Class Session
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.-
Method Summary
Modifier and TypeMethodDescriptionvoid
close()
Close this session.void
execCommand
(String cmd) Execute a command on the remote machine.Get the name of the signal by which the process on the remote side was stopped - if available and applicable.Get the exit code/status from the remote command - if available.getStdin()
void
ping()
This method can be used to perform end-to-end session (i.e., SSH channel) testing.void
The same aspipeStdout(OutputStream)
except for stderr, not for stdout.void
Write stdout received from the other side to the specifiedOutputStream
.void
Basically just a wrapper for lazy people - identical to callingrequestPTY("dumb", 0, 0, 0, 0, null)
.void
requestPTY
(String term) Basically just another wrapper for lazy people - identical to callingrequestPTY(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
requestWindowChange
(int term_width_characters, int term_height_characters, int term_width_pixels, int term_height_pixels) Tells the server that the size of the terminal has changed.void
requestX11Forwarding
(String hostname, int port, byte[] cookie, boolean singleConnection) Request X11 forwarding for the current session.void
setWindowSize
(int newSize) Sets the receive window size.void
signal
(int code) Sends a signal to the remote process.void
Sends a signal to the remote process.void
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.
-
Method Details
-
requestDumbPTY
Basically just a wrapper for lazy people - identical to callingrequestPTY("dumb", 0, 0, 0, 0, null)
.- Throws:
IOException
-
requestPTY
Basically just another wrapper for lazy people - identical to callingrequestPTY(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.
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 benull
)- Throws:
IOException
-
requestWindowChange
public void requestWindowChange(int term_width_characters, int term_height_characters, int term_width_pixels, int term_height_pixels) throws IOException Tells the server that the size of the terminal has changed. SeerequestPTY(String, int, int, int, int, byte[])
for more details about how parameters are interpreted.- Parameters:
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)- Throws:
IOException
-
signal
Sends a signal to the remote process.- Throws:
IOException
-
signal
Sends a signal to the remote process. For better portability, specify signal by name, not by its number.- 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 serversingleConnection
- 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
Execute a command on the remote machine.- Parameters:
cmd
- The command to execute on the remote host.- Throws:
IOException
-
startShell
Start a shell on the remote machine.- Throws:
IOException
-
startSubSystem
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
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
-
getStderr
-
getStdin
-
pipeStdout
Write stdout received from the other side to the specifiedOutputStream
.By default, when data arrives from the other side, trilead buffers them and lets you read it at your convenience from
getStdout()
. This is normally convenient, but if all you are doing is to send the data to anotherOutputStream
by copying a stream, then you'll be end up wasting a thread just for this. In such a situation, you can call this method and let the I/O handling thread of trilead directly pass the received data to the output stream. This also eliminates the internal buffer used for spooling.When you do this, beware of a blocking write! If a write blocks, it'll affect all the other channels and sessions that are sharing the same SSH connection, as there's only one I/O thread. For example, this can happen if you are writing to
Socket
.If any data has already been received and spooled before calling this method, the data will be sent to the given stream immediately.
To signal the end of the stream, when the other side notifies us of EOF or when the channel closes, the output stream gets closed. If this is not desirable, you must wrap the output stream and ignore the
OutputStream.close()
call.- Throws:
IOException
-
pipeStderr
The same aspipeStdout(OutputStream)
except for stderr, not for stdout.- Throws:
IOException
-
waitUntilDataAvailable
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 thisSession
. 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 thisSession
(otherwise this method may block, even though more data is available).- Parameters:
timeout
- The (non-negative) timeout inms
.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
InterruptedException
-
waitForCondition
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 onChannelCondition
valuestimeout
- non-negative timeout in ms,0
means no timeout- Returns:
- all bitmask specifying all current conditions that are true
- Throws:
InterruptedException
- at least of the specified conditions (see
-
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 <code<WaitForCondition method).- Returns:
- An
Integer
holding the exit code, ornull
if no exit code is (yet) available.
-
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, ornull
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 theclose()
method, you may be wasting (local) resources. -
setWindowSize
public void setWindowSize(int newSize) Sets the receive window size. The receive window is a maximum number of bytes that the remote side can send to this channel without waiting for us to consume them (AKA "in-flight bytes"). When your connection is over a large-latency/high-bandiwdth network, specifying a bigger value allows the network to be efficiently utilized. OTOH, if you don't drain this channel quickly enough all those bytes in flight can end up getting buffered. This value can be adjusted at runtime.
-