStreams of this Session (otherwise this method may block, even though more data is available).

Parameters:

timeout - The (non-negative) timeout in ms. 0 means no timeout, the call may block forever.

Returns:

• 0 if no more data will arrive.
• 1 if more data is available.
• -1 if a timeout occurred.

Throws:

IOException

waitForCondition

public int waitForCondition(int condition_set,
                   long timeout)

This method blocks until certain conditions hold true on the underlying SSH-2 channel.

This method returns as soon as one of the following happens:

• at least of the specified conditions (see ChannelCondition) holds true
• timeout > 0 and a timeout occured (TIMEOUT will be set in result conditions)
• the underlying channel was closed (CLOSED will be set in result conditions)

In any case, the result value contains ALL current conditions, which may be more than the specified condition set (i.e., never use the "==" operator to test for conditions in the bitmask, see also comments in ChannelCondition).

Note: do NOT call this method if you want to wait for STDOUT_DATA or STDERR_DATA and there are concurrent threads (e.g., StreamGobblers) that operate on either of the two InputStreams of this Session (otherwise this method may block, even though more data is available in the StreamGobblers).

Parameters:

condition_set - a bitmask based on ChannelCondition values

timeout - non-negative timeout in ms, 0 means no timeout

Returns:

all bitmask specifying all current conditions that are true

getExitStatus

public Integer getExitStatus()

Get the exit code/status from the remote command - if available. Be careful - not all server implementations return this value. It is generally a good idea to call this method only when all data from the remote side has been consumed (see also the method).

Returns:

An Integer holding the exit code, or null if no exit code is (yet) available.

getExitSignal

public String getExitSignal()

Get the name of the signal by which the process on the remote side was stopped - if available and applicable. Be careful - not all server implementations return this value.

Returns:

An String holding the name of the signal, or null if the process exited normally or is still running (or if the server forgot to send this information).

close

public void close()

Close this session. NEVER forget to call this method to free up resources - even if you got an exception from one of the other methods (or when getting an Exception on the Input- or OutputStreams). Sometimes these other methods may throw an exception, saying that the underlying channel is closed (this can happen, e.g., if the other server sent a close message.) However, as long as you have not called the close() method, you may be wasting (local) resources.